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IBM Personal Computer 100 Type 6260 problems - please advise

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First post, by Socket3

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Hi. I got my hands on an IBM PC100 Type 6260 (dumpster find) and I'm trying to get it up and running, and upgrade it a bit to fit my needs. I have a bit of a soft spot for these old IBM machines, so although I have other (working) socket 7 hardware, I'd love to get this one up and running.

The PC is a budget model, sporting a pentium 75, 8mb of ram (witch at one point was upgraded to 16mb), no L2 cache whatsoever, a CD-ROM and a 800mb disk drive. My plan for it was to have it play late dos games and windows 95/98 games. As such, I upgraded the PC to a 133MHz pentium, 32mb of ram, and tried to add L2 cahce (256kb) and a larger 8gb disk drive. Here I encountered 2 problems:

Problem 1 - the PC is unstable with L2 cache installed. It is configured correctly, and the cache SRAM was taken off a working motherboard. It refuses to enter win95 with cache installed, and sometimes it will hang during boot. I took the sram chips off the IBM and tested them (again) in the motherboard they came with, and they work perfectly. They are 15ns winbond 8kb cache chips. I also tried some 8kb 15ns Elantron? chips - same issue.

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Problem 2 - I can't get any drive larger then 1.6gb to run in it. I tried a 8gb drive and a 4gb drive, both seagate. Both are detected in bios correctly, buy the PC will hang during boot. I even tried setting them as Slave drives alongside the 800mb drive the PC100 came with - it still hang during boot. I could only get it to boot with a 1.6gb drive and it's original 800mb western digital.

Regarding problem 2, I'm thinking maybe a BIOS update might resolve it - unfortunately I have no idea where I can find an updated bios for it. Does anyone know if the old IBM site was archived somewhere? As for problem 1, I noticed the manual states the computer needs one 8kb 3.3v SRAM chip as TAG, and 8x8kb 5v chips... I have no idea what voltage my chips require. The Winbond chips are off a socket 5 motherboard - a Pine Tech PT730

Reply 1 of 9, by Horun

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Odd about the cache chips not running same voltage. Maybe the tag you have is 5v, not 3.3v so it acts up if supplied at 3.3v. Also possible you have all 3.3v non-5v tolerant chips and they do not like 5v supplied to them, Do the main cache chips get warm ? What are the cache model numbers you have ?

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 2 of 9, by Socket3

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Horun wrote on 2020-07-11, 17:46:

Odd about the cache chips not running same voltage. Maybe the tag you have is 5v, not 3.3v so it acts up if supplied at 3.3v. Also possible you have all 3.3v non-5v tolerant chips and they do not like 5v supplied to them, Do the main cache chips get warm ? What are the cache model numbers you have ?

They don't get hot... they barely get warm. I don't have the machine on hand right now, but like I said, I tried several SRAM chips with the same result... It might be the same type of bull$#|t IBM pulled on their older valuepoint systems - the ones that need IBM SIMMs and an IBM "COAST"-like cache FRU. They probably expect the customer to purchase SRAM chips from them.

Any ideas on where to find a BIOS update for it?

Reply 4 of 9, by Deksor

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I had a IBM like this, I never managed to get cache running ...

As for the HDD, I don't think I tried to use a HDD that big 😒

Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 5 of 9, by chublord

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Socket3 wrote on 2020-07-11, 19:39:

Would it be possible that the PSU could be causing these issues? It's pretty old and beat up...

FWIW, I just had to replace the PSU in my IBM Valuepoint because the voltage was low on the +5 and +12V rails. It was obvious with a basic multimeter (+4.36V on the 5V rail).

Regarding the cache, I'm using standard SRAM chips in my Valuepoint and it works. The cache is slow (low bandwidth per Speedsys) but I imagine that's a problem with the chipset and not the cache itself.

IBM Valuepoint 486 DX4-100, Opti 802G, 50 MHz FSB, Voodoo1+S3 864, Quantum Fireball EX 4.0 GB, Seagate Medalist 1.6 GB, 128 MB FPM, 256k L2

Reply 6 of 9, by Horun

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I found a picture of one SC58P VIO sold on Fleabay listed in late 2019 claiming it worked 100% and it has all same chips for Tag and cache: UMC UM61L256k-15
like in this picture

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Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 7 of 9, by Socket3

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That actually helps a lot. Unfortunately none of my boards have this brand of SRAM. Then again, I'm not convinced it matters that much, although I might be wrong. I'm going to test the PC with another power supply - one that I know is good and see what happens.

Reply 8 of 9, by Socket3

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Socket3 wrote on 2020-07-11, 21:28:

That actually helps a lot. Unfortunately none of my boards have this brand of SRAM. Then again, I'm not convinced SRAM manufacturer matters that much, although I might be wrong. I'm going to test the PC with another power supply - one that I know is good and see what happens.

Reply 9 of 9, by Socket3

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Quick update - I resolved the L2 cache issue thanks to @Horun - I used the exact model of SRAMS in the manual and L2 cache works fine now. Apparently there's nothing wrong with the PSU either.

My only current issue - and it's a big one - is that the PC will not detect any drive larger then 1.6GB.... does anyone have a link to a BIOS update for this machine? An IBM driver/software FTP site or archive? Anything?

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