VOGONS


First post, by RobDos

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I purchased 1x UM61512AK-15 64x8 and 8x IS61C1024-15N 128x8 DIP-32 SRAM modules for my PC chips M915I board, after installing the system will start to post but hangs when it switches over after detecting the hard drive, disabling cache in the BIOS will let me boot the OS.

According to the manual I can use 8x 128Kx8 and a 64K x8 to get 1MB of total cache. I did try pulling 4 of the chips, and evening changing the 64K chip for a 128 but always the same (on occasion I did get funky characters). Each time configuring per the the jumpers.

So, a few questions

1. If I use a larger capacity chip in the slot and configure for a lower capacity, should it work? IE: only use 64K of the possible 1024K.
2. Likely the above one answers this, but if I use a TAG ram that exceeds the capacity f the manual would it work? IE use a 64K tag ram when the configuration calls for 32K
3. Is there anything I can do to check to see if they are fake chips
4. What speed of SRAM should I use, I've seen 10-15-20 and even 8, it's a 486DX2 intel.

ISSI
IS61C1024-15N
The second number varies on the chips i received, JV530151L 0108

P3 Slot 1 - 512MB PC100 - 128GB SSD - RADEON 9200 SE , SB Awe64 ISA - GOTEK MOD

Reply 1 of 4, by Deksor

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For a dx2, even 20ns should work. Can you post a picture of your mod ?
Make sure that the chips are properly inserted in the sockets and you didn't bend any pins.

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

Reply 2 of 4, by mkarcher

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RobDos wrote on 2021-12-22, 01:32:

I purchased 1x UM61512AK-15 64x8 and 8x IS61C1024-15N 128x8 DIP-32 SRAM modules for my PC chips M915I board, after installing the system will start to post but hangs when it switches over after detecting the hard drive, disabling cache in the BIOS will let me boot the OS.

This is the typical symptom of cache memory being bad, but not bad enough to be detected as "not present" by the POST. The cause could be the memory chips, or the board itself, like a broken address trace to the cache chips.

RobDos wrote on 2021-12-22, 01:32:

1. If I use a larger capacity chip in the slot and configure for a lower capacity, should it work? IE: only use 64K of the possible 1024K.

That depends on your board. If you configure for 64K cache, some address inputs of the cache SRAM chips are not used anymore. It will work if they are tied to a fixed level. It will fail if they are floating or still connected to host address lines. Don't count on larger chips working fine unless you reverse engineered how the cache size jumpers work.

RobDos wrote on 2021-12-22, 01:32:

2. Likely the above one answers this, but if I use a TAG ram that exceeds the capacity f the manual would it work? IE use a 64K tag ram when the configuration calls for 32K

Again, this depends on your board. Generally, if the chip is larger than the largest chip supported by your board, you don't have to be afraid of excess address bits being tied to actual address lines, but you might need to add a pull-up on the extra adress lines. Usually, using 1024 KBit chips for the tag RAM in boards that support 1M cache is no problem.

RobDos wrote on 2021-12-22, 01:32:

3. Is there anything I can do to check to see if they are fake chips

There appear to be lots of untested SRAM chips with fake ISSI labels (especially the 10ns variant that never existed in DIP package) on them. You might have gotten a batch of them. The rule of thumb is to expect a dead-on-arrival rate of 10%, so you shouldn't have more than two bad ISSI chips. Jumper your board for 512K cache (single bank), and try different sets of your 8 ISSI chips.

RobDos wrote on 2021-12-22, 01:32:

4. What speed of SRAM should I use, I've seen 10-15-20 and even 8, it's a 486DX2 intel.

Chose the slowest cache settings ("3-2-2-2") for start. That should probably even run with 25ns RAM at 33MHz FSB. If the board fails at that cache settings, something is severely broken (either the board or the chips.

Reply 3 of 4, by RobDos

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Thanks for the tips, I did try swapping around chips last night dropping it to 512K and was able to get different failures (blinking colors, goes to the next screen and stays blank or just reboots after the hdd detection) but never a full post. I suspect I've been dupped, filed a claim with ebay and ordered some UMC chips, 64k and 32K. So one way or another if it's not the board I ought to get some cache in there! 🤣

Someone suggested the board depending on the revision of the chipset also may have issues with 1MB Cache but I have no way of testing.

Tried reaching out locally to a Ottawa (region I'm in) group but no luck.

I appreciate the feed back and help!

P3 Slot 1 - 512MB PC100 - 128GB SSD - RADEON 9200 SE , SB Awe64 ISA - GOTEK MOD

Reply 4 of 4, by Deksor

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Can you take a picture of your chips ? They might indeed be faked.

Try to scrub them with alcohol and a Q-tip. If there's paint that comes off of it, it's definitely faked. However even if it doesn't go away it can still be faked. There are other signs of faking that can be seen

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