The clock frequency of the Voodoo Graphics is set via environment variables in DOS. The stock frequency (probably via drivers) is 50MHz. Use 'SET SST_GRXCLK=53' to set it to 53MHz for example 😀. See Voodoo Environment Variables for more variables.

Cards with the same PCB and different arrangement of strap resistors show different performance. For example, Voodoo1 Real Vision Flash - 1550 3DMark99, and ColorMAX VP-503 - 1230 3DMark99. Chip heating on Voodoo1 Real Vision Flash is 65°C, and ColorMAX VP-503 - 47°C. We can assume that they work at different frequencies set by the manufacturer of strap resistors. But how can we find out the value of this frequency? My oscilloscope does not allow making precise measurements. Perhaps there is a program that does this?

After installing resistors on ColorMAX VP-503, like on Voodoo1 Real Vision Flash, it also shows 1550 3DMark99 and the chips started to heat up a lot. All this happens under the same conditions, on a P2B/Pentium III-500 motherboard

It seems that the straps hanging on the FBI pins 109, 110, and 111 set the operating frequency. 010 is the standard 50 MHz. I came across the combination 000 - this is significantly lower, like 35-40 MHz.

It’s not that all of this was absolutely necessary, but once you start looking at configuration strap resistors, it's hard to stop:)))
Perhaps someone will find this information about Voodoo2 cards useful. It may be useful if you want to make friends with two different cards under DOS in SLI mode

Strap resistors that set the frequency and board ID on the Volcano 3DX2000

Strap resistors that set the frequency and board ID on the InnoVision Mighty 3DII V3

Strap resistors that set the frequency and board ID on the Creative 3D Blaster Voodoo 2 CT6670

Not got the software to hand to do an overlay as above, but here is the Maxi Gamer 3D²

paradigital wrote on 2025-05-12, 19:04:

Not got the software to hand to do an overlay as above, but here is the Maxi Gamer 3D²

The attachment IMG_4996.jpeg is no longer available

Thanks for the photo, I don't have such a board. You can see the default location of the strap resistors. "Board target 3D clock: 90 MHz", board ID - "generic Voodoo2 board".
Further operation of the board will be set by drivers (environment variables DOS+glide2x.ovl, or drivers in Windows)

I don't know the manufacturer of this Voodoo1, but clock_default=42MHz

After setting 'SET SST_GRXCLK=50', DOS and Windows programs that use Glide instructions read this variable and set clock=50MHz, and when finished, set clock=30MHz.

Windows programs that use DirectX instructions ignore the 'SET SST_GRXCLK=50' variable, read the strap resistor configuration and set clock_default=42MHz

Interesting, thank you for the research 😀

I plan to do some Voodoo1/2 benchmarks and this is very important thing to keep an eye on. So in D3D on Voodoo1 the frequency is configured by the strap resistors and there is no way to change it in SW? How about V2, does it behave the same?

Postman5 wrote on 2025-05-18, 13:09:

Windows programs that use DirectX instructions ignore the 'SET SST_GRXCLK=50' variable, read the strap resistor configuration and set clock_default=42MHz

Where exactly on the PCB did you measure the frequency?
I have a Voodoo 1 board based on the same design and would like to test it myself.

zyga64 wrote on 2025-05-19, 08:50:

Postman5 wrote on 2025-05-18, 13:09:

Windows programs that use DirectX instructions ignore the 'SET SST_GRXCLK=50' variable, read the strap resistor configuration and set clock_default=42MHz

Where exactly on the PCB did you measure the frequency?
I have a Voodoo 1 board based on the same design and would like to test it myself.

I connected to the 11th pin of the DAC, through an attenuator ~ 1:10

havli wrote on 2025-05-19, 08:14:

Interesting, thank you for the research 😀

I plan to do some Voodoo1/2 benchmarks and this is very important thing to keep an eye on. So in D3D on Voodoo1 the frequency is configured by the strap resistors and there is no way to change it in SW? How about V2, does it behave the same?

I'm getting ready to explore Voodoo2. What does the abbreviation "SW" mean?

I meant if there is a way to set frequency for D3D by software tools - the environment variables or some application.
If "SET SST_GRXCLK=50" doesn't work for D3D, is there something that does?

havli wrote on 2025-05-19, 10:39:

I meant if there is a way to set frequency for D3D by software tools - the environment variables or some application.
If "SET SST_GRXCLK=50" doesn't work for D3D, is there something that does?

For Voodoo2 there is "Voodoo2 Overclocker V1.5", it allows changing the frequency within 50-120MHz. But I have not looked at how it affects DirectX applications. For Voodoo1, there are no similar applications, it seems.

Thank you !

I think that Powerstrip is able to overclock Voodoo 1 (and underclock a little - to 48 MHz). It stores clock value somewhere, which is applied when Windows is restarted, even if Powestrip isn't configured to launch itself at startup.
Everest Home edition can display 3dfx frequency (and it changes immediately when over/under clocked with Powerstrip). My voodoo 1 shows artifacts with default 50MHz clock (in D3D and Opengl applications - for Glide I can downclock it by SST_GRXCLK variable), while it doesn't when downclocked to 48MHz.
I think it may be due to the memory used, because I soldered "35ns" chips bought on AliExpress. I can't confirm that it's really 35ns...

On Voodoo1 Diamond the clock is set by strap resistors to 50MHz, and in all applications this clock is the same. When exiting applications with DirectX instructions the frequency does not decrease to 30MHZ, but remains equal to 50MHz. The connection point of the attenuator on Voodoo1 Diamond is also 11 pin of DAC, but it is more convenient to connect to the connection between resistors R61-R60-R25