riplin wrote on 2025-04-27, 23:30:

I focused on the memory timing stuff and I think I found a "bug" in the G200 BIOSes. It's loading a default timing value that's meant for the G100 card (the value is the same as the G100, but the register has changed and now bits are falling in reserved sections).

Very interesting finding, fix the bug would let the g200 have higher perfomance?

That would really depend on how the values are interpreted by the card. I haven’t gone through the trouble of figuring that out yet. There’s so many interesting things to look at.

The G100 is a close iteration of the Mystique, so you might compare those. The G550 is the remnants of the buried G800, should be close to the G400 but how close? It has a dual texturing pipeline but works with G400 drivers from a year prior.

I was intending to also disassemble the Mystique (not the 220, no data sheet for that one), Millennium and Millennium II BIOSes, but I’m taking a bit of a breather. These things take a long time to disassemble and annotate. Only the PCI version of the G200 was quick because it was so similar to the AGP version.

Edit: I also looked at the G450 BIOS, but it's larger than the G400 BIOS by 2KB + "extra" (BIOS files have to be multiples of 512 bytes and that's reported in the 3rd byte). There's 338 bytes at the end. Also, I don't have the data sheet for the G450 and given that they added DDR memory support to this card, the memory timings are going to be completely different. A large part of that code is going to be: Unknown value written to Unknown register. Not really useful.

I added the Matrox Mystique PCI BIOS disassembly.

I also had a look at the Millennium and Millennium II BIOSes, but the datasheets don't document any of the indirect registers. These contain the PLL setup registers, so kind of flying blind there. 🙁 I also had a look at the Atlas and Athena, but those are very different from the other chips. They emulate older hardware through software. When a Hercules / MDA / CGA register is poked, an interrupt is generated and the BIOS will then see what register was accessed and apply an equivalent change to the VGA registers. brrrrr. 😖 Not touching that.

So I think I'll keep it to the BIOSes I have disassembled right now and annotate those as much as I can. I've already done more work in the G200 BIOS, but I'll have to port those findings over to the other BIOSes. Keeping them all in sync is a lot of work.

Good job! A G100 BIOS modification with proprietary Matrox Simple Interface (MSI) 3D API support (like in Mystique videocards) will be something cool.

riplin wrote on 2025-05-05, 17:27:

I also had a look at the Millennium and Millennium II BIOSes, but the datasheets don't document any of the indirect registers. These contain the PLL setup registers, so kind of flying blind there. 🙁

I was wondering if you also used the sources from the linux fb driver and X window system video driver as possible information sources to further annotate the disassembled code ? If at all usable & possible.

That’s a good idea, I’ll have a look at those.

As for the other bioses, it’s not mainly a lack of documentation that’s hindering me there. It’s a lack of understanding 😀. There’s a lot going on and sometimes functions do things that are seemingly unrelated to each other. Very annoying.