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IBM 5322 - System/23 - help needed - ROM image

A

alexfloca

Experienced Member
Joined
Jan 27, 2012
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Transilvania, Romania
Hi guys,

I am now the proud owner of an IBM System/23. Unfortunally it seems one of the ROM's ("ROS" as it is called in the technical manual) is broken. Could anyone help me with the ROM image for me to burn a replacement eprom ?
The power up diagnostics points to the "0B" circuit on the motherboard, i could identify this with the help of this document -> https://gitlab.com/NF6X_Retrocomputing/system23/blob/master/docs/IBM System 23 Model 5324 MAP.pdf (found on page MAP 1200-5)

I would love to get this system up and running..

have a nice Sunday!
Alex
 
NeXT said:
how is it broken? Bit rot? broken pin? corrosion?
Click to expand...


no physical damage can be seen. the power on test fails with "0B" blinking in reverse video pointing out the CRC of this ROM chip is bad... could one bypass this error and let the system run with the bad/incomplete rom basic?
 
alexfloca said:
no physical damage can be seen. the power on test fails with "0B" blinking in reverse video pointing out the CRC of this ROM chip is bad... could one bypass this error and let the system run with the bad/incomplete rom basic?
Click to expand...

how far in is this check? has it checked any other ROM chips? ROM chips are usually pretty solid, its PROMs that go bad. If there is TTL anywhere then that could have failed. I guess it must have some good ROM if it can run the ROM checksum code?
 
The System/23 started and did the power on checks, only the ROM "0B" failed, today i leaved like this for 10 minutes and it died completely, no video. i suspect also there could be one of the logic chips bad in addressing the eproms but unfortunately all chips are marked with ibm codes no 74xxx or 54xxx or similar and with no schematics it will be a hard project, it could also happen that a second eprom is bad now or the ram board or anything else... will not give it up yet, i hope there is someone out there with a circuit diagram for this....
 
ok, monitor gone bad, fixed the monitor... stuck with the ROM/EPROM "0B", can anyone identify the type of ROM / EPROM in the system 23? everything is marked by ibm with custom circuit numbers, eproms, ttl's, processor, everything is custom marked
 
That's pretty easy.

My initial guess is that it used the same ROM that the 5150 used. Looking at the service manual, page 2-52, confirms this. The ICs are 24 pin and are identified as having 8KB each for a grand total of 128KB (16 chips).

The only EPROMs that I'm aware of that will work are the Motorola MC68765 and 68766. There's one other manufacturer that made these 64 Kib 24-pin EPROMs, but it slips my sieve of a mind at the moment. You can get adapters to adapt 28 pin EPROMs/EEPROMs, which are far more common.

Ah, found it--the WS57C49C is also a match. There may also be a few bipolar PROMs that would work.
 
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alexfloca said:
ok, monitor gone bad, fixed the monitor... stuck with the ROM/EPROM "0B", can anyone identify the type of ROM / EPROM in the system 23? everything is marked by ibm with custom circuit numbers, eproms, ttl's, processor, everything is custom marked
Click to expand...

If you look on the Imagewriter section of bitsavers, some of the Intel part numbers have been decyphered.
The 24 pin 8K ROMs there were readable as the Moto types that Chuck mentioned in the Imagewriter.
 
Well, I checked mine and sadly, it dies on the power on diagnostics with an error "13" (I am assuming the highlight is an error) :( The error looks like this:

IBM 5322 error 13.jpg


I pulled out the motherboard and cleaned off the dust but still got the same error. Here is a pic of the motherboard and the ROSes on it. Both "13" and "0B" are soldered on. Refer to PDF page 13 of this document for locations: http://bitsavers.org/pdf/ibm/system23/fe/IBM_System_23_Model_5324_MAP.pdf

Here is a high-rez pic of the motherboard: http://vintagecomputer.ca/wp-content/uploads/2018/06/IBM-5322-planar.jpg

Will have to look a little further into this tomorrow or the weekend.
 
Ok. Looking over this page for the 5150 ROMs http://www.minuszerodegrees.net/5150/motherboard/5150_u33.htm I am guessing the EPROMs can be Motorola MCM68766's? I'd love if someone could confirm. I have MCM68766Cs and a programmer that will do them. I can desolder the "0B" ROM and read it and send the ROM image or I can create you an "0B" copy. If you could do do the same for "13", that would be awesome.
 
Al Kossow said:
I've checked with a couple of people who have them, and they are VERY reluctant to unsolder them to read.
Click to expand...

I passed my System/23 on to another collector (who was involved in its development!) a couple years or so ago. If I still had it, I wouldn't be reluctant to unsolder ROMs and dump them. I'm not saying I'd ever actually get around to doing it, but that would be a matter of procrastination, not reluctance.
 
My TopMax programmer is able to program MOTOROLA MCM68766 EPROMs but when I attempt to read one of the ROMs, I get an insertion error. I will try to read one and program an MCM68766 (that does not give me an insertion error) and see if it works. Hopefully I don't damage the ROM.
 
NF6X said:
I passed my System/23 on to another collector (who was involved in its development!)
Click to expand...

I asked him, and he doesn't have any way to read them.

It may come down to trying to find someone who canibalized one for the keyboard, or try to find a scrapper that has a loose board.

The other problem may be mixing roms between different firmware revisions. It would be a good idea to write the IBM part numbers down
from the two failing boards to see if they match.

--

I put copies of the planar picture and the rom/eprom data sheets on bitsavers under http://bitsavers.org/pdf/ibm/system23/firmware
 
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For reading, one of those 24-to-28 pin adapters used for the IBM PC and other systems may be a decent bet. You probably still won't be able to program the things, but you'll be able to read them.
 
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