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*** Please note: This website (comp-hist) was completed before I found out about
Wikipedia in 2002.
Since then I have added material occasionally.
Items are certainly not complete, and may be inaccurate.
Your information, comments, corrections, etc. are eagerly requested.
Send e-mail to Ed Thelen.
Please include the URL under discussion. Thank you ***
Warning - a tirade follows -
I love Wikipedia. Give it over $100/year. Use it a lot -
BUT - for better or worser,
it lets seemingly any "idiot" update its web pages.
On Sept 19,20221, in
https://en.wikipedia.org/wiki/LGP-30#Design was the sentence
"It also had an integer multiplication but, because the accumulator had 32 bits while memory words had only 31 bits, only even integers could be thus represented."
This "old wives tale" pops up now and again.
The "32 bit accumulator" is one of the recirculating registers on the drum,
and has 31 used bits just as any other drum resident.
You can as a matter of fact multiply odd integers naturally.
This idiot removed the quoted sentence - lets see if some other idiot adds it back in ??
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Latest addition - DICTATOR - Wed 8/11/2021
LGP-30
Manufacturer | Royal Precision Electronic Computer Company
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Identification,ID | LGP-30 (Librascope General Precision)
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Date of first manufacture | 1956
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Number produced | about 500 (Professor Smilie)
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Estimated price or cost | $47,000 - see Dartmouth College Price
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Contents of this page:
Photo
Placard
from Placard in Computer History Museum (2008)
"The LGP-30 was a small drum-based computer marketed to engineering, scientific and educational users.
Among the first desk-sized computers, the LGP-30 offered small-scale scientific computing for a relatively low price.
It had 113 vacuum tuves and 1,450 diodes, used conventional office power and required no air conditioning.
The machine proved to be very reliable and many LGP-03s were in use fo over a decade.
"Speed: 500 Add/s "
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from 1981 inventory of Computer History Museum
LGP-30 - Librascope General Precision Computer
Word Length: 31 Bits, including a sign bit,
but excluding a blank spacer bit
Memory Size: 4096 words
Speed: 0.260 milliseconds access time between two
adjacent physical words; access times between two
adjecent addresses 2.340 milliseconds.
Clock Rate: 120 Khz
Power: 1500 watts
Arithmetic element: Three working registers: C the
counter register, R the instruction register and A the
accumulator register.
Instruction format: Sixteen instruction using half-word
format
Technology: 113 vacuum tubes and 1350 diodes.
Number Produced; 320~493
First Delivery: September, 1956
Price: $47,000
Successor: LGP-21
Achievements: With the Bendix G-15 the first of the
desk-sized computers offering small scale scientific
computing. Revolutionizing the computer industry with
the potential for low-cost distributed processing.
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Architecture
Description from
BRL - REPORT N0. 1115, MARCH 1961
Bit serial, binary, 31 bit word computer with 4096 word drum. (Many references refer
to the LGP-30 as having a 32 bit word. However, the 32nd bit is always read from
the drum as a zero, so let us clarify and say 31 useful data and instruction bits.)
Standard inputs were the
Flexowriter keyboard and
paper tape (10 6 bit characters/second).
The only printing output was the Flexowriter printer (typewriter, 10 characters/second).
An optional higher speed paper tape reader and punch was available as a
separate peripheral.
Interesting address location (successive addresses on drum are 7 physical
locations further on) helped reduce rotational latency for instruction
access. (Instructions with out memory operands could be executed much
faster than one per drum revolution.) This is now called "interlacing"
and is discussed in
The LGP-30 and LGP-21
There were 32 bit locations per drum word, but only 31 were used, permitting
a "restoration of magnetic flux in the head" at the 32nd bit time. (I never
understood why the 32nd bit was not used for parity checking - there was
no drum validity checking.) A utility could be run to map defective locations
on the drum, and advise users and loaders of the defective tracks, but marginal
and failing drums caused interesting problems.
From Joseph H. Austin Computer Science,
St. Augustine's College, Raleigh NC - August 2003
I found the reference elsewhere, and thought you might like to add it [or
copy of the paper if you can get it] to your site:
REF: Stanley Frankel, The logical design of a simple general purpose
computer, Trans.I.R.E. Professional Group on Electronic Computers, EC-6/1,
Mar 1957
This paper describes what became the LGP-30 from the architectural point of
view, and includes the complete boolean logic formulas for all the
operations.
As a graduate student in computer science at U North Carolina Chapel Hill in
the late 60's, I was taking a computer architecture class under Dr. Fred
Brooks [IBM/360; The Mythical Man-Month]. He assigned each student to read
the paper and work through one of the instructions, cycle by cycle and bit
by bit. As I recall, I did multiply. For anyone interested in
understanding the workings of a computer from the AND/OR/NOT level up, this
[is] the one paper to study.
