vBIOS for AGP DX11 core-swap

[Khenglish]

I decided to try out soldering an HD 6570 core onto an AGP HD 4670 in attempt to make the world's only DX11 AGP card because the 6570 was only $20, and I had the tools for it so why not. The surgery went well, but very unsurprisingly the card is not happy with either the 4670 or 6570 vbios.



4670 vBIOS:
Card is fully powered on. Core and vRAM voltage are confirmed as correct.
POST with blank screen.
GPU initially turns on but quickly stops. This implies the GPU crashed during initialization (makes sense with the wrong core vBIOS code).

6570 vBIOS:
Card is fully powered on. Core and vRAM voltage are confirmed as correct.
No POST. I think the uninitialized AGP is fighting with the mobo and causing an overcurrent situation.
GPU fan runs. This implies the card at least internally completed its startup.


I don't know of anywhere else with more experienced AMD/ATI bios modders, so I posted here in hopes that one of you would happen to have the knowledge to create a vBIOS for this monstrosity so that AGP can finally make its long overdue jump to DX11. I think the card would work if it had a custom vBIOS. It powers up and is reading the vBIOS chip, which indicates that the core is in fact electrically compatible with the pcb. I think it should work with either 6570 core code injected into the 4670 vBIOS, or an AGP section added to the 6570 vBIOS. I looked at a PCI-e 4670 vbios and it looked very different so nothing stood out to me as a simple change for AGP support. Both the 6570 and 4670 PCBs are very similar, with the major difference being the PCIe-AGP bridge chip. vbios dumps are attached with the extension changed to .txt for allow for upload.

 

[Khenglish]

The 4670 core will be going back on soon without some vbios magic ideas. @W1zzard @Diverge @VuurVOS

I totally understand if it would be too much work though. I figured I'd give it a shot for laughs.

 

[W1zzard]

Gddr3 vs gddr5? The aint gonna work

 

[Khenglish]

Both cards use 16 bit DDR3 modules. RAM is correctly powering up to 1.6V.

Your are correct that GDDR3 and GDDR5 cores are electrically incompatible. RAM is shorted and can't power on when attempted.

 

[Steve-007UK]

@Khenglish This was an interesting thing to try and thank you for having a go even if it worked or not

It got me thinking tho because i recently seen the reverse engineered 3dFX Voodoo 6000 card.

Not sure if this has been tried before but if you or anyone else can pull it off rather than trying to swap the GPU die how about making a custom PCI or PCIe to AGP convertor riser cable/card thing.

 

[Khenglish]

@Khenglish This was an interesting thing to try and thank you for having a go even if it worked or not

It got me thinking tho because i recently seen the reverse engineered 3dFX Voodoo 6000 card.

Not sure if this has been tried before but if you or anyone else can pull it off rather than trying to swap the GPU die how about making a custom PCI or PCIe to AGP convertor riser cable/card thing.

That in essence is what the AGP-PCIe bridge chip is. I'm sure that could work, just a lot of design work and it won't be cheap. The bridge die is a custom ASIC with a substantial transistor count.

 

[Khenglish]

Well with the lack of interest in this mod I put the 4670 core back on and it works fine.

With just cap mods I increased the core max overclock from 840 to 910 MHz at stock 1.3V. There are major issues with the RAM voltage supply that I am trying to fix, where adding RAM caps makes the RAM voltage unstable. This thing is far more limited by RAM clocks than core clocks.