🚀 go-pugleaf

Hi folks,

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.

However, I'm having troubles...

The modules's are QSIMM QS944x4LP's, and are dated as being made on the 11th
week of this year (1998), The RAM chips are surface mount, resulting in
modules that are extremely thin (about 3.5mm from the back of the PCB to the
top of the device encapsulation).

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. 

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. 

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-)

Regards,

Craig.

--
            Craig Dewick. Send email to 'cdewick@lios.apana.org.au'
  Point a web browser at 'http://lios.apana.org.au/~cdewick/sun_shack.html' to
    access my archive of Sun information and links to other places. For info 
      about Sun Ripened Kernels, go to 'http://www.zeta.org.au/~craig/srk'