Shine a light from the back to the front.

Those marks look like they don't even have the ground plane attached to them from what I can see in those pics you posted.

An Xray may not reveal what you think. If you check some other vid cards you will see nylon heatsink tabs to attach a heatsink but they are never that close to the chip.
Those 4 points are for SMC alignment and they are probably a bad place to drill.
Sorry but have always had an issue with taking a perfectly working vintage part and overclocking it. Yes have done it myself but have come to realize that ruining a 30 year old part to gain 10 or 20% is just not worth it...
Just my opinion...

Don't. What's wrong with the old school use normal thermal paste, wipe away two corners, two small dabs of superglue on said corners- heatsink on top?

cyclone3d wrote on 2021-08-26, 00:52:

Shine a light from the back to the front.

Those marks look like they don't even have the ground plane attached to them from what I can see in those pics you posted.

Yes, I tried this. There is solder mask on the back that is impermeable by light.

Horun wrote on 2021-08-26, 00:57:

Sorry but have always had an issue with taking a perfectly working vintage part and overclocking it. Yes have done it myself but have come to realize that ruining a 30 year old part to gain 10 or 20% is just not worth it...
Just my opinion...

I happened to come across a box of these accelerators so I am in a very unique situation where experimentation is now necessary to satisfy my curiosity.

Byrd wrote on 2021-08-26, 01:45:

Don't. What's wrong with the old school use normal thermal paste, wipe away two corners, two small dabs of superglue on said corners- heatsink on top?

That sounds permanent. Why glue when you can drill?

If you do decide to drill, you better make sure you have a precision drill press and a way to hold the card in place really well. One slip and the card is dead.

You will also have to be 100% sure that you get any of the dust and bits of stuff from drilling off the card or else you have a good chance of shorting stuff out.

Another option is to use fishing line and springs to secure the heatsink. The springs of course will be on top of the heatsink or in channels in the heatsink. You would have the fishing line going around the card top to bottom. I've done this before and it works well.

I've also use the thermal paste with dabs of superglue on the corners and that works ok but I always had the heatsink come loose after a while. Probably due to the thermal cycles eventually weakening the super glue to cooler and chip connections too much.

cyclone3d wrote on 2021-08-26, 02:16:

If you do decide to drill, you better make sure you have a precision drill press and a way to hold the card in place really well. One slip and the card is dead.

I would not attempt this without a drill press. I'm not THAT crazy.

cyclone3d wrote on 2021-08-26, 02:16:

You will also have to be 100% sure that you get any of the dust and bits of stuff from drilling off the card or else you have a good chance of shorting stuff out.

A little bit of Silly Putty or adhesive tack would prevent bits from getting stuck underneath the QFP. The rest of the board can be washed in the sink afterwards to be safe.

a drilled hole is also permanent :p

just clamp it on or use higher quality sticky thermal pads with a decent thermal conductivity, this tape is probably bottom of the barrel and meant for just really basic low power electronics... and make sure to use a pad as thin as possible, thick pads are merely meant for bridging gaps

Thermal paste would also be better than thermal epoxy. I haven't seen any that I would actually want to use if I had a choice.

Linus did a great video on a thermal epoxy:

https://www.youtube.com/watch?v=WJnrMNCahxc

Drilling holes in a PCB is a terrible idea.

Get a PCI fan bracket from Amazon, install two Noctua 12cm fans on it and place it directly below the PowerVR card. That should be enough for all your cooling needs.

imi wrote on 2021-08-26, 02:24:

a drilled hole is also permanent :p

just clamp it on or use higher quality sticky thermal pads with a decent thermal conductivity, this tape is probably bottom of the barrel and meant for just really basic low power electronics... and make sure to use a pad as thin as possible, thick pads are merely meant for bridging gaps

Probably much easier to use a small c-clamp over the card with a thin insulating pad on the back of the card for one side of the clamp while using the other side pressing down on a generic heatsink, probably way less chance of hurting the card than drilling.

If it was my card I would make a delrin frame that hooks over the top edge and fasten through the 3 existing holes on the card with clearance for the components on the card and a opening for a custom machined heatsink and mounting/tensioning mechanism built into the frame but probably not as that would be alot of work.

