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I > IBM  > PS/2 Model 25   


IBM
PS/2 Model 25

IBM was struggling in 1986 against Apple's Macintosh series, so IBM set out to create something that would defeat the Macintosh. IBM came up with a all-in-one similar to the Macintosh. However, the Model 25 & 30 were the low-end (budget) models of the PS/2 range.

The PS/2 Model 25 became quite popular with businesses, but never made it strong with the home market.

The PS/2 Model 25 & 30 were the only system using the MCGA (Multicolor Graphics Adapter) standard. They came with this video features built-in. MCGA offered all text and graphic modes of the CGA standard plus 640x480 monochrome and 320x200, 256 colors (out of a palette of 262,144). It announced the future VGA standard which will become much more popular.

Model 25 & 30 were also the only PS/2 systems using an 8-bit ISA bus (like PC ATs), as opposed to other PS/2 models which used a 16 or 32 bit MCA bus.

Thanks to Alex Rushing for info and picture

Further information from Brandon:
The model 25 came in two models, a monochrome model, and a color model. The monochrome model usually is called "Type 001", the color one being "Type 004".. There never was a type 002, or 003.
The motherboard for the color and black and white models are exactly the same, minus some revisions on the later years. They were always surface mounted though (most of the chips anyway).
They are a tough machine, though when you install one in a new room, it NEEDS to let sit in the room for a couple hours, otherwise the power supply/motherboard will die.
While the floppy drives were 720KB, they "could" use 1.44MB drives, as long as the interface was the same.
They contain TWO BIOS's in them. One called the CBIOS, and the other called the ABIOS.. CBIOS is "Compatible BIOS", and is used for DOS or Windows 3.0 and under... ABIOS, or "Advanced BIOS", is used when it runs OS/2.. OS/2 is the native OS to this unit. They also had an option for a hard drive.


We need more info about this computer ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful.

 

Ah, nostalgia. This was the very first computer I ever learned on! When I was in Elementary School, we had a computer lab that were all these IBM machines. Granted, by this time, they were getting a little long in the tooth (It was the late 1990''s), but nonetheless, they were my first foray into Computers. I even have a picture my teacher took in my 2nd grade class of me by the computers.

I still remember the typing program we used, as well as the educational game where you would solve math problems to help the characters build a rocket ship, have it take off, and then land again.
Can''t remember the name of the game though. I wonder if the school district still has a few in a forgotten corner of a warehouse somewhere?

          
Wednesday 4th September 2019
Anthony B.  (Missouri, USA)

There were a lot of field returns for these 2 mother boards. I was the bench tech that repaired them at north american philips in Tampa. The via''s in the boards were horrible. The most common cause of a mother board failure was a thru hole connection between layers. These would usually read about 6 ohms with a meter, but the signals would not pass. there was another common failure to of the post i think the code was 1165, it was the RTC. a port 80 card was very handy for trouble shooting

          
Tuesday 23rd October 2018
paul (usa)

Can anyone out there tell me what ic''s I need to get to do I ram upgrade for my 8086 model 25. I have the parity ram in the slots but I''m missing the 6 chips that are located near the bios and rom

          
Monday 5th June 2017
Kris

 

NAME  PS/2 Model 25
MANUFACTURER  IBM
TYPE  Professional Computer
ORIGIN  U.S.A.
YEAR  august 1987
END OF PRODUCTION  Unknown
KEYBOARD  Full stroke keyboard, PS/2 type
CPU  Intel 8086
SPEED  8 MHz
CO-PROCESSOR  optional Intel 8087 (math co-processor)
RAM  512 KB, upgradable to 640 KB
VRAM  Unknown
ROM  Unknown
TEXT MODES  Unknown
GRAPHIC MODES  MCGA graphics : 640 x 480 in monochrome, 320 x 200 in 256 colours
COLORS  262 144 colours palette
SOUND  Internal PC buzzer
SIZE / WEIGHT  Unknown
I/O PORTS  Parallel port, 9pin serial port, 2 x ps/2 ports, 2 x internal expansion slots (8-bit)
BUILT IN MEDIA  one or two 3.5'' floppy drives (720 KB each)
OS  OS/2, DOS
POWER SUPPLY  Built-in power supply
PRICE  Unknown




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