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IBM 5100

Manufacturer IBM
Identification,ID 5110
Date of first manufacture-
Number produced -
Estimated price or cost-
location in museum -
donor -

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IBM 5110

IBM 5100 Personal Portable Computer, 1975

The IBM 5100 Portable Computer was IBM's first attempt to build a personal computer. It weighed 50 pounds, had a built-in tape drive, a small CRT and the ability to run programs in either BASIC or APL. The monitor could diisplay 16 lines of 64 characters each, the memory couuld be expanded to 64K and the tape drive used a 1/4 inch tape cartridge which held 200 K of data. With a 32 K RAM upgrade, this machine sold for $14,275.

This sample is the 5110.


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From LaFarr Stuart
I have "IBM 5110/5120 Computing Systems APL Reference Manual" Third Edition (July 1980). The copyright lists 1977, 1978, 1980. So I expect that the 5100 came out in 1977.

I just noted that on page 45 the description of File Type 06 says; "APL continued file-5100 only" This more or less confirms what I remembered: The first was a 5100 then latter there was a 5110 and finally a 5120. Incidentally, and this is from memory, when IBM released the first 8088 based PC it was officially the IBM 5150.

I suspect that the comment you got about the photo being a 5110 is correct. He seems positive about it. And I think if the 5110 had disk instead of the tape it was in an external box. The photo appears to have the tape slot simply covered, which was not an option on the 5100.

APL was an extra cost option BASIC was standard. (IBM did some very dumb things, or APL would have been the major language today instead of C, obviously my opinion; but it is correct!) The photo unit does not have APL because: above right side of the keyboard there is room for 4 rocker switches (It looks like 5 but the left position was never used.) The left switch (which is on the photo) was the "REVERSE DISPLAY" this determines whether the display is light characters on a dark background or the opposite. The next switch is the BASIC/APL switch "Only dual-language machines have this switch." The third switch is a RESTART, and the fourth is DISPLAY REGISTERS/NORMAL for use by service representative's.

"The 5120 uses the 5110 Model 3 computer." It has two built-in diskette drives and a larger screen.

The IBM 5100 actually emulated the IBM 360 and ran the 360/APL interpreter. IBM was paranoid and afraid somebody might run 360 programs on the 5100. Good engineering, but stupid marketing. But then what else is new? As far as I know the last time IBM successfully marketed any software it was FORTRAN, for the 704. But dam, their machines are reliable workhorses. (With parity, at least initially!)

From Hans B Pufal August 10, 2003
I was confused about these two machine designations. I am still confused but a soemwhat less.
According to the IBM archives ( ), the 5100 was announced in Sep 1975 avalaible in 4 models (4 memory sizes and 3 language choices). It was aimed at scientific and engineering applications i.e number crunching. It seems from the photos on the IBM site that the 5100 had an off-wite bezel.
Again according to the IBM site the 5110 was released in January 1978. The pictures all show a black bezel. There were two models the model 1 with a tape drive and the model 2 without, the model 2 could have disk storage attached. The 5110 was aimed at general business users.
The two were clearly distinguished by IBM but nothing is said about the exact technial differences. Was it just a marketing exercise? Was it just added software or was there in fact a physical difference?
Your photo is presumably a 5110 model 2. We have a 5110 model 1 here at ACONIT.
As an aside, our 5110 did not have the language switch, it was an APL only machine. During an examination of the interior found a pair of unconnected wires just behind the blank where the language switch would be. The simple act of putting a switch on those wires converted our APL only machine into an APL/BASIC machine. It would be interesting to know if APL was built in to the BASIC only configurations.

Best regards,

-- Hans B Pufal

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Updated August 11, 2003