Bios Mods -The Best BIOS Update and Modification Source

So, I've got a couple of virtualization lab servers, built on Tyan S3992 boards (of which I'd like to run Istanbul 6-Core CPUs, but no-one seems to be interested in replying to my thread in the CPU unlocking section), that I'm currently trying to mess around with RemoteFX and VDI (Hyper-V, Server 2012).

Tyan's website suggests that the PCIe slots cannot be used for video cards, however I know this to be false, as I can happily run my Radeon HD 6450 in either of the two 16x (16x physical, they are only 8x in reality) slots. When I try to use an nVidia card though, the board fails to boot to POST.

I have no idea if this is something which is unlockable or not, but if it is possible, I'd like to be able to use either my GTX 295 or GTX 480 in the board, so as to get me a bit better performance than the rather paltry AMD cards I have lying around (5450s and 6450s). Can anyone shed some light on why I can't boot from an nVidia card? Is it possible to unlock the ability to do so? I'm guessing the reason I can boot from an AMD card is that the motherboard has an onboard ATi ES1000 video chip, so it's expecting an ATI/AMD video BIOS?

The latest S3992 BIOS files can be found here.

Any help appreciated (either in this thread, or the request I made in CPU unlocking: here)

One more thing, is it possible to allow AMD Nested Pages (SLAT)?

Just found this forum, I have no BIOS-modding experience, but I do have a S3992 and decided to run some tests. I also assumed no graphics card would work because of the product specification. I can't fit a GPU in PCI-E1 (CPU1 heatsink in the way) but I tried a Sapphire GTX580 and HD7970 in PCI-E2.

Results:
GTX580 works, but only at 1600x1200. I don't know if it's because the driver doesn't like server 2008 (vista driver, no official support)
HD7970 works at native (2560x1600) with catalyst drivers.

Windows 8 doesn't boot at all regardless which GPU I'm using, not sure why that is.

I'm on BIOS 1.04, haven't updated yet, but will definitely get the modded BIOS and some new CPUs
The fastest model currently working with the modified bios would be 2389 right? Which CPU(s) have you tested?

Let me know if there's some specific test you want me to run on either card.

Hey, cheers for the input.

I can't get any nvidia cards to boot at all, not sure if it's a problem with other add-in cards or option-roms that are running, but all ATI/AMD cards tried work flawlessly.

As for CPUs, I've got a pair of 2356's right now, but really want someone to reply to my CPU unlocking thread so I can go dual hex-core. I've got two sat there waiting for me (2419), but no go so far