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More PS/2 trouble

S

snq

Experienced Member
Joined
Mar 29, 2009
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164
Location
Sweden, way up north
It seems I really screwed it up now...

As you may have read in my other thread I've been having a bit of trouble getting the diskdrive to work on my PS/2 50 (8550).. Which was not the end of the world, it has MS-DOS installed so I was about to get ready to use interlnk/intersvr to transfer files to it.
Before doing so, I wanted to check what was on the new harddrive I bought for it, all of 120 MB and who knows what kind of exciting stuff might be on it.
So I removed the old one and plugged in the new one.. Switched it on, and now I get the ROM basic instead of booting from the harddrive. I plugged the old drive back in, same thing. So now I'm reduced from dos to basic ;)

So, how am I going to solve this one? I assume I really need to get a hold of a working diskdrive now so I can use the reference disk?
Is there any other way?
 
Really check both ends of the hard drive connection cable. Sounds like a loose connection to me. You could even pull the cable connector totally off on the motherboard side, and push it back on. I bet it came about 1/2 out, where half the connector is still hanging on and the other half is connected to air. It can be sitting there, and looks ok but it isn't.
 
Thanks for the tip, but it doesn't have any cables. There's a riser card that sticks into the mainboard, and the harddisk plugs straight into the riser card. Same with the diskdrives.
I removed all of it anyway, and plugged it back in. I can hear the harddisk spin up and seek for a bit, but I still only get to the ROM basic.

I should add that the battery is bad as well and I'm pretty sure that has something to do with this, I get a 161 and 163 error at startup.
161 - Low CMOS battery
163 - Invalid Time and/or date
 
Ok, looks like it's time to fix the cmos battery. Those 2 errors are extremely common and if I was betting, I would bet that the machine would work perfectly by just pressing F1 twice. But it seems clear that it has lost the drive type info. So, it can't see the hard drive, figures there isn't one, and drops into basic. Almost every computer made by IBM around then did that exact thing, no hard drive, drop into basic.

So........
Your idea about needing a reference disk is correct. It will be required now, no matter what. You can run the reference diskette with the current cmos battery. Likely, every time you turn it off, you will get to repeat the reference disk thing when you turn it on. Or, fix the cmos battery, do the reference disk thing once and voila.

End of my story here. I don't know what kind of floppy you have. And how it gets the power. Other people have grabbed a normal floppy drive from another machine and just let it hang there to get the machine booted up. I don't know if that is possible because of lack of knowledge with the current setup.
 
Yes, it would seem that way. I want to get hold of a working diskdrive first though, because without that I'm not going to get anywhere at the moment.
If I can't find a replacement battery I'll just hook up a couple of AAs, that should work, but a bit too late for that now.

The diskdrive has partnumber 90X6766, it's not the original for this machine but it has the correct connector. The connector looks like this and I haven't been able to find any adapters to connect a regular FDD. If anyone knows if that can be done at all, I'm all ears!
ibm90x6766-3.jpg
 
Re: adapter cable.. I found some interesting information..

The 40 pin "cartridge-type" pinout:
http://ohlandl.ipv7.net/floppy/Floppy_Pinouts.html

And regular 34 pin pinout:
http://pinouts.ru/Storage/InternalDisk_pinout.shtml

They look pretty similar to me.. With the exception of power being included in the 40-pin. (Not sure why it has 40 pins anyway, 20 of them are ground ;))

I think I may have to just give it a try.. At the moment I'm not getting anywhere at all, and these diskdrives aren't exactly free. And I do have a big pile of working 34 pin drives..
Has anyone tried this before?
 
I don't see any 3 or 4 pin connector for the power. Meaning, the power is likely on 2 of those edge connector strips (well, 4 counting the return grounds on the other side). Plug a normal diskette drive into the female edge connector on the riser and ZAPPPPP would be the likely result. Normal floppiy drives don't expect any of the 34 pins to be used for power. I do have but not for sale, a male edge connector with a male 34 pin on the other side, very short adapter.
 
The power would come from pin 36/38/40 on the 40-pin, it has ground, +5V and +12V so it's the same as the "modern" 4 pin FDD power connector.
With similar I meant that they seem to have the same functions for the pins, not necessarily in the same position though. The only difference I see between the pins is that the 34 pin has a Drive Select A/B and Motor Enable A/B whereas the 40 pin only has one Drive Select and Motor Enable.

Would it be possible to get a picture of the adapter you have?

