Hi! I'm really close to finishing my dream Win98/WinXP dual boot build. Here are the current specs:

MB: ASRock 4CoreDual-VSTA
PSU: Corsair VX550
RAM: 4GB DDR2
CPU: Core2Duo E7600
SND: Audigy 2ZS
AGP - Sapphire Radeon 9600 XT
PCIe - PowerColor Radeon HD 5870 PCS+

I was amazed when I found out that the 9600 XT can output 160Hz at all resolutions I care about (1024x768 and under). I'm using a LogiLink DVI to HDMI adapter, and then HDMI cable to my Gigabyte M32Q monitor. Everything is incredibly smooth and responsive, in Windows and in games as well. I was able to get the same output and refresh rates in XP, but the performance isn't enough for 2003-2010 games with the 9600 XT.

That's where the PCIe GPU comes in - I chose the 5870 for its performance, and my mobo can only take PCI 2.0. I've installed Catalyst 9.10 and after a bit of fiddling to disable the 9600 XT in device manager, everything seems to work just fine under Windows XP with the 5870, performance is as expected.

However - I can only select 75Hz for 4:3 resolutions, and 60Hz for 16:9. This is with the same DVI to HDMI setup as before.
As a result, a few possibilities arise which I can't seem to find the answers for:
- Limitation of the Catalyst 9.10 drivers?
- Limitation of the HD5870? This Guru3D thread seems to mention 5xxx series doesn't support higher refresh rates, but I can't find any other source for that.
- Should I be going with an NVIDIA GPU for my PCIe GPU, are their drivers better for high refresh rate output?

It occurred to me that another option might be to use a GPU that is supported by the latest Omega XP drivers (Catalyst 7.12). I think the most performant one would be the HD3870. It would however be a huge performance downgrade compared to the 5870, so I am not sure that I want to attempt this route.

Thanks for any hints!