Model 80 PS/2 Page

Created on: 28/02/1999
Last Update: 14/05/2000
Restored 03/02/2012 for historic purposes.

  This page was made very quickly and will be updated sortly.  
  In the future this site will contain much more info about PS/2's especially Model 80's (8580).  
PS/2 INFO MY PS/2 Connect a PC FDD to a PS/2 Links E-mail


Information About the Model 80
The following information was obtained from IBM Canada.

IBM Personal System/2 Model 80


  IBM PS/2 Model 8580-
  041 071 111 121 321 A21 A31
Microprocessor Intel 80386 DX 32bit
Clock speed 16Mhz 20Mhz 25Mhz
Display VGA, 320x200 @ 256 colours, 640x480 @ 16 colours
16 bit slots 5 slots 4 slots
32 bit slots 3 slots 4 slots
RAM 1Mb 2Mb 4Mb
RAM Type DRAM 80ns parity checked (2 sockets)
ROM 128Kb
L1 Cache 0Kb 64Kb
Power Supply 225W 242W
HDD Capacity 44Mb 70Mb 115Mb 120Mb 120Mb 320Mb
HDD Access time 40ms 30ms 28ms 23ms 23ms 12.5ms
HDD Interface ST-506 ESDI SCSI
FDD 1.44Mb FDD
PORTS PS/2 keyboard, PS/2 mouse, serial, parallel, VGA
Keyboard 101 key enhanced
Weight 23.6 Kg (52 lbs) (8580-041)
Height 597mm
Width 166mm
Depth 483mm
Drive Bays 4 3.5" half-height (2 accessable), 1 5.25" full height (or 2 3.5" HH)

Other Model 80's not listed
081, 161, 311, A16, M81, M16
Mxx - same as Axx but with 20Mhz CPU

Note: The above information is the original parts for each model.
Each model can be upgraded (Max memory 16Mb RAM)

My PS/2

I have a Model 8580-111 with the following

IBM 16Mb RAM - 6Mb on system board, two expansion cards one with 8Mb and the other with 2Mb.
IBM XGA-2 Display Adapter - 1Mb Video memory.
IBM Dual Async Adapter - Two serial ports (three including the one on the system board)
3Com 3C529 Ethernet Adapter - 10Base-T, RJ45 Connector.
Intel EtherExpress 16 - 10Base-T, RJ45 Connector.
IBM SCSI Controller
- DEC RZ26L 1.0 GB
1.44Mb PC FDD - for information on how to do this look below

I am running Slackware 7 on it at the moment with Kernel 2.2.13
It is used as a router box for my internal network, it is running the following services:

Just shows what you can do with these old beasts!

Uptime since i got a cable modem is only 5 days on 14th May 2000
Thats when i upgraded from 115MB ESDI to 1GB SCSI
and to Kernel 2.2.13

I also have the following which are not being used at present. But will be when I get more PS/2's going.
(I like bringing these old things back to life)

IBM ESDI Adapter
- IBM 115Mb ESDI HDD - Original 5.25" Full height - now thats what I call a hard drive!
Arco IDE Adapter
Alliance Technology TapeDrive Adapater
3Com 3C523 - 10Base-T
HP Scanjet Adapter - Can also use as additional printer port
IBM PS/2 Model 8580-111 - dead FDD's
And a heap of cards i have not checked yet!

How to connect a PC FDD to your PS/2 Model 80
(may work on other models as well)

The Problem
The probelm was and is PS/2 Model 80 FDD's, the general problem is that they are very noisy, slow and collect a lot of dust.
But they are not the main problems. The main problem (in my experience) is that they die. Quite often in fact.

And when they die, well you have to buy another one. But the replacement is probably as old as the one that died and will die soon
to. So what can we do?

The Solution
The solution is to hook up a normal PC FDD to your PS/2. But this can present some problems of its own as we talk about later.
It may seem that the PS/2 FDD interface is completely different from the PC FDD interface. But don't be fooled by the large connector on the PS/2. From pin 1 to pin 34 all pinouts are almost identical, and the extra 6 pins on the PS/2 are for the power.

The Pinouts
I have included the pinouts of both interfaces. The PS/2 pinout came from the PS/2 FAQ and corrected by Peter Wendt, and the PC pinout came from an electronics store referece sheet.

