Small form factor daughtercard CPU heatsink mounting

[jessenator]

Figured I'd start a topic for this separately

So what I've noticed is that the larger, OEM-like CPU daughtercards had quite a large footprint, and would have a proportionally large heatsink; ergo the mounting would be able to span the card.

Upgrades, especially later 1990s and early 2000s had a much smaller PCB footprint and (apparently) had more compact heatsink mounting solutions. Mine was absent on the PowerLogix card in my PowerWave, and want a good solution.

I made progress on my own but paused to ask any willing forum members to photograph what their cards' mounts look like. Here's what I've done so far: measured the PCB, the CPU substrate, got specs and measurements of the gaps and based my drawings off photographs of what I could find.

The original, circular heatsink appeared to be 54mm diameter. I wonder what solution they have, because there's only a 6mm gap between the CPU and the dip switches, the 755 package being 25mm square.

There's only ~1mm clearance between the PCB and the bottom of the CPU

That is a not-quite-engineering-correct representation of a 27.94mm heatsink i found, that actually has a photo reference of a 604 PPC chip in it! Found it on Mouser, I'll post the link later.

I'm working with a friend on the 3d printing and testing material tolerances.

Anyhow, I hope this is roughly on the right track, but would appreciate any additional insight.

 

[jessenator]

Heatsink mentioned above. I find it humorous that many of the Wakefield Vette heatsinks are shown with various PowerPC chips
https://www.mouser.com/ProductDetail/Wakefield-Vette/658-60AB?qs=sGAEpiMZZMttgyDkZ5Wiuita4PD18Ap7Tf5wpPPbMBU%3D

 

[waynestewart]

I have some powerlogix cards so if you want any measurements I can do that.

However if I had to make my own heat sink, I'd go bigger than stock

 

[jessenator]

I have some powerlogix cards so if you want any measurements I can do that.

However if I had to make my own heat sink, I'd go bigger than stock

I'd love some images of how they attach, if that's feasible.

Do the G3s get that hot? Based on nothing, I thought they were a tad more efficient than the 604s, but correct me.

I wonder if anyone carries the short and wide heatsinks like sonnet had on their crescendo line.

If it did go edge to edge, it might be easier to secure around the PCB edge instead of the CPU itself.

My biggest concern is that dipswitch box and clearing it. Although if I somehow found a 25mm tall, and much wider heatsink it looks like it would clear.

 

[waynestewart]

On mine the heat sinks are just glued on.

I won't be home tonight until after 11 but I'll get some pics tonight or tomorrow.

The G3s don't get as hot as the 604 and likely owners now aren't doing heavy computing with those machines like many were back then. Still if I had to add a heat sink I like the idea of extra cooling.

 

[waynestewart]

I pulled out my power logix cards and I misremembered how the heat sink was mounted. There was a plastic clip that hooked onto the processor and the center of the heat sink was threaded and screwed into that clip. Pictures will help

 

[jessenator]

Thank you!

Well that explains the clearance issues with a normal heatsink. But this makes me a bit more confident with the direction I'm going with the mount currently.