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Upgrading embedded S3 Trio 64 to 2MB in IBM PC 350

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First post, by wbahnassi

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Hi. On an IBM PC 350 Pentium 75Mhz machine, is an embedded S3 Trio 64 chipset with 1MB video memory. It also has 2 sockets for upgrading video memory to 2MB. So I took 2 memory chipsets from a working 2MB stand-alone S3 Tri 64 PCI VGA card, and shoved the suckers into their slots on the IBM mobo.. but nothing happened.
BIOS still says I have 1MB video memory, and trying to use higher resolutions in Windows 3.11 fails with out-of-video-memory error.
I looked around for any jumpers that would tell the system about the additional 1MB video memory, but couldn't find any.

Wondering if I missed anything or if anyone did this upgrade before.

Here they are in their new slots:
20211020-145442.jpg

Also wanted to mention the standalone card was successfully using all its 2MBs without issues or corruptions, so the chips extracted from it should be working.

Reply 1 of 5, by Warlord

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It's upgradible. Only thing I can think is those are not compatible or theres a jumper thats not documented somwhere I could find.

The documents say
The video memory modules used are 256 KB x 16 (512 KB total) 60 nanosecond (ns) EDO DRAMs.
The system is shipped standard with two modules that total 1 MB and create a 32-bit data path to video
memory. An upgrade is available that increases the total video memory to four modules or 2 MB and
creates a 64-bit data path to video memory. The maximum amount of video memory that can be used
with the video subsystem is 2 MB.

What I would do is pull up the data sheet for the integreated ram, then search for some SOJs that match the spec. Since I looked at the datasheet for the SOJs you added and while I think they could maybe work they obviously don't and that could be becasue the specs are a bit differnt.

Reply 2 of 5, by Datadrainer

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It is common for Trio64 BIOS to autodetect the memory. All the modules are EDO DRAM with FPM of 256Kb x 16 banks (2 x 512KB) and the added ones are 45 ns against 60 ns for the ones on the motherboard. All the modules are placed correctly and should then work at 60 ns without problem.
And we can see here that there is no jumper settings [http://ps-2.kev009.com/pcpartnerinfo/ctstips/93e2.htm]. So it should work.
Maybe there is something to change in the BIOS configuration menu to enable the new MB.
Or maybe you damaged one or both chip with an electrostatic choc during removal or manipulation.

Edit: But as faster modules should work at slower speed, it is not always the case, and the general rule is to always use modules with the same specifications.

Knowing things is great. Understanding things is better. Creating things is even better.

Reply 3 of 5, by wbahnassi

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Datadrainer wrote on 2021-10-21, 20:05:

Or maybe you damaged one or both chip with an electrostatic choc during removal or manipulation.

Probably that's what happened. Because I put them back in the card and now it no longer recognizes 2MB, but only 1MB 😑

Or maybe I'm not putting them correctly in their sockets despite me pushing them in quite well.

Reply 4 of 5, by BitWrangler

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They do look like they're sitting a little high, those kind you really have to mash in, often with a disconcerting **SCRAUNCH** noise until they bottom out.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

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