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IBM 5162 BIOS dated 1989-04-28

mrmanse

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Yes, you read correctly, 1989.

I recently purchased an IBM 5162 on Ebay, which not only came with 2 working Seagate ST-225s and a CPU running at 8 MHz, it also has a motherboard ROM reporting BIOS date 1989-04-28. I was told that it is a genuine IBM ROM by IBM France, and I did test that both the diagnostics diskette and the cassette basic works. Seems unlikely that a clone BIOS would have IBM cassette Basic. Compared to the standard 1986 ROM there are hundreds of differences, but the files aren’t completely different either, some huge chunks are the same.
I’d like these files to be offered to other enthusiasts, and possibly published on the absolutely great site minuszerodegrees. I understand that the keeper of that site is active in this forum.

/M
 

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per

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Thanks for sharing these!

This is very interesting stuff. I would be interested in seeing pictures of these ROMs, in particular getting to know the identification numbers. The code is labeled 78X7462, the same as the 1986 BIOS, but if the ROMs has proper IBM product codes different than the original 1986 version then this might most likely be an official upgrade. For reference, the 1986 version has ROM chips labeled 78X7460 and 78X7461. If it's in EPROMs, then it's a custom mod and not mass-manufactured. The source-code was available in the tech-ref, so making a patched version should not be too difficult for anyone to do.
 

modem7

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I understand that the keeper of that site is active in this forum.
That is me.

Interesting. My opinion is that some research needs to go into this. I mean, it could be that these chips have been transplanted from some other IBM machine.

The 5162 was released in 1986. According to accounts that I have read, it sold poorly (at least well below expectations). Accordingly, it does not make sense to me that three years after release, IBM would go through the process of developing a new BIOS for it. To what end?

I went looking to see when the IBM stopped shipping the 5162, but I could not (quickly) find that date. If that date preceeds 04/28/89, then I would see that as evidence that the 04/28/89 BIOS is not native to the 5162.

I am certainly not in a rush to indicate that the 04/28/89 is IBM's second BIOS for the 5162. More research is required.

Please provide a photo of the ROM set.
 

mrmanse

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Hi!

Yes, you are both most likely right that it can't be an official BIOS release since it isn't mentioned anywhere, but the person I bought the computer from claimed it to be made my IBM France nonetheless. Perhaps some beta version never released, is my best guess.

As you both suspected the BIOS is programmed into UV-erasable EPROMS (interestingly they are from 1988). The covers are made by some modern label printer, probably printed by the previous owner, and when I asked him about it he told me that the BIOS was already in the computer when he got it. So he checked the ROMs and left them untouched, i suppose. Here are some pictures, but I really think we should invite the previous owner of my computer to this thread, he knows much more about the origin of the computer. I'll email him.

IMG_0030_1.jpgIMG_0034_1.jpg
 

modem7

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Yes, you are both most likely right that it can't be an official BIOS release since it isn't mentioned anywhere,
This could be as simple as someone modifying the existing BIOS to achieve things like:
* adding more hard drive types;
* altering the bit of code that halts the POST if someone has put in a faster main crystal;
* stabilising code that was found to be unstable at 8 MHz.

Obviously, only someone analysing the code is going to work out what exactly was changed.

... but the person I bought the computer from claimed it to be made my IBM France nonetheless.
For the PC product line, I would have thought that all development work would have been done in the US, with international IBM offices involved in either production and/or distribution. There are forum members here who worked for IBM. Maybe they have some knowledge of that subject.

Perhaps some beta version never released, is my best guess.
That will be very difficult to prove.

It may be easier to disprove if we can find when IBM stopped shipping the 5162. I expect that at least one IT magazine of the time would have made mention.
 

mrmanse

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I can confirm that one of the additions are HD types 25 - 38 (see below), and there are also numerous inserted "EB 00" into the code which I guess would slow things down (but I'm no expert). So possibly compensation for the higher clock speed, like you suggested. I asked the previous owner to tell us more in this thread.

But one VERY interesting thing is at 0xE0000 in the combined binary files.

Original:
78X7462 COPR. IBM 1981, 1986
PARITY CHECK 1
PARITY CHECK 2

My version:
286 MOD IBM Internal Use Only
PARITY CHECK 1
PARITY CHECK 2

These are the HDD types:
Type Tracks Heads Sectors Size (MB)
1 306 4 17 10,2
2 615 4 17 20,4
3 615 6 17 30,6
4 940 8 17 62,4
5 940 6 17 46,8
6 615 4 17 20,4
7 462 8 17 30,7
8 733 5 17 30,4
9 900 15 17 112,1
10 820 3 17 20,4
11 855 5 17 35,5
12 855 7 17 49,7
13 306 8 17 20,3
14 733 7 17 42,6
15 0 0 0 0,0
16 612 4 17 20,3
17 977 5 17 40,5
18 977 7 17 56,8
19 1024 7 17 59,5
20 733 5 17 30,4
21 733 7 17 42,6
22 733 5 17 30,4
23 306 4 17 10,2
24 612 4 17 20,3
25 306 4 17 10,2
26 612 4 17 20,3
27 698 7 17 40,6
28 976 5 17 40,5
29 306 4 17 10,2
30 611 4 17 20,3
31 732 7 17 42,5
32 1023 5 17 42,5
33 1024 8 17 68,0
34 583 7 36 71,7
35 915 7 36 112,6
36 1024 9 17 76,5
37 820 6 17 40,8
38 1024 5 17 42,5
 