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In Dec 2019 I found the following:
This
website provides a link to the PDF of Stanley's paper.
local PDF of from that web site.
Also a local copy of a paper referencing the above
here by Keith Smillie -
"Programming Then and Now: From the LGP-30 to the Laptop"
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Special features
from
LGP-30 PHYSICAL DESCRIPTION
LGP-30 PHYSICAL DESCRIPTION
The LGP-30 is commonly referred to as a desk computer.
Obviously, this phrase originated because the size of the LGP-30 closely
parallels the size of a standard office desk. The LGP-30 is 26" deep,
33" high, and 44" long, exclusive of the typewriter shelf. The
computer weighs approximately 800 pounds and is mounted on sturdy casters
which facilitates movement of the computer.
Another asset in regard to the computer's mobility is its power requirement.
The LGP-30 requires 1500 watts when operating under full load. The power
inlet cord may be plugged into any standard 115 volt 60 cycle single phase
line. The computer contains internal voltage regulation of all voltages
against power line variations from 95 to 130 volts. In addition to regulation
of power line variations, the computer also contains the circuitry required
to permit a warm-up stage. This warm-up stage minimizes thermal shock to
tubes and insures long component life. The computer contains its own blower
unit and directs filtered air, through ducts, to tubes and diodes, in order
to again insure long component life and proper operation. No expensive
air conditioning needs to be installed ,if the room is kept within a reasonable
temperature range.
The computer contains 113 electronic tubes and 1450 diodes. The 113 electronic
tubes are mounted on 34 etched circuit pluggable cards which also contain
associated components. Although 34 pluggable cards are used, there are
only 12 different types of such cards. Card-extenders are available to
permit dynamic testing of all machine functions. Six hundred and eighty
of the 1450 diodes are mounted on one pluggable logic board. This logic
board may be quickly removed and is very accessible for service personnels
use.
The main memory consists of a magnetic drum that contains 4096 words. An
instruction or data word may be stored in each one of the 4096 available
words. When instructions are placed on the drum, they will be executed
in sequence until one of the instructions "transfers control"
to a new set of instructions.
...
The LGP-30 had 16 instructions
OP-CODE | SYMBOL | FUNCTION | ||
| OP-CODE | SYMBOLFUNCTION
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| 0000 Z STOP | ||
| 1000 P PRINT
0001 B BRING | ||
| 1001 E EXTRACT
0010 Y STORE ADDRESS | ||
| 1010 U UNC-TRANSFER
0011 R RETURN ADDRESS | ||
| 1011 TTEST
0100 I INPUT | ||
| 1100 H HOLD
0101 D DIVIDE
(rounded)
| ||
| 1101 C CLEAR
0110 N MULTIPLY | ||
| 1110 A ADD
0111 M MULTIPLY | ||
| 1111 S SUBTRACT
http://computermuseum.informatik.uni-stuttgart.de/dev_en/lgp30/lgp30_1.html
states "Each opcode is represented by a letter. The binary code of the instruction
corresponds to the code of the letter of the flexowriter with the two most
significant bits being ignored. The ASCII wasn't invented, yet. The keyboard
on the picture shows 16 white keys: these are the letters assigned to an opcode.
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The LGP-30 had a "Pseudo" 32 bit accumulator
which was stored on the drum memory. Actually it had 32 such accumulators
on one track of the drum and in the multiplication functions a 64 bit product
was stored. The 'M' or 0111 multiply would give you the first 32
bits of the product while the 'N' or 0110 multiply would work the
last 32 bits.
All calculations were in pure binary. Real values were
faked as integer and the programmer had to take care of the bit point or
the 'Q' for each value.
There was a small CRT display which was used for debugging.
The display was in binary and consisted of three registers. {To read you
counted the ups and downs of the trace.}
Location Counter
Last Instruction executed
Accumulator
from Ed Thelen
This machine was about as serial as possible, The accumulator and
(? other registers ?) were recirculated on the drum. To ADD
from (drum) memory to the accumulator, the machine would wait until the
(drum) memory rotated to the desired location, then add, bit-by-bit
read/writing from/to the accumulator.
A neat trick was the hardware optimization data/instruction locations.
The 31 bit signed data word could handle the range of +- 536,870,911.
The floating point format used in floating point subroutines, an arithmetic
interpreter, and the ACT-III compilier handled the range of
0.10000002 <= |n| <= 0.9999999994
with an exponent of
-32 <= e <= +31
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Oddly, the floating point format did not exactly represent the number 1.
- and
The LGP-30 did not have an index register, not indexing capability.
This limitation made self-modifying code (a current no-no) a requirement.
