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Soyo 4SA2 only goes up to 64MB memory (16MB per slot)

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First post, by riplin

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Hi folks,

So I have a Soyo 4SA2 motherboard and the manual states that it has support for up to 255(?) megabytes of memory, however, later on in the manual it only lists memory configurations up to 64MB. Another document describing this board gives a huge list of memory configurations up to 256MB memory total. The retroweb page on this motherboard also lists 256MB as the max memory size.

I went digging around and found a comment on a post about a variant of this board that mentioned that 2 sided SIMM support for this board can be enabled by closing pin 1&2 on unpopulated header JP19, but that had zero effect in my case. I checked using a multi-meter and I have continuity from the chipset to the SIMM socket, so I didn't mess that up I guess:

36QQFdT.jpg

Here's an image of the SIMMs that I'm using:

EXSDCQg.jpg

I tried this both with the stock BIOS and a patched version of the BIOS that fixes the IDE LBA bugs, both with the same result:

lJKbxfC.jpg

If anyone has managed to get more than 64MB to work in this board, please let me know! Do I need different SIMMs? Is it a BIOS issue? Perhaps another undocumented jumper header that needs to be changed? I'm all ears!

Reply 1 of 12, by Horun

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Your SIMMS have a very odd chip arrangement for 64MB SIMMs. Yes you need different SIMMS, Single sided with 9 chips. And curious why you want 256MB on a 486 ?
Most 64MB (4MB and 16MB too) 72 pin are Single sided. Only 8MB and 32MB are double sided. It really has to do with Banks or Ranks. Most double sided are double banked or double ranked.
The Datasheet for SIS 85c496 memory controller says "Supports 256K/512K/1M/2M/4M/8M/16M/32M xN Fast Page Mode and EDO DRAM" it does not say 64M: http://bitsavers.org/components/sis/SiS_85C49 … -497_199507.pdf
So with 4 slots max would be 128MB (4x32MB), if your board had 8 slots then 256Mb. No 64MB support... that is my interpetation...
maybe someone else will see this and give their very knowledgeable perspective...

Last edited by Horun on 2023-05-29, 03:01. Edited 1 time in total.

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 3 of 12, by The Serpent Rider

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I see high-density chips (8 memory chips + parity), so motherboard probably can't see full memory size due to chipset limitation. On practice, SIS chipset can recognise low-density 32Mb modules (16 chips). In both cases it means 2Mb per memory chip.

I must be some kind of standard: the anonymous gangbanger of the 21st century.

Reply 4 of 12, by riplin

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Thanks for the response Horun, I wanted 256MB because I thought the board supported it. 😀 No other reason.

Ok, so given that the board only has 4 slots, that limits me to 128MB. I'm guessing since that jumper thing that I read about and tried didn't have any effect, double sided pretty much isn't going to work? So I have to go find some 32M single sided memory? I found some 8Mx40 ECC SIMMS. All the 8Mx36 SIMMS I found thus far are double sided or the seller is selling different chip configurations (not really a risk I want to take).

Reply 6 of 12, by pshipkov

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Try these:

20230528_212500.jpg
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64Mb 60ns FPM.
Overclock well.
Work fine with the SiS chipset version on the Soyo board.

(both sides look identical)

retro bits and bytes

Reply 11 of 12, by maxtherabbit

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riplin wrote on 2023-05-29, 03:27:

Thanks for the response Horun, I wanted 256MB because I thought the board supported it. 😀 No other reason.

Ok, so given that the board only has 4 slots, that limits me to 128MB. I'm guessing since that jumper thing that I read about and tried didn't have any effect, double sided pretty much isn't going to work? So I have to go find some 32M single sided memory? I found some 8Mx40 ECC SIMMS. All the 8Mx36 SIMMS I found thus far are double sided or the seller is selling different chip configurations (not really a risk I want to take).

no you want 32MB *double sided*

Reply 12 of 12, by pshipkov

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@riplin

Assuming you are talking about that Asus PVI rig:
The two motherboards use the same chipset stepping, so it could be a BIOS issue you are facing.
There are multiple BIOS versions of the Soyo board - it is a mess really.
Not sure which one you are using, but you can use the Asus PVI BIOS as a starting point.

retro bits and bytes

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