Sign in with
Sign up | Sign in
Your question

PCIe 3.0 x8 card in PCIe 2.0 x16 slot: will it run in PCIe 2.0 x8 or x16 mode?

Last response: in Graphics & Displays
Share
March 5, 2014 9:06:16 AM

I've seen a number of questions asking similar questions to the above, but I couldn't see that anyone had asked my specific question yet, so here goes.

I'm about to buy a Gigabyte GV-R725O5-2GI PCIe 3.0 x8 video card.

My motherboard has PCIe 2.0 x16 slots.

My question is whether the card will run in PCIe 2.0 x16 or PCIe 2.0 x8.

Obviously, the number of lanes on the card is a physical issue (i.e. how many wires it has). So presumably, if it is PCIe 3.0 x8 it only has 8 lines, so will run PCIe 2.0 x8 on my motherboard. Is that right?

If so, will it make any practical difference on performance?

Thanks.
March 5, 2014 9:18:04 AM

Yes will work fine in a v2x16 slot.

v3x8 has about near enough the same bandwidth as a v2x16, so shouldn't effect performance.
m
0
l
March 5, 2014 9:18:41 AM

In almost all cases, the PCIe x16 slot closest to your CPU is the x16 slot. If you put the video card into that slot, you'll have the bandwidth of 16 PCIe 2.0 lanes to work with.

From a bandwidth standpoint:
1xPCIe 3.0=2xPCIe 2.0
8xPCIe 3.0=16xPCIe 2.0
m
0
l
Related resources
March 5, 2014 9:27:26 AM

Sounds like your card will be running at 2.0 x8. The MB will set the PCIe slot to 2.0, your card can only access 8 lanes, this is will 1/2 the speed the card is capable of.
m
0
l
March 5, 2014 9:32:16 AM

Your card can run in both; PCIe 2.0 x16 and PCIe 2.0 x8.
Regarding performance, just to elaborate as example in pic:

I hope it answers all your questions. ;) 
m
0
l
March 5, 2014 9:53:58 AM

Thanks for all your answers. I think the jury's still out as some have said x8, some have said x16 and some have said it's capable of running in either! My gut reaction was the same as endeavour37a's.

Looking here, as between PCIe 2.0 x8 and PCIe 2.0 x16, it doesn't appear to make any difference anyway, even for cards which are very significantly faster than the one I've bought:

http://www.pugetsystems.com/labs/articles/Impact-of-PCI...

I've ordered it anyway now, so I'll see when I put it in the motherboard.

Thanks again.
m
0
l
March 5, 2014 9:59:55 AM

Andrew17857 said:
Thanks for all your answers. I think the jury's still out as some have said x8, some have said x16 and some have said it's capable of running in either! My gut reaction was the same as endeavour37a's.

Looking here, as between PCIe 2.0 x8 and PCIe 2.0 x16, it doesn't appear to make any difference anyway, even for cards which are very significantly faster than the one I've bought:

http://www.pugetsystems.com/labs/articles/Impact-of-PCI...

I've ordered it anyway now, so I'll see when I put it in the motherboard.

Thanks again.


enjoy for the best!!!
Post the results of cards as soon as you get it started. :D 
m
0
l
March 7, 2014 8:51:57 AM

I've received the card now, and confirm that it works in PCIe 2.0 x8 mode.

Also, if anyones interested I can also confirm that it works in CrossFire mode with my other card, an Asus R7240-2GD3-L, on my Dell Precision T5400 (Intel 5400 chipset on the motherboard).

Andrew

m
0
l
March 7, 2014 8:55:20 AM

Andrew17857 said:
I've received the card now, and confirm that it works in PCIe 2.0 x8 mode.

Also, if anyones interested I can also confirm that it works in CrossFire mode with my other card, an Asus R7240-2GD3-L, on my Dell Precision T5400 (Intel 5400 chipset on the motherboard).

Andrew



thanks for the update buddy. Enjoy!!!
m
0
l
!