RAM for Indigo IP20 and Indy

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tillin9
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RAM for Indigo IP20 and Indy

Unread postby tillin9 » Sat Mar 08, 2008 11:55 pm

I managed to score a free Indy and a box of old RAM, 30 pin, 72 pin, some laptop RAM and a variety of things I don't even recognize (best guess video RAM, cache RAM, etc. for 486 and Pentium I era gear). Anyway... I know the later generation Indigo and Indy take the same RAM. Ideally 32MB modules so I can max out at 384 and 256 respectively.

As far as I can find, the RAM needs to be 36-bit. Sadly I can't seem to find anything which states this on the stick. What's even more odd is that non-ECC modules should be 32-bit. Everything I have seems to be 2M x 40 or 4M x 40. Is this a 9-bit byte ECC issue,. i.e. 4 x 9 bytes with 4 bits for ECC? Also, any idea as the ns rating needed for these two SGIs? Some sites say 60 or 70ns, is this correct or would 80ns work too?

Yes, I know I could just stick it in and check, but that's a great way to ruin machines. My best friend managed to kill a 486 a long time ago this way, with very similar RAM. Anyway... that's why I'm asking. With a better idea that this is the right type of memory, I can limit the final test to ones I know aren't going to cause issues.

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cybercow
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Re: RAM for Indigo IP20 and Indy

Unread postby cybercow » Sun Mar 09, 2008 10:48 am

well ... maybe the most dumb method would be to simple count the number of chips on the simm`s, then if they are all of the same size, because parity chips are often smaller, or have different code, maybe similar but still different ... when counting the chips on the parity simm you will see that when dividing with 8 you will get "strange" numbers

I take one 32M parity stick i have has 2 x 8 chips fitted verticaly and 2 x 4 chips fitted horizontaly
so it have 8 x 2M chips on both sides = 16M x 2 = 32Mb the other chips are for parity ...

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tillin9
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Re: RAM for Indigo IP20 and Indy

Unread postby tillin9 » Sun Mar 09, 2008 2:48 pm

Counting chips doesn't work. The working Kingston RAM in my Indigo and Indy have either 18 or 24 chips. The IBM SIMMs I think might work are all 20 chip. If the 18 chip is non ECC and the 24-chip is buffered ECC, I'm good. However, again I'd like some more confirmation on the specs. of these two machines just to be safe.

kramlq
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Re: RAM for Indigo IP20 and Indy

Unread postby kramlq » Sun Mar 09, 2008 3:56 pm

tillin9 wrote:I managed to score a free Indy and a box of old RAM, 30 pin, 72 pin, some laptop RAM and a variety of things I don't even recognize (best guess video RAM, cache RAM, etc. for 486 and Pentium I era gear). Anyway... I know the later generation Indigo and Indy take the same RAM. Ideally 32MB modules so I can max out at 384 and 256 respectively.

As far as I can find, the RAM needs to be 36-bit. Sadly I can't seem to find anything which states this on the stick. What's even more odd is that non-ECC modules should be 32-bit. Everything I have seems to be 2M x 40 or 4M x 40. Is this a 9-bit byte ECC issue,. i.e. 4 x 9 bytes with 4 bits for ECC? Also, any idea as the ns rating needed for these two SGIs? Some sites say 60 or 70ns, is this correct or would 80ns work too?

I figured the best place for a definitive answer would be the Indy specs, which were released by SGI (check the Linux-Mips site). Here is what it says about memory on pg 16:
The Fast Forward machines will use standard 36 bit wide simms so that the
system will be as open as possible and to reduce cost. There are six
different simms that will be supported: 256Kx36, 512Kx36, 1Mx36, 2Mx36,
4Mx36, and 8Mx36. These need to be 80 ns DRAMS, although the MC chip is
flexible enough to handle different speed parts (see section on Memory
System Controller). All of the simms in a system will need to be the same
speed however.

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tillin9
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Re: RAM for Indigo IP20 and Indy

Unread postby tillin9 » Sun Mar 09, 2008 5:07 pm

Thanks. With that I eliminated all the 40-bit modules and a couple freaky ones. I tested the remainder and they all worked. Sadly, none are 32MB. I have about 18 4MB modules and 10 8MB modules.

SAQ
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Re: RAM for Indigo IP20 and Indy

Unread postby SAQ » Sun Mar 09, 2008 5:28 pm

IBM 40-bit SIMMS. RS/6000, perhaps?

No, those won't work. Like HP, IBM took a standard form factor and proprietarized it. The only thing they'll work in is a RS/6000.
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