To search a list of words, part of the program loop modifies the
address part of the "bring from memory" - "b" instruction.
Indeed, there is a special instruction to change only the address
part of an instruction so that you are less likely to make a mistake.
- and
The LGP-30 divide rounds the quotient and can cause problems.
No instruction yields the remainder of a divide, it must be calculated
The following can detect if a rounding has occurred.
"DND" is dividend, "DVR" is divisor, "QNT" is quotient, "RMD" is remainder
assuming all above input values are positive
RMD = DND-(DVR*QNT)
if ((RMD) < 0) {
"rounding has occurred"
subtract one from QNT
recompute RMD = DVR + RMD
}
from Ray Borrill
There is one thing you did not mention in your list of [optional]
goodies for the computer. That is the "high speed" tape reader and punch. The reader
ran at 60 CPS and the punch at 20 CPS
from Mark Greenia - August 2015 - see YouTube videos
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Just found out what the boards are from. An early Librascope LGP-30 machine.
[??? the 2D21 thyratrons,left, are these for driving the Friden Flexowriter ???]
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Mark Greenia kindly sent the following circuit card to Ed Thelen, as a souvenir -
A "TRIPLE FLIP FLOP 309653" - Holds three bits, all tubes are 5687. This unit uses about 25 watts.
| "Front" or tube side. Note the little neon tubes (? NE-2 ?) by the vacuum tubes,
maybe to visually show the state of the flip-flop or bit. Each tube
uses about 10 watts to operate, 5.5 watts for the filament alone.
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| "Back" side. Note: a) The small red capacitors are used to speed up the logic,
help fight the other capacitances.
b) The tiny black glass diodes.
c) Each large resistor is rated at 2 watts, running at maybe 0.5 watts
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For vacuum tube logic geeks, here is the schematic
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- (left circuit) Inputs C and E are edge triggered
- logic levels are clamped -20 to 0 volts, outputs B and F
- C1 and C5 are speed up capacitors
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Most of the amplifier/logic tubes in an LGP-30 are:
- 5687 - a miniature, medium-mu (~gain) twin triode for use in general-purpose amplifier
- 5915 - a heptode logic switching tube: both control grids at 0 V = tube conducts, control grid #1 OR control grid #3 at negative voltage: tube blocked
- 5965 - a miniature, high-mu (~gain) twin triode for use in general-purpose amplifier
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Cory Heisterkamp Purchased an LGP-30 and sent these pictures
to the newsgroup classiccmp.org
He wrote: "I'm far from an expert, but it certainly looks like an oxide coating
to me. I'm reminded of the folklore when IBM was developing the RAMAC
and finally had success with a magnetic paint mixed up outside of house.
In that case it was easy to apply...just spin up the disc and pour!
"
There are a couple of 1" long spots where the coating was scraped away and
the heads relocated. Given what I've read about the Control Data badged LGP-30's,
this was likely a refurb sold in the 60's. The replacement heads certainly
support that. Below are some pics of my drum; the tonewheel clock generator
can be seen at the far right. The groove just to the left of that leaving a
single band in the mag material is too perfect to be a goof, but at the 0.4"
head offset spacing, is too narrow to contain more than one track. -C"
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Some further detective work found a leaky 1500uF cap in one of the B+ supplies which was causing the 'surging' issue on the scope. For good measure I replaced all six 1500 and 3000uF caps even though ripple was low. Better safe than sorry and if it means pulling that chassis and its covers again, all the better. I attempted to weigh it on my shipping scale, but it only registers to 100 lbs and the indicator flew right past that.
There had been a small thermal event in the AC junction box that the twist lock connector mounts to, and I suspect it occurred pre-60's refurb. It's not too surprising as the wiring on the computer side is aluminum and the feed is copper. The box needed replacing but was a unique Hubbell variation of a std 4" box with special ears. I couldn't find anything even close to that at any of the supply houses online, probably because it violates today's conductor fill rules (it's only 1" deep but the socket consumes most of that depth and 75% of the area). I eventually settled on drilling/tapping a standard box and cleaned up the wiring.
The sequencer unit is now working correctly after I found an NOS relay to R&R contacts with. The blower is still steady and quiet with its new bearings, and no issues (knock on wood) with the drum after greasing the end bearing, belt and 'tightening' up the tolerances on the timing and short register heads.
Some good news- I now have three horizontal lines on the scope, rock solid and where they should be. I can get the occasional pattern for Instruction contents, but Order and Accumulator still aren't reading/writing/displaying. All in good time.
http://radar58.com/LGP30/wp-content/uploads/2017/03/lgp.jpg
Even better news is that the three timing tracks appear to be intact on the drum and the supporting hardware is working.
