PCIe 16x (x4 mode)

[azrul]

Hi,

PCIe 16x (x4 mode)

What is the (x4) stands for? I would like to crossfire 2 HD6790 on an Asus p8z68 v-lx mobo, it got 2 16x PCIe lanes, but one of them got the 'x4' which I'm not sure of. Any advice?

I also saw a note that that lane was sharing bandwidth with two other x2 lanes. So if I don't use the 2 x2 PCIe lanes. Does it mean that the x16 lane still consider as it is?

Thanks

 

[addzy94]

All i know is if it is higher number(x) it is better.

I also found this page.

http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/25.html

 

[azrul]

All i know is if it is higher number(x) it is better.

I also found this page.

http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/25.html

Hi addzy94,

Many2 thanks for that. So it means that even if its running on x4, its only 5% degrade on the performance. So i guess, i would not effect much though.

 

[GozerHozer]

For Crossfire or SLi, have a good PSU.
The Asus MB you listed only has AMD/ATI Crossfire support, so you an only us an AMD/ATI video card in crossfire.

I had 2 ATI 4870 x2 (4x crossfire) in my last rig and had a 1200w PSU.
New Rig has a EVGA GeForce GTX 590 Classified Hydro Copper-H2O cooled

Nvidia has less Micro-studder than ATI in Crossfire/SLI.

If you only have 1 PCI-E 16X slot, I would not use 2 in Crossfire.
Get a Dual core Video card, its a bit slower than 2 in crossfire, but not by much.

 

[azrul]

For Crossfire or SLi, have a good PSU.
The Asus MB you listed only has AMD/ATI Crossfire support, so you an only us an AMD/ATI video card in crossfire.

I had 2 ATI 4870 x2 (4x crossfire) in my last rig and had a 1200w PSU.
New Rig has a EVGA GeForce GTX 590 Classified Hydro Copper-H2O cooled

Nvidia has less Micro-studder than ATI in Crossfire/SLI.

If you only have 1 PCI-E 16X slot, I would not use 2 in Crossfire.
Get a Dual core Video card, its a bit slower than 2 in crossfire, but not by much.

I see, many thanks for the reply. I'm in Malaysia actually, so the price for a dual core card is really a pain here. lol. But nvm, I'm still thinking of doing crossfire just for interest sake. If something not going well, I can still just sell the card and get a new one 5 MONTHS LATER. lol..

Btw, I have a 600Watt psu at the moment, shouldn't be a problem right? And the board do have 2 PCI-E 16x slot but one of them is noted with a '4x mode' which I'm not really sure of what it means.

Anyone got any idea what is that "4x mode" means? Plsssss..

 

[Guest]

And the board do have 2 PCI-E 16x slot but one of them is noted with a '4x mode' which I'm not really sure of what it means.

Anyone got any idea what is that "4x mode" means? Plsssss..

it means that even though it is a x16 slot it will run at x4 speed.
"An example is a ×8 slot that actually only runs at ×1. These slots allow any ×1, ×2, ×4 or ×8 card, though only running at ×1 speed. "
http://en.wikipedia.org/wiki/PCI_Express

in other words, it will run a x1, x2 and x4 at default speeds but x8 and x16 at x4 speeds.

 

[azrul]

it means that even though it is a x16 slot it will run at x4 speed.
"An example is a ×8 slot that actually only runs at ×1. These slots allow any ×1, ×2, ×4 or ×8 card, though only running at ×1 speed. "
http://en.wikipedia.org/wiki/PCI_Express

in other words, it will run a x1, x2 and x4 at default speeds but x8 and x16 at x4 speeds.

Thank looniam you for that . It's clear now. Btw, based from addzy94 comments above, though it's running on x4 speeds, the degrade will only be around 5% (test was running on 5870). So hopefully it wouldn't noticed much. hm.. I'm gonna need to get a new mobo i guess.

 

[Guest]

Thank looniam you for that . It's clear now. Btw, based from addzy94 comments above, though it's running on x4 speeds, the degrade will only be around 5% (test was running on 5870). So hopefully it wouldn't noticed much. hm.. I'm gonna need to get a new mobo i guess.

is that p8z68 v-lx a gen 3 board?

if so then according to this:
http://event.asus.com/2011/mb/PCIe3_Ready/

it will be pci 3.0 ready and support ivy bridge. what that means is with pci 3.0 it will double the bandwidth of the lanes and *theoretically* turn that x4 mode into x8 mode with an ivy bridge cpu. and a pci-e 2.0 card won't saturate a x8 slot.

so maybe wait until IB and see if it happens before making a purchase.

 

[azrul]

is that p8z68 v-lx a gen 3 board?

if so then according to this:
http://event.asus.com/2011/mb/PCIe3_Ready/

it will be pci 3.0 ready and support ivy bridge. what that means is with pci 3.0 it will double the bandwidth of the lanes and *theoretically* turn that x4 mode into x8 mode with an ivy bridge cpu. and a pci-e 2.0 card won't saturate a x8 slot.

so maybe wait until IB and see if it happens before making a purchase.

Here's the official reference link :-

http://www.asus.com/Motherboards/Intel_Socket_1155/P8Z68V_LX/#specifications

Seems like it is a PCI-E 2.0. Btw, I remember when I was Goggling around earlier and found an article that discuss this issue as well. Somebody mentioned that it would not really effect much weather it is a x4, x8 or x16 on pcie2.0 as the bandwidth used when processing on a GPU card mostly runs around inside the GPU card and out to the video output. It's logic though, but in CFX terms, it might be a different scenario as it is scaling with each other.