Pismo 900Mhz G3 upgrade - so it DID work!

[Byrd]

A good few years back, I bought a Powerlogix Pismo 900Mhz G3 upgrade CPU daughtercard. The seller was parting out a dead Pismo and offered DOA warranty if the parts received didn't work, as he wasn't sure what was dysfunctional. The upgrade card I received didn't show any life, I'd read about them overheating, and he gave me a refund and said to chuck the dead part.

It was put in a drawer and forgotten about. I came across it today, looked it over and noticed some parts of the board were covered in heatsink paste, which I removed. Threw it in my Pismo as a laugh, with a heatsink on top, it booted up without issue! I'll try to rebuild the Pismo now.

The cooling for this upgrade is complete rubbish - it comes with a thin piece of copper that you seemingly put in place of the small L-shaped heatsink, and is simply not enough. It is a 1000Mhz CPU, downclocked to 900Mhz - due to overheating concerns. I'm hoping that if this CPU continues to work, I'll rig up a small fan and custom heatsink inside the Pismo. Interestingly, I just read that you can downclock the CPU using Powerlogix's CPU Director utility for OS 9 and X.

Link demonstrating crappy heatsink

http://www.sterpin.net/uk/pismologixuk.htm

Just goes to show you should always give things a "rest" and try them again (years) later!

JB

 

[Bunsen]

Indeed, crappy heatsink is crappy. Congratulations on getting it going again!

 

[Trash80toHP_Mini]

Just goes to show you should always give things a "rest" and try them again (years) later!
JB

That's some of the wisest advice I've read here at the barracks . . . :approve:

I especially liked the comment about "hot is too hot" }

 

[J English Smith]

Yeah, interesting. If this bumped the Pis up to a G4 it'd be very neat, but the heat trade off here relative to speed seems like a mixed proposition at best...

 

[Byrd]

Sadly, it's doing the weird stuff again. Random booting from cold/mostly black screen/dead/etc. No amount of pressure on the cache/CPU will elicit a response. Cleaned it properly using solvent cleaner. After all the "healing" it did over the past five years, perhaps this is the most I'll ever get out of it!

Interestingly, it uses 512K L2 cache on the die of the CPU, so I could rule out the existing backside cache by disabling it/lifting a pin or two perhaps. Or, I could consider downlocking the CPU to say 700 - 800Mhz, as it behaves like an overclocked Pismo CPU (which I've had experience with - tried doing this to a few 400/500Mhz modules, and this is what they do when you go too high).

Still, a nice project. Or perhaps it should go back in the drawer for a few more years. Still, the first time I plugged it in yesterday, it worked fine until shutdown (but with me pressing a large copper heatsink on the CPU).

JB

 

[Temetka]

If it were me I would run it at 700MHz and move on with my life. Hope it works out for you.