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More from Cory Heisterkamp - Dec 18, 2017
Around 11 months ago to the day I was busy recapping these modules. Most of the micas were
good, but all the electrolytic and wax caps had to go. That task taught me a couple of things.
Having a machine that was 'reconditioned' by Control Data, I had a mix of boards that spanned
early production to late, and the PCB trace quality improved dramatically from the early ones.
Also, the set of schematics on the net are comprised of scans from different revision levels
all rolled in to one. When checking component value to the print 1 for 1, I'd occasionally
find small differences; this where having multiples of the same module came in handy for
comparison.
In the attached pic, you'll note two different versions of the same module,
both having the identical part number stamped on them.
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Historical Notes
from Jürgen Müller - Dec 2017
Meanwhile, here’s a little quiz courtesy of an unknown ebay seller: Which computers are behind models “A” to “D”, which Royal McBee considered to be the main competitors for the LGP-30 in 1958? ;-)
Merry Christmas to everyone!
Juergen
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Ad
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Hints from Ed Thelen
from W Van Snyder - Feb 2017
"LGP" stands for "Librascope General Precision." Librascope was founded
in Glendale, CA, in 1937, and bought by General Precision in 1941. It
was bought by Singer, which was bought by corporate raider Paul
Bilzerian, then sold to Loral, then Lockheed Martin. It's now Lockheed
Martin NE&SS - Undersea Systems.
In the 1950's and 1960's, they specialized in fire-control computers for
torpedos. The LGP-30 was a general-purpose computer, not a
special-purpose military computer. "LGP" was an acronymic pun, meaning
both "Librascope General Precision" and "Librascope General Purpose."
In about 1961, my father was the liaison engineer from Honeywell
Ordnance Division for Librascope's work on the fire-control computers
for two projects, called ASROC (Anti-Submarine Rocket) and RAT
(Rocket-Assisted Torpedo). He would bring home drawings the size of the
dinner table, with diode gate circuits all over them, and check them. I
assume I wasn't supposed to see them, but I was only 14 years old. The
fire-control computers for ASROC and RAT were probably not based on the
LGP-30. He told a story of a test shot of ASROC off San Clemente
Island. After the shot the test torpedo was supposed to surface so they
could retrieve it and use it again. It didn't, so they were sure the
shot had failed and they'd lost it. Then the target diesel submarine,
which had a fiberglass sail so it looked like a nuclear submarine,
surfaced with the torpedo stuck through the sail. So the test worked
quite well.
According to http://www.silogic.com/Athena/Athena.html (and
history.nasa.gov) the computer on the Centaur upper stage was a
Librascope 3, a 25-bit drum computer. Maybe it was based on the LGP-30.
Van
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from David Hartke July 25, 2008
In 1962 I had the distinct pleasure to come to know Stan Frankel in a business
capacity. At the time I was working for a company called CSC (Consolidated Systems Corp.)
in Monrovia. A couple of us had designed a micro-programmed computer along the lines of
Wilkes. I was asked to get someone to critique the design and Frankel’s name came up.
I consider him to be one of the most brilliant people I have ever met. One of the things
that really impressed me was his ability to approach things from basics. Not sure but I
think he would often start out with “well the charge of an electron is …..”. Another thing
I remember was his work on solving the detergent soap bubble problem. He and a Chinese
guy (I think) wrote a book about soap bubbles and that work, at least in part, led to the
design of a better detergent soap in which the soap bubbles would collapse over time so
as to not plug up sewage treatment facilities. I also remember that the first day he
came to meet me: he came in looking like a bum directly off the streets in downtown L.A.!
I am pretty sure he had not shaved in a day or two. And to complete the picture I
remember he brought in his cigarette rolling machine. Then, all during our
conversation/work he would frequently stop to roll his own cigarettes.
Of course, his design of the LPG30 was extremely impressive to me. I always have said that
that machine was truly the first personal computer. Of course, the $10K [???] price
tag probably makes some people take issue with that statement. Perhaps the main reason I
wanted to write to you was to ask you how many flip-flops the machine had. My memory says
there were a total of only seven, which, of course, is remarkable, if true. Could you verify that?
wikipedia says 15 - I don't have schematics - Ed Thelen
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from Bill Bryner (Sept 11, 2007)
My name is James William (Bill) Bryner. I programmed the LGP-30 for
Douglas Aircraft Company in 1959. That was during the testing of the
DC-8. In 1960 I was hired by Royal-McBee to write the assembler for the
replacement to the LGP-30, the RPC-4000. Royal-McBee was the company
that produced Royal typewriters and McBee business data forms. They had
joined with Librascope, a division of General Precision, to market the
LGP-30 and later the RPC-4000.
