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Intel 430HX and >64M cacheable RAM

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First post, by mpe

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Trying to upgrade my Triton II based motherboard (GA-586HX 1.55) to get cacheable RAM > 64M.

In stock config there is 256kB L2 cache and one 16kx8 SRAM TAG chip onboard + one empty 28pin socket.

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Both of my COAST modules are 256kB and they have their own TAG SRAMs:

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So when I put one of these in the COAST slot, I'll get 512kB L2, however the cacheable range is still only 64M.

There is a BIOS setting that flips between 64M and 512M. However, the board doesn't POST when I set this to 512M no matter if with COAST module or not. I was hoping the chipset would use the extra tag on the COAST to get the extra cacheable range, but it doesn't seem to be the case.

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So I am wondering I need to put something to the free SRAM socket. Unfortunately, I don't have a 16kx8 12ns chip, but I have abunch of 32kx8 15ns which should be compatible AFAIK. However, when I put this one in the board doesn't even start.

Any idea how to get this working? Do I need some sort of special tag chip?

Blog|NexGen 586|S4

Reply 1 of 7, by The Serpent Rider

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According to the manual, you need to install additional SRAM to cache 512Mb. And yeah, 16kx8 chips only (15ns or better).

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

Reply 2 of 7, by mpe

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Thanks. Need to go shopping for that 16kx8 to see if it helps. I wonder why can't they just use the one on the COAST and combine it with the one on board. Looks like they are just using PBSRAMs when a module is inserted.

I'd love to understand better how this works.

Anyone has a copy of Intel document called "Flexible Cache Solution For the 430FX/HX/VX PCIsets" they can share? This is referred in numerous Intel datasheets, but I wasn't able to find it online.

Blog|NexGen 586|S4

Reply 3 of 7, by The Serpent Rider

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I think additional TAG must match size of the one which is soldered on board. 256Kb COAST modules TAG usually won't match.

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

Reply 4 of 7, by auron

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actually, 32kx8 should in fact work. if you google for GA-586HX images, you may see several boards that have such chips plugged into the second tag socket.

now as to why your board doesn't boot with that chip inserted, even with the COAST off, did you make sure your SRAMs are working good? if it's the relabled parts with brown writing and iffy date codes, you may need to test a couple of them until one actually works. regarding the tag on the COAST, i would assume it's just not designed to use that, given that there already is a 16kx8 chip on the board. the ISSI SRAM on your COAST is just 8kx8.

just out of curiosity though, what do you intend to run on a K5 that needs >64 MB RAM? or is it more of a "just because" thing?

Reply 5 of 7, by mpe

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Yes. The 32kx8 chip should be working as it was a pull from one of my 486 boards where it is working fine.

Since there are no jumpers I wonder if the chipset scans the tag bits at reset trying to identify the size and it fails due to using non-matching chips.

Yes. It is "just because" reason. I am working on a project documenting and comparing performance differences between early Pentium chips and chipsets. I would like to better understand implications of non-cached RAM under specific workloads.

Blog|NexGen 586|S4

Reply 6 of 7, by The Serpent Rider

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if you google for GA-586HX images, you may see several boards that have such chips plugged into the second tag socket.

Revision probably matters. Or maybe it's early BIOS version bug.

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

Reply 7 of 7, by RacoonRider

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A long time ago I played around with Asus P55T2P4, a 430HX board. It already had maxed out cache (no COAST slot) and I know for sure that both 16k8 and 32k8 SRAM chips worked. I tried a few 12ns and 15ns chips and they all worked.

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