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I > IBM  > PC - Model 5150   

PC - Model 5150

The computer which caused the death of CP/M computers.

In the early part of 1980, IBM decided to create a microcomputer (up to this date, IBM produced only mini and mainframes). They didn't really know that they wanted and they didn't think for one second that producing microcomputer was a profitable business (who would have thought!)!
After hesitation between the Intel 8086 (16 bit) and the Motorola MC68000, they decided to use the Intel 8088 (8 - 16 bit) processor, as the two other ones were considered too powerful! Then they asked to Digital Research (the creators of CP/M) to create an operating system for their new computer, as DR was not very interested, they then asked a small company (famous for its BASIC Programming Language) to write the operating system: Microsoft.
Microsoft wasn't capable of doing it, Bill Gates bought the rights to a small, hacked OS written by a small company called Seattle Computer Products: QDOS (which reportedly stood for "Quick and Dirty Operating System", which itself bears a striking resemblance to CP/M) which became PC-DOS and then later MS-DOS!
In fact, when it was launched, three operating systems could run on the IBM-PC: PC-DOS, CPM-86, but also the UCSD D-PASCAL system.

The original IBM PC wasn't very powerful (and was certainly less powerful than lot of 8 bit computers at the time). The very first PC’s had only 16 KB RAM and no floppy disk units, they used cassettes to load & store programs (notice that the commands to handle the cassette drives were present in the operating system all the way up to MS-DOS 5!). In fact, units could also be purchased from IBM with drives and more RAM. Only the lowest cost version had no drives included (this is exactly how Apple and the other manufacturers did it as well).

The model 5150 was actually a success due to name and fame of IBM, high quality construction (especially the keyboard and monitor), great expandability and IBM's decision to publish complete technical specs. The IBM PC Technical manual included circuit diagrams and the full source code for the BIOS! The PC 5150 became a standard and IBM ran the business computer market up to the end of the 80's.

Now, we can consider that about 90% of the microcomputers are PC compatibles and run under MS-DOS or Windows (At the beginning, Windows was just a graphic interface for MS-DOS, but that’s another story).

Although the IBM PC XT was launched in 1983, IBM continued production of both units, in various configurations, for several years. The model types were followed by a xx version number, i.e. 5150-xx, where the xx represented the included options (amount of RAM, single or dual floppy disk drive, etc.).

Jeffrey H. Ingber reports that when these computers (PC and XT) were initially sold, they were built-to-order computers (sounds like Gateway or Dell, doesn’t it?). Retail outlets would carry the factory products, which consisted of a boxed computer with basic components such as the motherboard, power supply, floppies & floppy drives, etc. There was no official base model configurations for the PC and XT.
Customers had a choice of RAM, display, serial ports, etc. that they could have installed on-site before the computer went home.
One could not purchase a "new" PC/XT and run it out of the box becuase it was incomplete without additional configuration.

The PC was available with either CGA or MDA (on an MPA card). The CGA adapter actually has an RCA composite output to hook it up to your TV if you did not want the CGA monitor. The output quality was PERFECT!

Another notable great feature of the PC line was the expansion base: it added additional (I think it was eight) 8-bit slots in an external enclosure.

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Email is

Tuesday 22nd September 2020
Jay (Washington State USA)

I am looking for one of these at a cheap price, I will pay up to 100$ including shipping if I have to pay for it

Tuesday 22nd September 2020
Jay (Washington State USA)

Hey, I´m into a project.
Looking for an old IBM 515O STYLED PC AND SCREEN.
Don´t need to be working, just need the enclosures: PC and the screen ones.
(The PC elcossures should have the floppy readers)

Saturday 9th November 2013
Rogelio (México)


NAME  PC - Model 5150
TYPE  Professional Computer
YEAR  1981
BUILT IN LANGUAGE  IBM BASIC (Special Microsoft BASIC-80 version in ROM)
KEYBOARD  Full stroke 'clicky' 83 keys with 10 function keys and numeric keypad
CPU  Intel 8088
SPEED  4.77 MHz
CO-PROCESSOR  Optional 8087 math coprocessor
RAM  64 KB (The very first ones had only 16 KB), 256 KB max. (then later 640 KB max.)
ROM  64 KB
TEXT MODES  40 or 80 char x 25 lines
GRAPHIC MODES  Optional CGA graphic modes : 320 x 200 / 640 x 200
COLORS  Monochrome / 4 among 8 in 320 x 200 CGA mode
SOUND  Tone Generator - built-in speaker
SIZE / WEIGHT  50.8 (W) x 40.6 (D) x 14 (H) cm
I/O PORTS  Five internal 8 bit ISA slots, monitor, Centronics, cassette (!),
BUILT IN MEDIA  One or two 160 KB 5.25'' disk-drives
OS  MS-DOS, CP/M-86, USCD Pascal
POWER SUPPLY  Built-in 63.5W switching power supply unit
PERIPHERALS  5 expansion slots, 5, 10, 20 MB hard discs
PRICE  Ł1736 (1 FD, monochrome monitor, U.K., 1983)

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