Mel Kaye designed the RPC-4000 assembler. It was titled ROAR
(Royal-McBee Optimizing Assembler Routine). Edward W. Dubbs and I
programmed that assembler. Following that, I wrote an LGP-30 simulator
to run on the RPC-4000. This was meant to allow all programs written
for the LGP-30 to be executed on the RPC-4000 without further
programming. A drum computer simulating a drum computer is agonizingly
slow!
General Precision was responsible for the hardware and Royal-McBee was
responsible for the programming, marketing and schooling relating to
those computers. The programming offices and school of Royal-McBee were
located on Cahuenga Blvd. between Sunset Blvd. and Selma Ave. They were
placed there because the sales people felt the Hollywood location would
attract sales by people wanting to go to school in Hollywood.
I hope this information will be of interest to you. If you have any
further questions I will be glad to try to answer them.
Bill Bryner
Received Sept 5 2017
Steve Leibson writes [October 2004]
"Through the San Jose library's inter-library loan program, I just got a
copy Stan Frankel's article on MINIAC and the LGP-30 published in the
IRE's Computer Proceedings in 1956. The article states that Frankel's
MINIAC was built at CIT and that it served as a prototype for the
Librascope LGP-30, which has essentially the same hardware as MINIAC
including the drum-memory-based register system. Does that jive with
your understanding of MINIAC, Marchant Research, and Atlantic Refining?
Neither Marchant nor Atlantic are mentioned in Frankel's article."
For a fascinating story of designer of the LGP-30, click
Stanley P. Frankel,
Unrecognized Genius
from Ed Thelen
It is interesting to view the web sites of early users - such as
The Computer and Me
and LGP-30
by Keith Smillie.
The LGP-30, The University of Alberta's first computer, had no compilier and
no floating point routines
the early days. Using it for serious work must have been "interesting".
In college in 1959, an LGP-30 arrived with an interesting compilier called ACT-III
which I used before I heard of FORTRAN.
Here is the manual, copied from that wonderful
bitsavers.org.
When I later used FORTRAN,
there was about a 1 to 1 statement similarity except for the
FORMAT operations, which seemed easier in ACT-III.
And ACT-III handled mixed mode (integer and floating point)
much better than the FORTRAN of the day. In the early FORTRANs
you had to be VERY careful about converting operands to compatable
formats when you wanted to multiply a floating
point number by an integer. ACT-III just went ahead and "did the right thing".
FORTRAN seems to have been very user unfriendly in that respect for a long time.
There was also a symbolic assembler that was convenient.
The compilier took (? 10 minutes ?) to read onto drum from the
Frieden Flexowriter, but once installed was good for
compile and run for days or until you loaded some other program.
The floating point was "reasonably" quick. I simulated a tube based
analog multiplier (the analog multiplier used pulse width modulation)
through a large variety of wave forms,
frequencies relative to the pulse width frequency,
and other conditions over a LONG (no sleep) weekend.
from Kathi Cole
... and my dad, Charles "Charlie" Cole
went to work for Louis Imm of Librascope in 1941,
as a tool and die maker. He started working for Mr. Imm
just after the first Glendale, CA plant location was opened,
which I believe was on Sonora Street, near the then-existing
Glendale Airport.
... he eventually became production control manager
for Librascope. I can remember him talking about the purchase
by General Precision, and later by the Singer Corporation
- both of which companies are now defunct, I believe.
I've been trying to trace the chronology of the company
through searches on the Internet, which is how I found your site.
At some point I understand Singer Corporation sold Librascope to
Loral, who had it in their Federal Systems-Manassas business unit,
which was then bought by Lockheed Martin in April of 1996,
and in 1997 closed the Glendale facility and moved operations
to Virginia, thereby ending a 50-year history of the company
being a good-sized employer in the Southern California aerospace industry.
If you have any resources you could refer me to for researching
the last 20 years of Librascope history, I'd sure appreciate hearing
from you.
A Software Story
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This Artifact
Interesting Web Sites
- The role of an LGP-30 in Dartmouth Basic
- the original BASIC - starts at 10 minutes
- LGP-30 — A Drum Computer of Significance
by Norbert Landsteiner < n . landsteiner @ masswerk . at > July 23, 2019
- Cory Heisterkamp has purchased a LGP-30 from Canada, and is starting to work :-))
A Youtube of the flexowriter restoration,
and a blog - "LGP-30 Restoration" - blog - Feb 2017
-
LGP-30 by Computermuseum der Fakultät Informatik - Jan 2017
-
simulating an LGP-30, suggested by
Cory Heisterkamp, who just purchased and is restoring one - Jan 2017
- a thread about
simulating an LGP-30 advice via cctech@classiccmp.org - Dec 2016
-
Librascope Memories, suggested by Tony Cappellini
August 2016
- YouTube
LGP 30 (and the development of BASIC) at Dartmouth Jan 2016
- YouTube
LibraScope LGP-30 Computer - Vintage Computing Tube Circuits August 2015
- YouTube Warming up the LGP-30 August 2015 -
Youtube showing active CRT, Flexowriter being keyed and typing,
Flexowriter reading paper tape (10 char/sec)
- BALLISTIC RESEARCH LABORATORIES, REPORT N0. 1115, March 1961,
"A THIRD SURVEY OF DOMESTIC ELECTRONIC DIGITAL COMPUTING SYSTEMS"
- LGP-30 Programming Manual, HTML (local)
and .pdf (bitsavers)
-
LGP30_OperationsManual from bitsavers.org
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Flexowriter Information
-
LGP-30 in German
-
The LGP-30 -- Bob's first computer! By, and permission
granted by,
Robert Lilley (e-mail address updated) and two
images of hexadecimal (almost binary) filled in coding sheets copied from
the web site (in case it disappears!)