PS/2 40pin 1.44Mb FDD pinout for old models (50/60, 55/65, 70/80 and P70/P75)

PS/2 40pin   PC 34pin
1 2nd drive 2 high density select   1 GND 2 high density select
3 reserved 4 reserved   3 GND 4 in use
5 GND 6 Drive Select   5 GND 6 drive select 3
7 GND 8 index   7 GND 8 index
9 GND 10 Drive Select   9 GND 10 drive select 0
11 GND 12 Drive Select   11 GND 12 drive select 1
13 GND 14 Drive Select   13 GND 14 drive select 2
15 GND 16 motor enable   15 GND 16 motot on
17 GND 18 direction in   17 GND 18 direction select
19 GND 20 step   19 GND 20 step
21 GND 22 write data   21 GND 22 write data
23 GND 24 write enable   23 GND 24 write gate
25 GND 26 track 0   25 GND 26 track 00
27 GND 28 write protect   27 GND 28 write protect
29 GND 30 read data   29 GND 30 read data
31 GND 32 head 1 select   31 GND 32 Head 0 Select
33 GND 34 diskette change   33 GND 34 ready
35 GND 36 GND          
37 GND 38 +5v          
39 GND 40 +12v          

The PS/2 FDD controller is a little different to the PC controllers. The IBM PS/2 FDD is "non media-sensing".
It uses a BIOS routine to blind-read the first sector of a floppy at Sect. 0 / Head 0 / Track 0 and uses the "media descriptor byte"
to set the controller according to the disk format (360 / 720K or 1.44MB).

Normal FDDs do it other way round: the pin 2 is "Density Select" - driven low for 1.44MB by the right-hand switch on the FDD ...
which is not present (or not functional) on the old PS/2 FDDs. This switch sets the controller to the according mode - a reason why
you can format 720K DD floppies to 1.44MB on PS/2 without drilling a hole into the floppy (media hole - right side of the floppy)
and "downformatting" 1.44MBs to 720KB without covering the media hole with some adhesive tape. It is simply not used on the older

But read / write /format of 720KB disks may not be possible because of this ( I have not tested it yet ).

The PS/2 controller is CMOS, so if you have a floppy disk drive that supports CMOS then this should work.
Thanks to Peter for providing this info.

So what does all this mean?
Well this is good news for people with PS/2 Model 80 FDD's that seem to keep dying.

My Experience
I managed to successfully attach a normal PC Floppy to my Model 80 with no re-wireing!
According to the digram if you plug a PC FDD cable into the right-most portion of the FDD interface
and connect the FDD up to the power supply, the disk drive should funtion with no problems (in my theory).

So I plugged a 34pin connector into the 40pin socket on the system board, matching pin 1 together.
Then I plugged a power connector between the power supply and the FDD. I booted up and the disk
drive light came on when it was suppose to. Good so far.

But when it came to booting the RefDisk or any boot disk it wouldn't work. It just loads IBM BASIC.
No good!!!!

BUT! I started to fiddle with the jumpers on the back of the FDD

I changed the FDD's logic setting by removing the jumper( it was labled TTL/CMOS). I plugged the FDD in, turned the computer on
with the RefDisk in the FDD, and after a while I saw that BIG BLUE screen I have been waiting so long to see.
Harray!!, I couldn't believe that it worked.

It runs very well, not as noisy as the PS/2 FDD's and probably a bit faster too. Those of you who want to run
linux on your Model 80 but can't load the root disk because of the slow FDD, well good news, with a normal
PC FDD there is no problem at all. I installed Linux quit easily.

I hope this helps others that have gone though hell with Model 80 FDD's (Maybe other models as well).


I have been running my PS/2 Model 80 with the PC FDD for over a year now... and its still running excelent!

What to do.
If you try this and blow up the FDD controller on the system
board or your FDD (Very unlikely), don't blame me. I took a risk trying this
out on my PS/2. And if you want to do the same, do it. But
if you are worried about the PS/2 system board don't do it!

What you need:

Connect everything up, power connected between FDD and spare socket on power supply. I there is no
spare socket, buy a 4pin power splitter. Connect the ribbon cable to the FDD and then connect it to the
FDD interface on the system board as shown in the diagram below, leaving 6 pins unconected (the power
for PS/2 FDD). (Remember the red wire is pin 1)

Dont forget to change the logic setting on the FDD!

Mounting it
The way I mounted mine was in the 5.25" accesable bay. I used a 5.25" to 3.5" bay converter (as shown in figure).
I made up two thin wooden blocks so the converter would slide into the HDD support structure.

Here is a diagram of what my PS/2 lookes like with the PC FDD.

The only thing I am missing for this is the cover plate which had a HH 5.25" hole in it, to cover the gaps.


Description URL  
IBM Canada  
The PS/2 Page  
Microchannel Linux  
MCA-Adapter Pictures Collection  



If you live in Melbourne Australia and want to throw away your PS/2 Model 80, or any PS/2 parts email me and I might
take it off your hands free of charge.. :-)

If you have any questions. Success stories or failures. with Model 80 PC FDD's Please email me.