Upgrading a Nvidia card to a Ati card?

[LavCat]

The mapping is being done by the BIOS. You can set the BIOS to not use the video memory as system memory, thus the reasoning behind Video Memory != System Memory. The AGP apeture (yes, I know it's PCI, but they didn't change the name of it) can be set to 0 which means the OS doesn't see the video memory, just the system memory while the video will still happily use it's own memory as needed.

The BIOS of my Asus M4A79T Deluxe has no such option, nor any other option that I can find for graphics card memory mapping. Everything I can find on the web (including a Datth blue Blizzard post, so we know it must be true) indicates the setting does not exist for PCIe. What motherboard are you using?

I don't claim to know a lot about AGP or PCIe but in another life I did design, program, and manufacture PCI cards for computer cameras.

(Datth has solved an intractable video problem for me, so in spite of my humor, I think he/she is probably correct.)

Also, at boot time I am almost certain the video card will look like a good old IBM standard Video Graphics [quote], so the BIOS does not need to know anything else about it.