Asus p5ql-e not recognising asus rog mars gtx 760x2

[moutapt]

Hi everyone, the title says it all, but I'll explain everything.
A couple years ago I had a desktop. I made a new one, and kept the old one in the corner.
I upgraded the graphics card of the new one last year.

So I thought, "I'm gonna put this card in the old desktop and It'll be a second pretty good pc to plug into my living room's tv to play some games."

So I did it. The thing is, the old desktop gives me a bios error. One long beep and three short ones. I looked into it, the code is for vga not detected.

So, here's a short version of what wich pc has, and keep in mind that the new pc, the one thats working still has everything it had when the old card was being used (I probably am making this really confusing, sorry)

old pc:
Motherboard: asus p5ql-e
CPU: Intel core 2 quad q9300 2.5ghz
Ram: 5ghz
Graphics Card: Asus eah3850x2 1g
Psu: 650w

New pc currently
Motherboard: asus m5a99fx pro r2.0
CPU: Amd fx 9590
RAM: 16ghz
Graphics Card: Asus strix gtx 1080 8g
Psu: 860w

Both work in these configurations.

The graphics card that I'm trying to use in the old pc is the one that i took from the new, and its a asus rog mars gtx 760x2.

I've tried putting the 860w psu in the old computer, the error continues.
Tried removing the ram, the error continues.
Tried putting the mars grafics card in the new pc, it works, so the card is good.

I came to the conclusion that there is either an incopmatibility issue that I'm not aware of, or theres some configuration in the bios that needs to be made.
Its either that or the old board is malfunctioning. But if thats the case its weird that it works with old setup.

Can anyone shed some light here? I'm really stuck...

 

[romirez]

Asus rog mars gtx 760x2 is working in SLI mode and will need 16 lines of PCIE.
Check if your old mobo PCIEX16 slot is working at 16x mode. Use GPU-Z program.

 

[moutapt]

I just checked it with the old graphics card and it says "pci express 16x 1.1 @ 16x 1.1" or something like that.
By the way the bios has the latest version installed.
I'm guessing that 1.1 is why it doesnt run? Mobo too old?

 

[romirez]

Is gtx1080 in old comp working well?

 

[moutapt]

I knew I was forgetting something! lol
I'll give it a go tomorrow cause its late here. I'll let you know how it goes once I try it.

If it doesn't work is probably the Mobo, right?

 

[romirez]

May be some incompatibilities with oldies.

 

[moutapt]

Ok, thank you so much for your help, I'll tell you tomorrow if it worked.

 

[moutapt]

Ok, I tested the new graphics card on the old comp and the same thing happens, vga error. So it seems the problem lies with the mobo, compatibility issues probably.
Thank you very much for your help romirez.