Help identifying capacity of cache sram chips...

[keropi]

I have the following cache chips on a 486/100 mobo:

4 x Alliance AS7C512-15PC
and 4 x UM61512-AK-15

the mobo only completes boot when it is jumpered at 512kb cache. Are the above chips giving 512kb? because I get HD read errors when things get heavy... it all began when I wanted to upgrade to 512 from 256kb, and added the alliance chips... removing them does not help now, maybe some have gone bad?

 :-(

[RW222]

Typically on older boards when you upgrade the cache you also need to upgrade the "tag RAM" which is the tag store for what is actually cached.

[Jeff]

I was actively building systems back then and I seem to remember Cache and Tag ram being VERY hard to upgrade successfully.  From what I recall anything added pretty much has to be an exact match to what was shipped with the system board for it to work reliably.

YMMV of course.
Good Luck,
Jeff

[DamageX]

I would run a memory test program to verify the problem. (Or if you can't find a suitable program, a simple test is to PKZIP some files and then unzip them... see if you get a CRC error)

Go into the BIOS settings and try a slower cache timing. I remember coming across chips that didn't live up to their specified timings, but would work at a slower setting. Having two different brands of chips in there could also figure in.

[keropi]

thanks for the help!
this morning with a clear mind, I started playing with the cache-size jumpers... I found an alternate setting that gives 256kb (with the original chips) and I have been testing it for an hour... so far so good, I used a DOS ram-cache test, and now I copy the whole C: to D: (~1.2GB)...

[RW222]

I guess you maybe had it set for 256Kbit chips, (32K each) when you have the 512Kbit chips (64K each). 512vs256 might not have made a whole lot of difference anyway. A lot of 486 boards didn't handle things very well and could only cache 32MB whatever you did to them.

[keropi]

so RW222, you say I actually have 512kb cache?
funny, as I have it at 256 now and is rock steady! might worth a try to config it as 512kb again to test, in the meantime I found the manual, the mobo is a Spacewalker HOT-433 , max L2 cache is 1024kb  :-o

[RW222]

The chips marked 512 are 512 Kilobits, they are 8 bits wide so each chip is only 64 Kilobytes, 4 x 64 Kilobytes is 256 Kilobytes. 8x512 Kilobits would give you 512 Kilobytes.

If you take a good look at the manual, you may see an alternative setting for 512 Kilobytes also. If it supports up to 1024 Kilobytes, then it must also take 1024 Kilobit chips. Therefore there would be two ways of having 256 Kilobytes, with 8 256Kbit chips or 4 512Kbit chips, one setting as you see works, the other doesn't. It may be the same for 512Kbyte, which could be 8x 512Kbit or 4x 1024Kbit, you may have previously had it on the 4x 1024Kbit setting.

Shuttle boards of that time were decent quality I think so maybe it will make use of it if you find the right configuration, but remember what settings are working now, in case it really doesn't like those other chips.

[keropi]

thanks for the clarification RW222!
...I used to know all that stuff, but now they seem forgotten...  :-(
after the crashes I got, I kept only the original 4 chips and the extra one, so now I have 256kb. I am gonna keep it that way, since it works perfect and AFAIR 512kb only gave minimal perfomance increase...
thanks!  :-D