[SOLVED] ASUS Prime B350-Plus not detecting PCIEx16 Graphics Cards

Aug 15, 2022
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Hello People, i hope that here is someone that can help solving or at least explain me the problem i have with the computer i am building.

These are all used parts, nothing new. Proven working as they should, but not in this exact combination.

I am using the above mentioned Mainboard ASUS Prime B350 Plus. The Processor i want to use is an AMD Ryzen 7 2700X. I assembled the Computer with this CPU, RAM, and a Palit GTX 780 GPU in the PCIE Slot 1 of the Board and had no video output. I tried two other Graphics Cards, Gainward Phantom 760 and one very old passive cooled one i dont know the brand of yet, still no video output.

thinking that the UEFI version was too old for the board to detect the cpu and lacking the possibility to flash without cpu, i had to buy the cheapest compatible CPU for this board, amd athlon x4 950. with this, the computer worked and i was able to update the uefi to version 5606. the most recent version seems to have issues in the downloaded file ("not a proper bios" error message when trying to flash) so i chose this as the most recent for me. the palit gtx 780 gpu was still in pciex16 slot 1 and worked.

after flashing, i changed the cpu to the ryzen 7 2700x. nothing else changed, just the cpu. but: no video output from the palit gpu. changed to the gainward one, no video output. changed to the passive one, had video output.

when checking the manual of the board i found out that when using a ryzen cpu, it shares another ICQ (G) with the pciex16 slot 1 than the athlon does (D). there doesnt seem to be any option in uefi for me to change this.

in addition, the maximum pcie operating mode for the athlon is 8x while for the ryzen it is 16x. the passive gpu seems to never go faster than 4x since it works regardless of which cpu or slot is used. the other gpus (palit and gainward) seem to demand 16x in the first slot when the ryzen is inserted, which does not work. when i plug them into the pciex16 second slot, they work, but that slot is topped to 4x pcie speed with the only option to change it to 2x.

my friend, whose parts these are, uses the same board and the same processor. the only other thing is the cpu: it is a much newer nvidia rtx 2070.

my conclusion here is, that these old graphics cards are just not made to work in a board with such a modern cpu. i will ask my friend to come over and bring his graphics card with him. if that works, it seems proven to me that these older cards cannot work in that board with that processor.

am i correct with my conclusion or am i missing something?
 
ok, i get it that the GTX 560 does not support UEFI booting. CSM mode is enabled. This one does work but i cannot check the speed of the X16 slot.
the GTX 760 and 770 are said to have UEFI support. they are detected when using the athlon but not when using the ryzen.
maybe because with the athlon the whole pc is in non-uefi-mode.
maybe because they are connected using pcie2.0 instead of 3.0.
maybe because they are connected using x8 instead of x16.
maybe because of the IRQ that is shared with the slot.

my friend uses the same board and ryzen processor. he puts in those cards and they work.

i'm going to work on this today, will keep you updated.
PCIe is forward and backwords compatible. That means the device and the host (GPU and motherboard/CPU/chipset in your case) will negotiate the highest bandwidth and generation that both supports so there should be no issues putting gen 3 device in a gen 2 socket...a 16 lane device in a 4 lane wired socket...and any other odd-ball combination you can imagine. And the other way around too.

That is, of course, if both are working correctly. I'd be more willing to suspect the GPU now if one (even an old one) works and another doesn't. If you can get into BIOS with the one card there are usually some settings to configure how a card slot is to function: you may be able to force them to function in Gen 2 only, or Gen 1.5, 1 even, maybe even force 4 lanes. Then test the other card to see if it will work.

If you can get into Windows then GPUz will tell you how many lanes and what gen the GPU is functioning with. Older GPU's often function with reduced lanes and/or at an older generation for lower energy useage until it's put into 3D mode.
 
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Aug 15, 2022
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i found a pc beeper. it gives the code long-short-short-short when the ryzen is in use and no code when the radeon is in use. according to asus, this can occur on problems with graphics card or cpu current. with the radeon topping to 8x speed can it be that some of the contacts on cpu or gpu are bad so it just fails when trying 16x? how can i test that and what can i do?
 
Make sure your monitor is connected to the GPU and not connectors on the motherboard.

What version precisely did you flash the BIOS to? Reset CMOS with the 2700X CPU in place and do it by both pulling the battery for ~30min's and shorting the reset pins.

You can put the GPU in either of the x16 slots and it should work, although only the top x16 slot will provide full bandwidth since the bottom slots are wired for x4 and gen 2.
 
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Aug 15, 2022
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hi, thanks for the reply

precise version the bios is flashed to right now is 5606, released 2020/07/31

bios has been reset several times but i will try your suggestion as well.

i know that i can put the gpu in the second x16 slot, there they do work but the cause that they wont get the full bandwith is why i try to find out why it doesnt work. as it should - i'm up to cleaning the x16 ports with some contact spray and check the processor pins as well.

will keep you updated.
 
