[rescue] Sparcstation 20 - Dude, we're getting the band back together!

[Sanford Barton]

Guys, I've been having a blast (sorta), refurbishing an old Sparcstation 20.

So, finally, I can afford to put together that ultimate SS20 that I
lusted after back in 1995!! But I've run into some issues that I'm not
sure if they are normal or if I need to keep digging, so heres the
story:

I built this machine in an Aurora 2 chassis (the one with the better
cooling and full-height cd-rom).  I'm using a later rev motherboard
that has the newer sbus controller.  In the drive bay I have 1x 72gb
seagate cheetah (actually runs cooler than the older, smaller drives
of the era).  I have an 8mb VSIMM for the video and run Xsun in 24bpp,
and 448mb RAM. The PROM is 2.25R.

For processors I have a pair of SM71's and a pair of SM81's at my
disposal.  I also have a pair of ROSS 200Mhz and a pair of 150Mhz, but
I really, REALLY, would rather use the SuperSparcs in this machine
because they wipe the floor with the ROSS in general
desktop/multitasking usage.

I've loaded Solaris 9 and the latest recommended patch bundle as well
as several other patches for gtk apps, etc.

So here's the problem.  With the ROSS processors the above system is
rock solid, everything works as expected.

With either the 2 x SM71s or  2 x SM81s, the system runs fine until I
start the stress it with a few modern apps like Seamonkey,
Thunderbird, Pidgin, etc.  These newer apps put a lot of load on the
CPU's in the form of context switches and cache (which the SuperSparcs
excel at).  But after about 10 minutes of usage like this, the machine
locks up solid and must be power cycled.  An easy way to reproduce
this is to scroll a large webpage up and down continuously for about
20 seconds.  That really spikes the CPU usage and will always leads to
a lockup.  Like I said, with the ROSS processors, I could do that all
day long with no issues.

For testing purposes, the top of the case is removed and  supplemental
cooling on the cpu modules to produce a best-case baseline for heat
management.  I'm very familiar with the heat challenges in the aurora
cases, especially with the faster processors, but I would say as a
general finger test, the SuperSparcs are generally running a tad
cooler then the Hypersparcs, even after I reconditioned the heat sinks
with new thermal compound.  I have also applied new thermal compound
to the memory and subs controller heat sinks.

Things I think I can rule out:

-  Motherboard (tested with spare, no improvement)
-  Power supply (tested with spare,  no improvement)
-  Memory (tested with spares, no improvement)

So where I'm at is basically 4 possibilities:

1.)  I'm taxing the SuperSparcs in such a way with the newer software
that they will never be stable in this system.
2.)  I have a batch of bad processor modules.
3.)  The CG14 bits are being pushed beyond their limits with the
SuperSparcs, especially now that it's not using much acceleration for
2D (speculation).  If so, why not the same behavior with the ROSS
processors?  Perhaps they are not able to feed/stress the
memory/graphics controller they way the SuperSparcs are?
4.)  Not a heat or component stress issue at all, but some sort of
multitasking, OS, or cache/memory controller bug.


Any ideas, experiences, hope, discouragement, anything??

Thanks!