- - "Here's a Mel Kaye original!"
- - "Mel's unique initials signature."
(FORTRAN and COBOL were being developed about this time.)
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The LGP-30 and LGP-21
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Essays on Early Computers (LGP-30)
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Computer Program written in Act III for the LGP-30
- "Computer Structures: Readings and Examples", (1971 edition) by C. Gordon Bell & Allen Newell Part 3, Section 2, Chapter 16
- LGP-21 by Tom Jennings
(Spring 2003) - see
restorations.html#LGP-21 "I'm looking for software (LGP-30 or
LGP-21)."
-
"Lest a Whole New Generation of programmers Grow up in Ignorance of this Glorious Past...",
local copy,
Wikipedia commentary,
-
Detailed images of LGP-30 internals added May 2014
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Other information
- LGP-30 Supplement from an LGP-30 Maintenance Manual
on line from Germany
- On-line manual LGP-30 Programming Manual by
Royal McBee Corporation
- On-line manual "LGP-21 Programming Manual"
From Bob Supnk
":
The LGP-21 and LGP-30 are not program compatible;
not even upward or downward compatible. The LGP-21's non-IO instructions
are either the same as the -30, or add some new features (like overflow
flag and Z skips); but the I/O instructions are completely different. The
LGP-21 has "IO device addresses" in the IO instructions; the LPG-30 has
data (or nothing) in the IO instructions, and the IO device selection is
done by manual switches. The -21 stalls on output; the -30 must be
correctly timed or manually stalled or it will lose data."
Chapter | topic |
TOC | Table of Contents |
1 | Introduction to the LGP-21 |
2 | The LGP-21 Command Structure |
3 | Construction of an LGP-21 Program |
4 | Binary Number System |
5 | Number Scaling for the LGP-21 |
6 | INPUT/OUTPUT |
7 | Program Tape preperation |
8 | Timing and Optimization |
Appx A | Computer Control Panel |
Appx B | INPUT/OUTPUT Unit Controls |
Appx C | Various tables
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- A Working LGP-30 see
restorations.html#LGP-30
An e-mail from
Klemens Krause November 26, 2002 to
Arnold G. Reinhold
I just found 'your' programming example for the LGP-30 written in ACT
III
(again):
http://world.std.com/~reinhold/comp-hist/actiiisample.html
I have a running LGP-30 with some original software. For example the
ACT V - compiler. I have also the ACT I and ACT V documentation and
an annotation about the differences between ACT III and ACT V.
So I think I can do some remarks about the programming example from
Arnold G. Reinhold.
First there is a typing error in line 5: After label s2 the apostrophe
is missing. (Sorry, very trivial).
Then obviously the program was not complete at compile time. The last
line
daprt'p'e'r'i'o'd' 'i's'
makes no sense. This is obvious. But whats not obvious: ACT programs
are finished by three apostrophs.
A last line in an ACT-program thus could be
stop'''
or
use's1''' (to return to the begin.)
The symbol table with the four undeclared labels s000 to s040 shows
that the program was incomplete at compiletime.
Third, the line
f 0730
is not a error message, it is the last word used by
the compiled program.
For your further information: my german ACT I manual is printed in sept.
1961 and the ACT V manual is printed 1964. My original paper tapes are
labeled 1965.
Best regards
Klemens
Klemens Krause
Universitaet Stuttgart / Inst. f. Softwaretechnologie
Breitwiesenstr. 20-22 / 70565 Stuttgart
Tel.: 0711/7816 341
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- Bob Supnk writes (Jan 2004)
I'm plodding along on an LGP-30/LGP-21 simulator. Your site, and the
others, have been very helpful. There was a lot more material than I
expected. I even found an archive of transcribed paper-tapes, although now
I can't figure out where it came from.
My goal is to get Blackjack running and then leave the rest to users.
