Help getting 486slc2 upgrade working reliably with my PS/1 system \ VOGONS

Help getting 486slc2 upgrade working reliably with my PS/1 system

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First post, by keropi

Posted on 2018-10-16, 10:30

keropi Offline

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Hiya!

I recently acquired a brand new Make-It 486 upgrade for 386sx processors. I opened it, installed it in my PS/1pro system and booted - I was not expecting any troubles since in the past I had a cyrix 486slc2/50mhz upgrade on this system and it just worked. But the old upgrade only had 1kb of L1 cache (and speed difference was nothing special for me so I just sold it again) - the new one has a TI cpu with 8kb of L1 cache and the speed boost is very noticeable (wolf3d went from 11.7fps to 29fps!) .

Long story short the upgrade is not working reliably, most of the time the system boots with an error code 102 meaning "system board error" according to the manual.

What I have tried is this:

- 386sx and upgrade pins cleaned
- tried on a 2nd spare motherboard I have, both have 1992 BIOS but one is labeled 08/04/1992 the other 26/06/1992 both behave the same with the upgrade
- tried swapping BIOS chips between mobos just in case
- tried only with the onboard 2mb ram, with a new CMOS battery after clearing and re-doing the BIOS settings
- tried with onboard or ISA vga

Nothing made any difference. The motherboard(s) in question is an IBM 87F4769 one:

Any ideas what to try next? Do I need a BIOS update for the TI486slc2 cpu? (the only bios source I know is on the IBM PS/1 Resource Page and I was the one that submitted the image 🤣 )

Open to all suggestions as I would really like to use that upgrade on this system. Thanks! 😊

🎵 🎧 ⏳ ⚡ PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website

Reply 1 of 5, by stamasd

Posted on 2018-10-16, 11:47

stamasd Offline

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Is it one of those upgrades that clips on top of the 386sx? I've never had a make-it 486 so I have to ask.
Do you have another 386sx motherboard apart from the other one you tested to try the upgrade in? Essentially, can you make the upgrade work reliably in any motherboard? Goes to troubleshooting if it's a problem with the upgrade module, or the combination upgrade+motherboard. It's not unheard of to have faulty chips even new out of the box.
Is the extra cache disabled or enabled when you boot?

I/O, I/O,
It's off to disk I go,
With a bit and a byte
And a read and a write,
I/O, I/O

Reply 2 of 5, by keropi

Posted on 2018-10-16, 13:13

keropi Offline

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Location: Greece

Yes the upgrade clips on top of the 386sx cpu just like the previous one.
ATM I don't have any other "normal" 386SX mobos to test it except a 386sx33 SBC that I must invest a couple of hrs to test... I don't think the upgrade is damaged, a dead cpu would just result in a blank screen not error codes being displayed IMHO. The L1 cache is disabled on boot-time, there is a utility that runs from autoexec.bat that enables it.

I thought about replacing the caps on the upgrade just in case they affect stability but these are ceramic and tantalums so I don't think I need to, right?

🎵 🎧 ⏳ ⚡ PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website