re:cache
In message "cache", wojtek@dracula.gda.osk.pl writes:
> I've just repaired my mainboard. Everything is working (all soft), but
> my cache is not detected.
>
> In instruction (AXPpci33 OEM Design Guide,PS format), they show's how to
> install
> cache:
>
> SSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
> CCCCCCCCCCCCCCCCCCCCCCCCCCCCCC (1) C-contacts, S-socket
> SSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
> CCCCCCCCCCCCCCCCCCCCCCCCCCCCCC (2)
> SSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
> SSSSSSSSSSSSSSSSSSSSSSSSSS
> SSSSSSSSSSSSSSSSSSSSSSSSSS
> SSSSSSSSSSSSSSSSSSSSSSSSSS
> SSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
> CCCCCCCCCCCCCCCCCCCCCCCCCCCCCC (3)
> SSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
>
> It's written, that 32kx8 chips (256KB cache) should be installed
> in contacts 2+3,and 128kx8 chips (1MB cache) in contacts 1+3,
> and it's shown that they are longer and wider than 256KB chips.
>
> Mine is only longer, but not wider, so i cannot put it in 1+3 contacts
> without pin deformations.
>
> Should i do it, or it is not the reason why my cache doesn't work
My apologies for not responding to this sooner.
It is the reason your cache doesn't work. I had exactly the same
problem. The situation seems to be as follows.
The AXPpci33 was apparently designed with the assumption that 128Kx8
cache chips would always be 400mil wide. It seems that these are now
being phased out in favour of the 300mil package. Pins 31 and 32 of the
300mil socket on the AXPpci33 are not connected to anything, and pin 30
has a different function on the 32-pin 128Kx8 chip than the
corresponding pin 28 on the 28-pin 32Kx8 chip. All the other common pins
have the same function on both parts, and the 300mil and 400mil socket
holes are connected together (I verified this with an ohmmeter).
Therefore, what you need to do is bend pins 30, 31, and 32 on the 300mil
chip so that they go in the 400mil socket. If you bend them at the right
angle, they should still be long enough to make good electrical contact.
I was able to get a good fit mechanically; I haven't yet powered up the
board to see if it works. I can't see any reason why it wouldn't. If you
want to verify my analysis, you can get PDF spec sheets (with pinouts)
for the 32Kx8 and 128Kx8 SRAMS here:
http://www.alsc.com/product/prod-index.html
See the AS7C256 and AS7C1024 parts. By the way, if anybody needs more
cache chips, these ones are really cheap, and the spec sheets include a
list of distributors.
I hope this helps.
Ian Willmott
Northern Telecom
Ottawa Ontario Canada
willmott@nortel.ca.nospam.org (remove everything after 'ca' to reply)
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