Checking those arcade schematics is just brilliant, it never occured to me, thank you!
This will prove quite useful if I ever decide to do with the OG Voodoo chipset what I'm doing with the V2, saves countless hours of sanding the pcb, scanning, retracing and getting a schematic.

As for the V2 TMU, I randomly compared about 30 pins, and they are identical to the
500-0004-02. I'll check all the pins and give an update later today.
Edit: All V2 TMU (500-0010-01) pins are identical to the V1 TMU (500-0004-02). This could prove to be quite interesting...

Regarding the TT bus, you are right.
A V2 looks like this:
FBI to TMU0 and FBI to TMU1 (same nets but the bus is split), this is the FT bus.
TT bus (from TMU1 to TMU0)
FT bus (from TMU0 to FBI).

Basically the TMU outputs are daisy chained back to FBI input.

Wow, thank you for checking that, that's amazing that the pinout is the same 😀
That's quite interesting that the TT bus is potentially just used to send the TMU's data back to the frame buffer and the FT bus is shared - that must be why there are FT address pins, to address data to each of the TMUs?

I've now done the same treatment for the 3Dfx 500-0003-03 FBI chip. This one's a bit different in how it addresses memory, there are only two sets of memory addressing pins and the notation for the framebuffer memory data pins doesn't clarify which set of FB_DATA pins goes to which memory chip. So I've clarified the picture with a colour highlight for each memory chip - the boxes with two colours are the pins shared between two memory chips.

Here's the colourised version:

And the unannotated version:

They're losslessly compressed this time 😀
Unfortunately this is where the Voodoo 1 differs from the Voodoo2 - the 500-0003-03 FBI chip has 240 pins while the 500-0009-01 CK or 'Chuck' has 256 in total. I do wonder if the pins would be the same up to pin 240 and then they added in some extra pins, or if it's all different.

Yes, you're right, that's why the FT has address pins. Each TMU has a few config resistors (hanging on the RAM bus, address pins if I recall correctly), that's how the TMU address is set, among other things.

In a day or two I'll post a delta between the two FBI ICs.
Btw, the OG Voodoo Graphics can have up to 3 TMUs and supports SLI, eg. Primary Image Pirahna IIRC.(if it's not that it's the Barracuda, although I think that uses the V2 chipset).

I compared the pinouts, the V2 FBI has the following extra pins:
- 2 extra RAS lines
- PCI INT pin
- SLI SYNC signals (2x)
- a reset signal that goes to the TMUs (buffered from PCI RST)
- a clock signal that goes to the SLI slave
- a pin for sensing if the card has a monitor plugged in, goes to the RAMDAC which detects the 75R VGA terminations (this is how 1 card becomes the master in an SLI setup).

If you give me a potential pinout I can make an initial pinout picture for you 😀 Just 16 pins between the two

I am trying to figure out why my Orchid Righteous 3D only sees 1MB on the TMU when I can't see any bad pins. I am wondering if perhaps I reconfigured one of the strap resistors - I did most of the work on this faulty card in 2021-ish, before I kept reliable logs of changes I make to each item.

Those additions for SLI / function make sense, as far as I'm aware the 3Dfx FBI chip has little the in way of GPIO type pins to assign extra functions to. Makes Anthony's King Shaman 3Dfx Voodoo 1 card quite impressive at a hardware level 😀

Wow, 18 months ago I forgot I made this picture when I was first troubleshooting my £20 trainwreck Voodoo 1 reference design card:

This is from the PI5C-3384Q datasheet since that's one of the first parts I was fixing. Should be the same on most designs that use this small 24-pin chip to switch between the two VGA sources like a KVM 😀

Most Voodoo 1 cards use resistors and resistor packs to connect up the memory data / address / RAS / CAS lines and if you've watched any 3Dfx repair videos you'll know those can be at fault too. I was trying to figure out what caused the black blocks on textures on my reference Voodoo 1 and through chance tracked it to the one resistor pack that connects up TMU memory on this cheaply made card (nicer cards will use resistor packs for everything):
Re: What retro activity did you get up to today?
One solder joint went bad on this resistor pack, which connected up the CAS (column address select) lines to the TMU memory chips, which broke the cards ability to put data into all of the texture memory even though all the RAM was good.

For troubleshooting memory issues I think it's probably best to start with checking that the RAS & CAS lines are still working. I've made this A4 sized colour printable version of the pinouts which includes the EDO RAM pinout too.
Instead of just checking from each side of the resistor pack, it's best to check from RAM pin to TMU / FBI chip pin, since applying pressure to the resistor pack might make it make a normal connection again.

Thanks for this information.
I had some success repairing my Diamond Monster card earlier this year. There is software You can check the Ram chips but need a PCI card that has expansion slots.

3dfx Voodoo 1 fault diagnosis and repair

I still have a friends card to repair and all RAM chips tested ok. I'll take a closer look at the resistor packs.

Imperious wrote on 2023-11-22, 00:30:

Thanks for this information. I had some success repairing my Diamond Monster card earlier this year. There is software You can […]
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Thanks for this information.
I had some success repairing my Diamond Monster card earlier this year. There is software You can check the Ram chips but need a PCI card that has expansion slots.

3dfx Voodoo 1 fault diagnosis and repair

I still have a friends card to repair and all RAM chips tested ok. I'll take a closer look at the resistor packs.

Ah, your thread inspired me to keep going, thank you for sharing it! 😀
That thread is a great example of what an FBI / frame buffer memory failure looks like - very different from a TMU failure since texture memory doesn't affect overlay like that it, it only affects textures,