VOGONS


First post, by Kahenraz

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I've been reading about people having good success overclocking their Matrox M3D PowerVR PCX2 due to its standard crystal and built-in clock adjustment in the AV7-05 PLL Frequency Generator. The issue I'm having is that I want to overclock a card using Videologic's reference design which has a quartz crystal clocked at 66Mhz with no PLL chip.

I found information about this specific clock chip from the manufacturer as well as the datasheet.

I also found what appears to be a drop-in replacement 80 Mhz crystal.

Does anyone have any previous experience modifying this particular card? I'm also interested in trying other frequencies if there are other compatible crystals available.

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This board will also accept a larger crystal if necessary without the need for additional modifications.

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Here is an Matrox M3D for reference for anyone who wants to see how these boards differ.

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Here the source I used for my research for anyone looking for modify their Matrox M3D:

https://web.archive.org/web/20100113010840/ht … /tfaq/tfaq.html

Last edited by Kahenraz on 2021-09-07, 12:29. Edited 2 times in total.

Reply 2 of 47, by Kahenraz

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I also have the option to modify a board with either IBM or NEC memory. I don't know which would be more accommodating to an overclock.

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386SX wrote on 2021-09-07, 11:40:

I never overclocked those cards considering how rare they are and how much they already heat up. 😉

I will be careful and I will also be adding a heatsink and a fan to compensate for the added heat.

386SX wrote on 2021-09-07, 11:40:

I own a m3D Rev.C myself.

I have several different revisions of the reference Videologic Apocalypse 3DX and two Matrox Rev. B. I've read that the Rev. A is supposed to be easier to overclock but this may be anectdotal.

Last edited by Kahenraz on 2021-09-07, 12:06. Edited 1 time in total.

Reply 3 of 47, by janskjaer

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Pardon my somewhat cautious approach, but may I ask why you are wanting to overclock a PCX2?
What is it that you are looking to achieve?

Of course, it is your hardware, and you are free to do what you wish with it.
But, given the increasing rarity of such cards, does the purpose of your efforts outweigh the risks of damaging the board?

I would advise you to consider the following questions, before commencing with any overclocking modifications:
- What am I looking to achieve from this?
- What will the overclocking attempt enable me to do, that the card cannot already do?
- What are the risks of damaging the card?
- How valuable to me are the results of my work and to the rest of the community (after all, I presume that is why you're posting here).

Please remember that, ultimately, the card will be limited in what it can do (e.g. which games it can run well with). We must be realistic about this.
I don't want to dampen your passion for retro hardware or optimism for optimising (pun intended), but consider please consider this food for thought.

DELL Dimension XPS M200s
:Intel P1 MMX 200MHz
:64MB RAM
:DOS 6.22/Win95b
:Matrox Millenium II PCI
:Matrox m3D (PowerVR PCX2)
Chaintech 7VJL Apogee
:AMD AthlonXP 2700+
:3GB RAM
:Win98SE/Win2000 SP4
:3dfx Voodoo5 5500 AGP

Reply 4 of 47, by Kahenraz

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janskjaer wrote on 2021-09-07, 12:04:

Pardon my somewhat cautious approach, but may I ask why you are wanting to overclock a PCX2?

Because it's a very simply modification that is also easy to reverse. I am willing to take this risk to learn more about the limits of this very interesting piece of hardware.

janskjaer wrote on 2021-09-07, 12:04:

But, given the increasing rarity of such cards, does the purpose of your efforts outweigh the risks of damaging the board?

I have a lot of experience with this kind of rework. There is very little risk. Look up some of my other threads where I talk a bout my repair work. I've done far more complex projects than this.

I already have a PowerVR PCX2 ready to go under the iron for repair. So it's not like I would need to modify an already working card if that is what I decide.

Reply 5 of 47, by keropi

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I have seen on ebay a newly-made combo card: virgeDX + 66/80mhz PCX2 so at least PCX2 works at 80mhz
since you have the means go for it

🎵 🎧 PCMIDI MPU , Orpheus , Action Rewind , Megacard and MK8330 soundcard website

Reply 6 of 47, by BitWrangler

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It occurs to me that 66 Might have been chosen for PCI bus synchronization, since it's gotta push data to the 2D pixel shover. Obviously it has to cope with systems with different FSB and PCI speeds, but I'm thinking it might not result in higher frames per sec on a normal 33mhz PCI bus. Possibly though if you matched to FSB frequency and PCI is not locked to 33, then 75 or 83 Mhz crystals might give good results when run on 75/2 and 83/2 PCI.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 7 of 47, by Kahenraz

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That's an interesting idea to match the PCX2 clock with an overclocked FSB.

The motherboard I'm pairing it with supports 50, 60, 66, 75, and 83 Mhz FSB clocks. The best I can find is an 80 Mhz crystal.

Reply 8 of 47, by Kahenraz

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Oh, no! How did this happen?

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I found this. Maybe it fell out all by itself.

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Reply 9 of 47, by BitWrangler

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Xfiles stuff, maybe some bipedal life form poked at it with a hot stick.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 10 of 47, by Kahenraz

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I added a through-hole socket so now I can easily swap in and out different crystals to find the perfect clock before soldering in the final value. very convenient. 😀

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Reply 11 of 47, by Kahenraz

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I've ordered a couple of 80 Mhz crystal oscillators today for this project. I wasn't able to find any value between 66 and 80 Mhz that was pin-compatible. I did find some 90 and 96 Mhz crystals but they were expensive and the PCX2 might not even be stable at that speed.

I'll follow-up on this some time next week. I also have lots of different heatsinks on order to try out.

Reply 12 of 47, by Kahenraz

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I swapped in a 80Mhz crystal today and it worked great!

I tested this very briefly with Tomb Raider by launching the game and letting the demo run for a few seconds. The chip gets extremely hot and I would not recommend doing this mod without adding a heatsink.

5V can be gotten from the top left pin where a larger crystal would fit. This can be used to power a small fan.

I don't know of a good way to benchmark this though. I don't think there are any PowerVR games that also have a frame counter.

Reply 15 of 47, by BitWrangler

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The trick back in the day was to cut thermal epoxy with thermal compound, so it weakened it enough to be able to get the sink off if required, but still hold well in regular use.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 16 of 47, by Kahenraz

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Thermal tape or even regular double sided 3M that appears pre-applied on a lot of heatsink kits. The question is how well they will provide thermal conductivity.

I don't think you can beat thermal paste with any adhesive but I don't see a good way to attach a heatsink without drilling holes. Drilling holes without knowing what's in the PCB is dangerous and a fire hazard. I would be willing to drill into one of mine if I can get it x-rayed first for safety.

Reply 17 of 47, by leileilol

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Kahenraz wrote on 2021-09-22, 17:49:

I don't know of a good way to benchmark this though. I don't think there are any PowerVR games that also have a frame counter.

Omega Field from the PC3DEngine disc's got a counter
The original Unreal versions with a working SGLDrv should still have the timedemo statistics
(retail) Turok's got a benchmark

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