🚀 go-pugleaf

In article <Pine.GSO.3.96.980530071603.697A-100000@lios.apana.org.au>, Craig Dewick wrote:
>
>I've received a batch of 3-chip 30-pin parity SIMM's which I'm going to use
>to build up a couple of sun-4c machines to 64 meg of RAM (they currently
>have no RAM fitted). The SIMM's were sold to me as suitable for sun-4c
>machines by a regular advertiser in the newsgroups.
>
>I've noticed problems with these SIMM's. They pass the POST RAM test fine
>(usually), but when starting the kernel it fails with a watchdog reset.
>I've tried swapping banks around, swapping entire banks out of the
>machine, etc. all with mostly the same result. 
>
>Sometimes the machines will boot, but fail soon after. 

Sounds like it could be a refresh problem.  The x4 devices probably
have different refresh requirements.

>I've noticed that the RAM chips (marked as made by Mitsubishi) are not the
>same speeds, which seems odd. The two 4-bit devices are 70 ns, while the
>single-bit device is 60 ns. I don't see this as being a problem in itself,
>since I'm suspecting the capacitive loading resulting from the SIMM's being
>3-chip instead of 9-chip is what's upsetting the DRAM controllers.
>
>3-chip SIMM's have traditionally been seen, afiak, as a bad idea for early
>Sparcstations. 

A "your milage may vary" issue...

>I did try swapping out all the 3-chip SIMM's for some 9-chip ones I have
>spare from another system, and they worked without a hitch, so perhaps the
>old adage has come out of hiding to show it's still applicable?
>
>What are your opinions about this? I don't think the supplier of the SIMM's
>will object to them being returned if there is a genuine problem since I'm a
>regular customer. 8-)

Usually it's adequte to say that they didn't work in your application
and trade for 9-chip ones.  It can be more of a battle if your supplier
had to special order or doesn't have 9-chip versions to exchange.

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