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i know that i can put the gpu in the second x16 slot, there they do work but the cause that they wont get the full bandwith is why i try to find out why it doesnt work. as it should - i'm up to cleaning the x16 ports with some contact spray and check the processor pins as well.

will keep you updated.
It's important to reset CMOS after any hardware swap. Doing it with the desired hardware in place is just a good way to make sure it's been done.

Yes, if the GPU works in other sockets then the CPU may have faulty I/O circuitry that connects to the top, x16 socket. The problem could be in the CPU socket too. You have to be careful as poking around at those delicate contacts (in CPU, CPU socket or PCIe socket) can damage some that aren't bent or broken.
 
Aug 15, 2022
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CMOS was reset. there is another gpu i found that is working: asus gtx 560. difference to the two other gpu is that the gtx 560 is pcie16 2.0 instead of 3.0. when booting the computer after cmos reset, the bios told me that the connected gpu was not uefi compatible. for me it now seems there is some compatibility stuff happening with the other two gpus (760/770)?

what the heck is happening here. uefi not able to detect uefi graphics card? but why do those cards work when using the athlon cpu.
 
CMOS was reset. there is another gpu i found that is working: asus gtx 560. difference to the two other gpu is that the gtx 560 is pcie16 2.0 instead of 3.0. when booting the computer after cmos reset, the bios told me that the connected gpu was not uefi compatible. for me it now seems there is some compatibility stuff happening with the other two gpus (760/770)?

what the heck is happening here. uefi not able to detect uefi graphics card? but why do those cards work when using the athlon cpu.
I think all that means is you can't use UEFI mode of operation with a GPU that's not UEFI compatible, it should work with legacy or CSM (Compatibility Support Mode).

I think it has to do with how the motherboard's BIOS hands-off the GPU initialization to the GPU's BIOS during boot-up. UEFI does it in a much more secure fashion that's hard for a virus or trojan to exploit. CSM mode should make the UEFI firmware on the motherboard act just like an old-fashioned BIOS would.

Older GPU's aren't UEFI compatible and you are dealing with some pretty old ones.
 
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Aug 15, 2022
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ok, i get it that the GTX 560 does not support UEFI booting. CSM mode is enabled. This one does work but i cannot check the speed of the X16 slot.
the GTX 760 and 770 are said to have UEFI support. they are detected when using the athlon but not when using the ryzen.
maybe because with the athlon the whole pc is in non-uefi-mode.
maybe because they are connected using pcie2.0 instead of 3.0.
maybe because they are connected using x8 instead of x16.
maybe because of the IRQ that is shared with the slot.

my friend uses the same board and ryzen processor. he puts in those cards and they work.

i'm going to work on this today, will keep you updated.
 
ok, i get it that the GTX 560 does not support UEFI booting. CSM mode is enabled. This one does work but i cannot check the speed of the X16 slot.
the GTX 760 and 770 are said to have UEFI support. they are detected when using the athlon but not when using the ryzen.
maybe because with the athlon the whole pc is in non-uefi-mode.
maybe because they are connected using pcie2.0 instead of 3.0.
maybe because they are connected using x8 instead of x16.
maybe because of the IRQ that is shared with the slot.

my friend uses the same board and ryzen processor. he puts in those cards and they work.

i'm going to work on this today, will keep you updated.
PCIe is forward and backwords compatible. That means the device and the host (GPU and motherboard/CPU/chipset in your case) will negotiate the highest bandwidth and generation that both supports so there should be no issues putting gen 3 device in a gen 2 socket...a 16 lane device in a 4 lane wired socket...and any other odd-ball combination you can imagine. And the other way around too.

That is, of course, if both are working correctly. I'd be more willing to suspect the GPU now if one (even an old one) works and another doesn't. If you can get into BIOS with the one card there are usually some settings to configure how a card slot is to function: you may be able to force them to function in Gen 2 only, or Gen 1.5, 1 even, maybe even force 4 lanes. Then test the other card to see if it will work.

If you can get into Windows then GPUz will tell you how many lanes and what gen the GPU is functioning with. Older GPU's often function with reduced lanes and/or at an older generation for lower energy useage until it's put into 3D mode.
 
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Aug 15, 2022
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too bad this board has no way to configure anything regarding the pciex16_1 slot. i can configure the pciex16_2 slot to be 2x or 4x.

i will use the gtx560 in the primary slot to install windows and when the computer goes back to my friend he will check with his rtx2070 that works in his computer with the same brand and model of mobo, cpu and psu. if that does not work, the board must have some kind of defect.
 
Aug 15, 2022
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i have decided to go with the GTX560. my friend will test his gpu. if it works, okay. if not, a new board is bought. thanks for your help, even if the problem is not finally solved (which most likely is not possible as it seems) this thread might help someone else.
 

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