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- Martin Olsiewski writes (Feb 2007)
I worked on the LGP 30 when I got out of the Marine Corps in Feb.1966
for one year. Control Data Corp. had purchased many of the "beasts" from
Librascope and was refurbishing the machines for resale for
approximately $10K. The mini computer was just beginning to appear (PDP
8, etal.) and pretty much ended what little future the LGP 30 had. I was
always proud to say I worked on a first generation computer.
I really didn't get too involved with software. This was my first real
job. I was a repair man for continuous wave radar on the Hawk missile
system while in the Marine Corps. Much of the work I did on the LGP 30
was stripping the cards and drum memory out of the frame, then cleaning
the carcass and trouble shooting. We typically replaced the bearings in
the blower and then began to reassemble the machine. The enclosure
panels (skins) were sent out for paint and every drum memory was
stripped of oxide and had new bearings installed. The drum had to have
less than .001 inch of run-out after the bearing change, if not they
were changed again until it met spec. Then the drum was painted with
oxide and cured. In the mean time the mainframe was put together and
tested with a place_holder drum memory without skins. After a while I
had developed some pretty thick skin on my fingers replacing tubes
during the testing and trouble shooting process. All the heads were then
mounted on the refurbished drum and set to some head/drum spacing, I
don't remember what it was, but it was close. The drum memory was then
mated with a frame and the testing and burn-in began. The acid test came
when we enclosed the frame with the newly painted skins. The temperature
rise on the inside of that beast was pretty significant, we some times
lost a drum when a head crashed and everything got reset to zero as far
as the drum was concerned. Most made it out the door to some lawyer or
doctors office.
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- Dave Bowles writes (April 2007) ;-))
Hello Ed,
I thought you might get a chuckle out of this. Sherman, set the wayback machine…
In 1967 I was 17 and I traded a CCTV camera and $150 for two LPG-30’s, a Flexiwriter, a
high speed paper tape reader and a high speed paper tape punch. I was nuts about computers
and could not believe my incredible good fortune to actually have my very own. I was told
the units had come from John’s Hopkins University - Applied Physics Lab in Maryland where
they had been used to calculate satellite orbit data until they were decommissioned.
Everything had allegedly been maintained by Royal McBee and had been recently reconditioned
before being put into storage for a few years before being sold as surplus.
I had no documentation or software for either of these machines and could not locate any.
A tantalizing cover sheet for a piece of software called SNOBOL was all I could find.
Unfortunately, the drum on one of the two LGP-30’s seized during my initial checkout.
It ripped itself from the mountings (which must have been loosened) and proceeded to screech
horribly and flail about tethered only by the head nest cables. The experience gave me a
totally different perspective on the enormous drum memory system called a “FastRand” that
I had seen at the University of MD’s computer center.
Anyway, undaunted, ignorant and determined, I got the remaining LPG-30 working using the
parts (mostly dead tubes) from the other and I learned quite a bit about computers and
programming in the process. Most fortunately, the Flexi and paper tape hardware worked
perfectly. I scrapped the dead unit and maintained the working one for about 4 years.
In the interim, I wrote a bootstrap loader, an assembler and an editor for it which made
it much easier to use and involved far less eyestrain from continually aligning the accumulator
trace with the printed graticle. I do not think the term ”Running Light Without OverByte“ had
been coined by a not-yet-existent Dr. Dobbs Journal at that time, but I definitely got the
concept.
I eventually traded the whole system to a physics student from the University of MD for $100
and a broken portable 1” Sony VCR and camera combo. Then, about 4 years after that in 1975,
I ran into an LPG-30 again. It was sitting cozily in the basement of a fellow electronics
entrepreneur that I was meeting for the first time. I could not believe my eyes. Here was
someone else with an LPG-30! How many of the darn things were there anyway? As it turned
out, this LPG-30 was indeed my old friend. He had received it free and clear when it was
discarded from the physics department at the UMD. Looking more closely, there was an unfamiliar
aluminum Bud box sitting on top of the drum. He told me that the drum had failed over time
since he acquired the LPG-30. On a lark, he had actually designed, layed out, taped up and
etched the PCB’s to construct a 2102 (1K x 1) based memory system replacement for the drum.
He then turned the darn thing on and showed me that it still worked. It had been 8 years
and there I was back squinting at the CRT O’Scope again and tweaking the knobs to align the
trace with the tick marks. Some things change, and some things don’t.
The last I heard, that LPG-30 had gone to its final rest.
Dave Bowles
Annapolis, MD
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An adventure
e-mail from Bill Seater - Nov 2011
My first experience with a LGP30 was when I decided to take a computer programming course at a
community college in Northern Michigan in the Fall of 1964. I wasn’t doing very well in
understanding programming (ACT III) until the very end of the course when suddenly, a light came on.