Grem Five wrote on 2021-08-26, 02:40:

If it was my card I would make a delrin frame that hooks over the top edge and fasten through the 3 existing holes on the card...

The problem that I'm trying to solve is that the PCX2 does not have any existing holes anywhere on the card. 😀

Kahenraz wrote on 2021-08-26, 03:03:

Grem Five wrote on 2021-08-26, 02:40:

If it was my card I would make a delrin frame that hooks over the top edge and fasten through the 3 existing holes on the card...

The problem that I'm trying to solve is that the PCX2 does not have any existing holes anywhere on the card. 😀

It has the 2 holes that the pci cover mounts to and the 3rd hole on the lower end of the card opposite side of the cover, hence I said a frame akin to a backplate on a modern gpu but on the other side of the card. Being a machinist I tend to over think things and come up with complex solutions when there are simpler and more practical solutions like a clamp. https://youtu.be/tExiEsBy4Bo?t=576

Ingeniously used cable ties can practically be made to do miracles and their use is eminently reversible and non destructive .

EDIT : thread subject made me think of this : https://youtu.be/1i3gp_aN1cs?t=129 😉

Grem Five wrote on 2021-08-26, 03:20:

I tend to over think things and come up with complex solutions when there are simpler and more practical solutions like a clamp. https://youtu.be/tExiEsBy4Bo?t=576

This is especially relevant to VOGONS as there is a photo of exactly this by a 3dfx engineer testing the unreleased Rampage.

Grem Five wrote on 2021-08-26, 03:20:

It has the 2 holes that the pci cover mounts to and the 3rd hole on the lower end of the card opposite side of the cover

In that case I count four holes! There is one cleverly hidden above the voltage regulator if your card happened to make it safely through the wave solder bath without getting plugged up. It will also depend on how large of a regulator was used on your particular card.

The Matrox M3D also has your "third" hole elsewhere on the board and no secret hole by the voltage regulator.

Whatever is made to cool this chip, it will have to be either custom or semi-custom and probably won't be able to fit everyone's card.

heres a crazy thought. Since the cards were designed to be able to run without a heat sink, why then would just normal adhesive thermal tape to hold a small heat sink on not me way more than adequate. even the cheapest 3w tape would be more than enough. There is 12w tape which would be overkill.

Kahenraz wrote on 2021-08-25, 23:55:

I would like to experiment with overclocking the PowerVR PCX2 by replacing the onboard quartz crystal. But this accelerator already gets too hot to touch even at its natural 66Mhz clock. To do this safely I would need to attach a heatsink, preferably with a fan on it.

😀

A fan blowing across the chip will do you more good than a small passive heatsink.

Why that? I put a heatsink with glue on the chip. works great.

Warlord wrote on 2021-08-26, 06:49:

heres a crazy thought. Since the cards were designed to be able to run without a heat sink, why then would just normal adhesive thermal tape to hold a small heat sink on not me way more than adequate. even the cheapest 3w tape would be more than enough. There is 12w tape which would be overkill.

Agreed.

I'm not at all panicky about modding old cards - these things are unusual but not Voodoo5-6000 level rare. If someone does his homework and makes as sure as possible not to brick the non-unique hardware, I'd say you go girl. I regularly grab my soldering iron too on my old stuff (usually relocating or more often re-orienting headers, or removing key pins so connectors can fit).

But no point in taking risks if there's little to no potential benefit.

Some physics here: this is all about thermal dissipation. I'm not able to find datasheets for the PCX2 with thermals, but the N64 Reality Coprocessor was made by NEC on the same process at the same time, with just over twice the number of transistors. That chip runs at 62.5MHz and dissipates 2.8W, so it's reasonable to assume 1.4W for the PCX2 at 66MHz. Power consumption scales roughly linearly with frequency, so even assuming a 50% overclock we're not going over 2.1W here. Of course, if you increase voltage, consumption increases with square of voltage, but even with a 10% overvolt it wouldn't get over 2.54W. 10% is already 3.6V, anything over that for a 3.3V part is chip-roastingly unrealistic.

By comparison, the later - more powerful - Riva128 burnt 4W and was frequently shipped without heatsink, and when one was added, it was one like this:

3W tape combined with pretty much any small heatsink should be more than fine to dissipate whatever overclock and overvolt you try with this beast.