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Bios vs UEFI in GPU's. (GPU Guru input needed!)

AntDeek

AntDeek

Joined
Aug 4, 2016
Messages
340 (0.11/day)
System Specs
Processor 8700k OC @ 5GHz (1.35 V)
Motherboard ASUS Prime Z390-A
Cooling Corsair H100i v2
Memory 16GB DDR4 OC @ 3000MHz
Video Card(s) EVGA RTX 2070 XC Ultra
Storage 4 x 250GB PNY SSD & WD BLACK 1TB HDD
Display(s) Samsung UHD 4K / BenQ RL2455HM
Case NZXT H500i
Power Supply Corsair 750W
Software Windows 10 Pro
So I am having some strange behavior with my PC. My PC does not support UEFI boot over SATA, so I am stuck with legacy bios. Not a big deal.

Behavior as follows:

With BIOS set to "Video Option ROM = UEFI" I never get the Windows 10 boot up screen, I just get a glitched screen until the Login Screen appears. It seems that I get no video until a driver is loaded when windows loads.

With BIOS set to "Video Option ROM = Legacy" I see the normal windows 10 boot screen the whole time.

With my new GTX 950 coming soon, will I see any performance degradation while running the card in legacy option ROM as opposed to UEFI?

In short, with UEFI mode on I only get output when windows loads, but with legacy, I get output while the computer boots as well.

Thank you!
 
UEFI does not have much/anything to do with SATA. UEFI requires GUID Partition Table though which means you need a clean operating system installation to switch to it.

Video card firmware must support UEFI. If it does not and the motherboard is running in UEFI mode, the video card will only output a black screen.

UEFI is better than legacy (much faster).
 
The only thing UEFI gives you is a sightly faster boot, after you have booted into Windows there is no difference between UEFI and legacy, no need to worry.
 
Last edited:
I see, thank you. Actually, My mobo can boot UEFI over USB, but not over internal drives oddly enough.

So, the reason why I get a black screen until windows loads when the Video Option ROM is in UEFI mode is because windows loaded drivers?
 
It is probably because the motherboards bios cannot talk to the GPU bios during startup, do you have your IGPU enabled?, try connecting your monitor to your IGPU and see if it displays during load.
 
Your listed specs show your Motherboard as Q77, that is the chipset, not the manufacturer or model number of the board.
Most boards of that vintage, (recent) have at least two sata ports for the boot drive to be connected to, and do have UEFI.
Check you have the boot drive connected to the correct port and it is enabled in the BIOS.
 
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