I re-enrolled in the same course the following Winter. This time I aced the course.
A year and a half later I was drafted into the U.S.Army and ended up at Ft. Belvoir, VA to be
trained in a non-computer related field. One day while walking by the post data processing center,
I decided to go in and hope for a miracle. The director said to me, “I don’t have anything here
for you but there’s a place down the street that’s looking for someone who knows anything at
all about a LGP30”. Two days later I was transferred to the U.S.Army Management School (USAMS).
My job was to punch a tape and feed data into a modeling program on the LGP30. Shortly after I
started I was to attend a two week programming course at Control Data in Rockville MD. On the
way up there the first day I was thinking, “It’ll be nice to get a refresher course in ACT III”.
But then I discovered that they were not teaching ACT III, they are teaching Machine language.
[ In the picture, the machine just to the right
of the LGP-30 is its High Speed Paper Tape Reader/Punch. ]
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The two weeks seemed to fly by. Back at USAMS there was a lot of down time. Mostly run the modeling
program once or twice a day. Lots of time to think about an application where I could apply my
newly acquired skills.
I noticed that one of the duties my office partner performed was to score (by hand) a 50 question
multiple choice test taken by the 52 students in each class at the school. What made this job
more difficult than usual was there was not just one correct answer and some answers were more
correct than others, and thus scored more points. Also some answers were so wrong that, if selected,
would deduct points. Additionally, he also did an analysis of each question (how many answered A,
how many answered B etc…). All together, it took about 3 days to complete, including typing a
report of the results.
So, in my spare time I began programming the LGP30 in machine language to score the test. Fortunately
I was able to exploit the architecture of the computer because there was always less than 63 values
in each category.
In the end I was able to cut that 3 day job down to 1 ½ hours, including punching the tape and
printing the results.
Bill Seater
Now living in Traverse City MI
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A weird blunder on Wikipedia - as of Dec 27, 2016
This web page was up and running before Wikipedia really got going.
see
An advantage of Wikipedia is that experts can pour info into it :-))
from Main_Page
- "the free encyclopedia that anyone can edit."
A disadvantage is that "experts" can do the same :-((
A current (Dec 27, 2016) statement in
https://en.wikipedia.org/wiki/LGP-30 is:
"It also had an integer multiply but,
because the accumulator had 32 bits while memory words had only 31 bits,
only even integers could be thus represented."
The above would be funny on "Saturday Night Live", but is weirdly incorrect on Wikipedia.
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Jürgen_Müller sent me an early version of his series of FPGA based LGP-30 clones.
More info is here.
Please excuse the "inch" scale in the photo. "Americans" insist on continuing to use
this measurement system of a long dead English king, which we fired, rather the handier
metric system used most other places ;-))
Now, in order to play with this, I have to remember how to think :-((
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Comment from Cory Heisterkamp < coryheisterkamp @ gmail . com >
Sun, Apr 15, 2018
In fact, it's snowing this very minute. So what better way to spend a little time
than to wrap up Jurgen's LittleGP-30 project. Electronically it was complete, but
finding printable-transparencies was a tad difficult until I remembered some
"official IBM" ones I had stashed away 20 years ago. Worked great! I had some scrap
aluminum angle out in the shop to make a base and used a mini-disc sander to get
the standoffs appropriately sized. I had the perfect vintage knob to use, but that
required a little drilling-out. Added some rubber feet....Perfection!
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- Dartmouth College Price - from Spring Ford - Dec 2019
-
From Stuart Olson - Wed 8/11/2021
I read with interest your history of the LGP-30.
I was an early user of the computer installed at the Ordnance Management Engineering Training Agency
(OMETA) on the Rock Island Arsenal, Illinois.
I quickly learned the machine language and the interpreter for solving many complex physics problems
for development of large caliber howitzer systems. Then we subsequently acquired a new programming language
called DICTATOR (I forgot what DICTATOR stands for). It was a massive roll of tape that took about a
half hour to load through the Flexowriter, but became faster with the new optical reader.
DICTATOR was a 3-address interpreter using automatic floating point math, making the LGP-30 easier
for engineering work, but much slower than machine language programs.
I'm surprised you didn't mention DICTATOR in your piece.
Thelen here:
Surprise to us all - searching for "LGP-30 DICTATOR", I found useful hits.
- I copied this from
- http://bitsavers.trailing-edge.com/pdf/royalPrecision/LGP-30/en/H1-124_Oct1959.pdf
- seemingly distributed by "LGP-30 Users' Organization-Pool"
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Thank you.
Stuart W. Olson, PhD
2340 Wassum Trail
Chuluota, FL 32766
407-365-6836
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Updated April 2022 - a photo added to Photo