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I > IBM  > 5120   


The 5120 integrated system was the last evolution of the 5100 and 5110 portable series, and the last 'heavy desktop' computer made by IBM.

The 5120 was an intermediate system between the IBM mainframes and the future 5150 PC. Actually, it was the first desktop Personal Computer made by IBM.

Basically, The 5120 technology remained the same as the 5100 model: same custom processor and same IBM typical hardware profile inspired by the mainframes technology.

The system featured a 9-inch monochrome moniteur (many 5100 users asked for a larger display) and two 8" floppy drives.

The system was sold with both APL and BASIC languages in ROM. APL allowed numerous business software written on IBM minicomputers to run on the 5120.


Bruce Franklin specifies:
After the IBM 5120, IBM manufactured another computer in Rochester based on the Intel 8088 chip that was called the DataMaster.
The computer's performance was poor compared to the 51XX computers, and IBM did not sell many of them.
Most people attribute the "IBM Personal Computer" as the first of what we know as PC's today, however IBM's model number for the PC introduced in 1981 was the IBM 5150. It was merely a new model of the 51XX line of computers and the second model to use an Intel processor.

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Worked on 5110s and 5120s in the NYC commercial printing industry. Wrote an entire job costing system, estimating syste, union payroll system, GL, AP, Billing and AR systems. This was in the 1980s. Had it running at many of the premier large print shops that were all over lower NYC in that period. One configuration had attached "toaster" 8 inch drives. The entire company ran by time slicing their departments. They went on for years until I wrote a conversion program and put them up on a 36 (in Basic). 64K was a thrill to run a full, multi-union, in-house payroll for 50 or so employees across 3 shifts.

Friday 16th February 2018
mark uihlein (United States)

I programmed a complete Property-Tax accounting system on one of these IBM 5120 computers, back in 1982... for City Hall in the town where I was living. The 5120 had 32K, no hard drive, just two 8-inch floppy disks, for programs and data. So: no real operating system either. It booted from ROM, and gave you a prompt in APL or BASIC.

As I recall, the style of BASIC was very limited/simplistic. For instance: no "FOR" looping, just use conditional branching. The "IF" statement only had syntax: "IF ABC $ X THEN 2500" where 2500 was a line number to GOTO when the IF-conditional was true. Even the 5120 Disk access was crude. IBM re-used old tape drivers, so the floppy disks would only understand FIXED length FILES, pre-allocated when created... so you needed to plan the Max size for a file in advance, and if that filled up, "too bad" you can''t extend file length... gotta re-build allocations, and copy to another 8" floppy.

However, despite computer''s limitations, I designed and coded a solid Tax accounting system that tracked property owner/address/value/zone for the whole town, calculated taxes, printed mailer statements, collected taxes, logged fees/fines, and allocated funds to appropriate city funds $ levees... which was running for as long as they kept the computer.

The IBM PC was brand new at the time, with more memory and a hard drive, and would have been a better choice$ but managers had already purchased the 5120, and stuck with it.
I guess one of the things I learned from that project is that the right skill for coding/design/efficiency/usability can make more difference than the computer it''s running on... and THAT remains true for system many years later.

Friday 31st March 2017
Joseph (Atlanta GA / USA)

Still have our IBM 5120 programed it back in 1980 as a 13 year old. It was my first experience with Basic programing. We also considered system 32 and 34 but my father settled on the 5120. I still like to turn on occasionally and pretend like it''s 1980 all over again. Also like the diagnostic switch on the monitor that lets you view the binary memory core. Have the displaywriter printer that came along with it. I seem to recall it costing about $13,000 or so. Looked at the Datamaster shortly after but we never took the leap.


Wednesday 29th October 2014
Kurt Zentmaier


NAME  5120
TYPE  Professional Computer
YEAR  1980
KEYBOARD  Full stroke 73 keys with numeric keypad
SPEED  Unknown
RAM  64 KB
ROM  64 KB
TEXT MODES  64 chars x 16 lines
COLORS  Monochrome
SOUND  Beeper
I/O PORTS  Parallel and Serial
BUILT IN MEDIA  2 x 8'' 1.2 MB floppy drives
POWER SUPPLY  Built in power supply unit
PRICE  $13500

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