BIOS Shadow RAM question, about graphics cards

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Cody Willis

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Jul 22, 2015
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Say I have an onboard video card, and a PCIE video card, are they always in shadow RAM at address C000, but with different Option ROM data accordingly to the card used?
Like this:
1) If I use my separately bought Radeon video card (mounted inside my computer in a PCIE slot), it will get copied to segment C000 (from the PCIE card to computer's memory).
2) Or, if I didn't install any software driver for my PCIE Radeon video card, then the onboard video card's ROM contents get copied to segment C000.
Please dive into detail with me.
 
Solution
popatim
Drivers happen in windows. Shadowing Rom's happens at the bios level.
With plug n play, devices negotiate address space with the bios, each card gets its own space. You can view this address space in the devices properties in device manager. Which address space they get assigned depends on the order the bios looks for them so if you have GPU to initialize first set to PEG then your pci card gets to pick first. Set to onboard - the integrated gets first grab.
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popatim

popatim

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Drivers happen in windows. Shadowing Rom's happens at the bios level.
With plug n play, devices negotiate address space with the bios, each card gets its own space. You can view this address space in the devices properties in device manager. Which address space they get assigned depends on the order the bios looks for them so if you have GPU to initialize first set to PEG then your pci card gets to pick first. Set to onboard - the integrated gets first grab.
 
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