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SomeGuy

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I can confirm that one of the additions are HD types 25 - 38 (see below), and there are also numerous inserted "EB 00" into the code which I guess would slow things down (but I'm no expert).
That can also be used as a "no operation". One might replace some existing relative conditional jump with an EB 00 to prevent or force execution of some piece of code.
 

vwestlife

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Two years after the 5162 is pulled from the market, someone at IBM France decides to modify the BIOS in a 5162 that they have.
That sounds to me like a technician with time on his/her hands ?

Maybe IBM had a stockpile of unsold 5162s, so they decided to put them to use within the company in some unconventional purpose, which required modifying the ROM.
 

modem7

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Maybe IBM had a stockpile of unsold 5162s, so they decided to put them to use within the company in some unconventional purpose, which required modifying the ROM.
The stockpile hypothesis sounds good, but maybe with a different slant:

It is 1989, and at IBM offices around the world, staff are expecting an upgrade of their office desktop machines from 5160s to something modern, like the recently released IBM PS/2 70 (i.e. 80386DX-16 based). But then the word comes out. As punishment for poor salesmanship of the 5162 a couple of years back, staff will instead be upgraded to 5162s. And, to reduce the resulting decline of staff morale, management decide to have the 5162s upgraded to 8 MHz operation. :)

Right now, I can hear some ex IBM staffers saying, "OMG. How did he get a copy of that internal staff memo?"
 

vwestlife

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It is likely that the XT-286 was created in the first place to allow government agencies, schools, and large corporations to upgrade to 286 power without needing to rewrite contracts and grants that specified "IBM Personal Computer XT" machines. Thus it was never intended to be a big seller on the consumer market, anyway.
 

SomeGuy

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More speculation, but I can easily imagine these machines deployed in some environment (such as industrial) where there were large long-term support contracts in place and plopping down PS/2s might not have been an option. If they needed to reconfigure the machines in some way the original BIOS didn't quite like, IBM probably could have been arsed to hand out a few patched ROMs.

It would be interesting to get the history of this specific machine. Since this was not an official, mass produced release, it really needs documentation on what was changed and why.
 

mrmanse

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It's serial number is BH550121763. It has two ST-225s, an OAK Technologies OTI-067 VGA card (dual output DSUB9/DSUB15), an IBM AT RAM card with 2048k XMS memory, and when I got it it had a panasonic JA-257A 3.5" 1.44M floppy drive (grey bezel). I'm told that it previously was owned by an IBM employee.
 

Anonymous Coward

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Anyone know when the 5170 stopped shipping in France? I am pretty certain I remember reading that they were selling the AT after it had been discontinued in North America. I seem to recall hearing these machines were equipped with XT-286 motherboards, 1.44mb high density drives, 8-bit VGA cards and PS/2 style grayscale monitors. Is it possible that this ROM originally came from one of these later ATs to upgrade this XT-286?
 

mbbrutman

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According to my sources, IBM did a "fire sale" on the XT-286 in June 1987 to clear out the inventory.

BIOS modifications for older IBM machines were a popular hobby inside of IBM. Usually they were done to add hard disk support, but the original XT-286 BIOS had code to limit the speed to 6Mhz and that was a popular thing to fix.
 

mikey99

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I recall there was a special 'IBM Internal Use Only' 286BIOS (for AT and XT-286) that added support for hard drive types 33-38.
The official BIOS supported types 1-32 only.

This BIOS also removed the speed check...... allowing the system to boot with the faster crystal. And it also turned off the NumLock at
boot time.
 

mrmanse

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Yes, now getting somewhere.

And it also turned off the NumLock at boot time.
I'll have to check if numlock is on or off

This BIOS also removed the speed check
Yes, obvioulsy :) And the person I bought the computer from claimed he has another XT-286 at 9 MHz

added support for hard drive types 33-38. The official BIOS supported types 1-32 only
Well actually, Type 1-24 is stock, 25-38 is added.
 

SomeGuy

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Ok can these ROMs also be used in an IBM AT? Just for the added HD support.
I'd think not. There are a few differences that would probably trip it up.

But it is fairly easy to modify an AT ROM using an Eprom and programmer to add drive types. I'm fairly sure there were even some tools that could assist with that.

Or better yet, with the IBM AT it is possible to plop in ROMs from some AT-286 clones that can add built-in BIOS setups and the ability to specify any arbitrary drive size.
 
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