IBM 5100

IBM 5100 Computer

The IBM 5100 Portable Computer was a portable computer initially sold towards the end of 1975. It was IBM’s more advanced version of their earlier Special Computer APL Machine Portable. It is also recognized as the predecessor to the more popular IBM PC which would be released in 1981. The IBM 5100 was very much ahead of other similar machines at the time, like hobbyist microcomputers MITS Altair 8800, and the IMSAI 8080, and was priced much higher as well. While microcomputers of the time could be bought as DIY kits for under $500, the IBM 5100 ranged from roughly $9,000 to $20,000 depending on the options. Because of this price, and the advanced technology, the IBM 5100 was marketed more towards engineers, analysts, statisticians, and other problem solvers and big businesses.

The IBM 5100 was marketed as the world’s premiere portable computer. It weighed a little over 50 lbs, and unlike many microcomputers at the time, it came fully assembled with integrated features like a keyboard and CRT display, as well as system software. The entire unit could fit into an optional case for the machine, which would allow owners to transport their computer easily from one place to another. Although out of the general computer and hobbyist enthusiast’s budget at the time, it received rave reviews from electronic magazines of the time. People marveled at how much information could be stored, and features integrated into what at the time was a very small functional computer.

IBM 5100 Case


The IBM 5100 used a board level microprocessor known as PALM (Put All Logic in Microcode). Initial speed was roughly 2 MHz. Memory varied depending on the features the buyer chose but it ranged from 16KB to 64KB RAM, and 32KB to 64KB ROM. Storage was provided by a 1/4 inch cartridge tape drive using DC300 cartridges to store 204 K bytes. It used a 16-bit address bus. It came with an internal CRT which displayed 16 lines of 64 characters, and was equipped with a connector that an external video monitor could be attached to if the owner bought a separate external monitor. It was equipped with an integrated keyboard and could be purchased with APL, BASIC, or both.


The IBM 5100 was one of the first widely marketed personal computers, and the most advanced and innovative one of its time. No other micro or personal computers at the time even came close to its integrated features and technology, and it is widely considered the first all in one assembled portable computer system of its kind in the history of computers. Its high price tag made it unsuccessful as far as sales went, but it would eventually lead to the 1981 IBM PC, and all the more well known personal computers that would follow.

Interesting Facts

During 2000-2001, a bulletin board poster who went by the name John Titor caused a sensation around the internet and on popular radio shows like Coast To Coast AM by claiming to be a time traveler from the year 2036. Titor claimed that he had been sent back in time to find an IBM 5100.

IBM 5100 Inside
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