I found some more information here:
http://www.tavi.co.uk/ps2pages/fdadapt.html
 
I fabricated an adapter cable last night, but it's not working.. The light on the drive never comes on, and I get a 601 error. At least I didn't blow anything up, the old drive still works somewhat, except it won't read any disks...

I get 5V and 12V in the right places, but have no means of testing any of the other stuff. I did check for shorts between the other pins but nothing there.
I only connected a couple of the ground wires, they are all connected to the same ground both on the 40 pin connector and on the drive, so I don't think it's necessary to connect all of them?

Anyway, my pin conversion goes like this. All odd pins are ground on both, with the exception of pin 3 on the 40 pin side, which is reserved.
Code: 
40pin   34pin   Desc        
2       2       Density Select
4       x       Reserved
6       x       Reserved
8       8       Index
10      x       Reserved
12      14      Drive Select (A)
14      x       Reserved
16      10      Motor Enable (A)
18      18      Direction In
20      20      Step
22      22      Write Data
24      24      Write Enable
26      26      Track 0
28      28      Write Protect
30      30      Read Data
32      32      Head 1 Select
34      34      Disk Change
36      x       Ground (I'm using ground from a different place though)
38      PWR     +5V 
40      PWR     +12V

Some pics of my adapter.. Nevermind my soldering, it's been a while ;)


Even pins, 2 left, 40 right.


Odd pins, 1 right, 39 left.


Any ideas what I'm doing wrong? In theory it all looked like it'd work perfectly ;)
 
Last edited:
It really is way too early here for all this kind of stuff!!

Ok, first, make sure the normal floppy drive you are using is jumpered as DRIVE B!! Super important.

Next, as you are attempting to use a regular floppy drive, the IBM drive pinouts are misleading.

Need to do :

controller pin 10 to drive pin 16 motor a

controller pin 14 to drive pin 12 drive a

This is the famous "flip" in the A/B cable you always see.

It is obvious that the IBM floppy drives do the opposite, which is they grab the drive B signal and use it as if it was drive A.

And pictures of my stuff wouldn't have helped. All my adapters are for 34 connector type applications.

So, move 2 wires on your adapter, make sure about the drive B jumper on the drive (almost always already jumpered this way) and VOILA.
 
Ah, right. Your adapter is like the one described here then?
http://www.tavi.co.uk/ps2pages/fdadapt.html
Misleading indeed.

I can't find any jumpers on any of the drives I have here (checked 4 of them) so I will assume they are configured as drive B, if I understand it correctly it must have a terminating restistor.

I'm a bit confused about this A/B stuff now.. You're saying I need to switch from using the Motor A/Drive A to Motor B/Drive B because IBMs pins are misleading?
I'll give it a try, and we'll see what happens :)
 
It works :D
Thanks a million, Chuck! You just saved a PS/2 from being parted out ;)

I haven't gotten it to boot from a 1.44 disk yet, but 720k works fine. It could just be my disks, I'll keep trying.

Photographic evidence!

 
Yahooooo! Jumping around here too! 8 am is really too early for this kind of stuff. What you did is basically do the twist with some solder. If you had a female to male 34 pin converter cable, you could have used that plus a normal a/b floppy cable. I don't have a female to male 34 pin cable and I doubt you had one either. So, we used some solder instead.
 
You often hear "Oh, he's so smart. I will never learn all this stuff."

Well, I never knew about the "flip" or any of this floppy stuff until very recently. In my battle to get my Northstar Horizon to boot, I had to learn. So, I ain't so smart. I had to learn the stuff just like everyone else.
 
Yea, nobody knows this stuff from birth, everyone has to learn sometime :) I would never have thought of this myself so I'm glad you had the answer!

As for 1.44 disks, it's actually refusing to read any of them at all. The disks I'm trying with are 3M DS HD, never used but they have been on the shelf for probably at least 5 years.
When I replace the 720k bootdisk with a 1.44 after booting and try to get a dir listing, it just seems to hang forever with the drive led being on constantly.
Any idea what's going on? I'm wondering if it could possibly be solved by shorting the Density Select pin in some way?
 
You could run a wire from pin 12 to pin 2 on the male 40 pin connector that plugs into the riser. Then when the drive is select, so too will be high density. Of course, 720K floppies would likely not work.

Time for a switch on this new jumper or if you are really lazy, just solder a piece of wire to each pad and short them together when you want 1.44?

Edit: hmm, that's not such a great plan. Another would be to unsolder the wire from pin 2 and short it again pin 12 when you want high density. The first plan is bad because it leaves the original pin 2 in the circuit.
 
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