PCI risers and Crossfire?

[GiraffePencils]

Hey all,

I was wondering if it would be possible to have 2 GPUs in crossfire, and both on PCI riser cards?

I was thinking if they're both the same length as it's a serial bus it would be fine, just wanted to check to see if anyone had done it before so I could either go ahead or save myself the headache

Thanks

 

[GiraffePencils]

No one ?

 

[snips86x]

Why would you want to use risers? What's the motherboard & case you have?

 

[GiraffePencils]

It's for a PC Desk build, To keep the whole setup flatter I was exploring the possibility of having them on risers so they can be laid down

 

[Orangey]

IIRC there might be a problem having the primary card on a riser. Some quick googling throws up this which might help:

https://litecointalk.org/index.php?topic=8745.0

Also you want powered risers, although maybe if the mobo has molex plugs onboard near the PCI-E slots you could skimp out.

 

[GiraffePencils]

Hmm that's talk of mining rigs,
This would be for gaming, and in crossfire.
Might need more googling

 

[Orangey]

It's still relevant, but if you don't want help OK.

 

[GiraffePencils]

sorry, I didn't mean it to come across as dismissive.
I read the article, it just didn't cover the subject of crossfire/SLI, more troubleshooting the connection with risers, which will no doubt come in handy.

The more googling was a comment that I would need to google, not criticizing you for googling for me.

I'm sorry If there was a misunderstanding

 

[snips86x]

Have a look through the projects section of the forum. A few members have done desk and scratch builds using risers. Could always see if they had any issues, but not sure if crossfire has been done yet!

 

[ubersonic]

I read the article, it just didn't cover the subject of crossfire/SLI, more troubleshooting the connection with risers, which will no doubt come in handy.

It doesn't need to cover Xfire/SLI as risers are irrelevant to them (it's not like one card will get the data first if its on a shorter riser or anything) the only thing you need to do is make sure you have adequate power to the cards.

 

[GiraffePencils]

risers are irrelevant to them

Well this is is kind of what I'm looking to hear, but can't find any evidence to support this.
As the signals would take longer (this difference may be negligible, but that's why I'm asking) than in a non-riser situation I was wondering if this would cause a problem or would the PC be able to handle it.

 

[ubersonic]

Electricity travels at lightspeed IIRC, it's not going to make a difference, plus the fact that the PCI-E slots are all different distances from the CPU socket in the first place shows they don't need to be the same length. Any issue you could encounter would be due to the riser cable quality or power, both of which should not happen with quality powered risers (but sadly the is now a global surplus of cheap and nasty ones around due to the recent mining boom and bust).

 

[GiraffePencils]

Electricity travels at lightspeed IIRC, it's not going to make a difference, plus the fact that the PCI-E slots are all different distances from the CPU socket in the first place shows they don't need to be the same length. Any issue you could encounter would be due to the riser cable quality or power, both of which should not happen with quality powered risers (but sadly the is now a global surplus of cheap and nasty ones around due to the recent mining boom and bust).

Well, I'm really not trying to argue, just asking if anyone knew someone who has done it or KNOWS it would work.

While the PCI slots are different distances, they might be the same track length away, At my work a lot of components need to have the same track lengths while being different distances, as the timing is important, I wasn't sure if the new length to the GPU's would be withing the crossfire tolerance.

I understand the power implications, and yes the price and availability of decent Risers is quite irritating these days.

 

[BloodyL]

Not true Uber, the PCI-E sockets may be different distances from the CPU however that will have been taken into account by adding more distance in the PCB tracks for the closer sockets than the distant ones, thus allowing all sockets to receive data at the same time.
That's why you'd find the old PCB surface layer tracks that snaked all over the board from one pin to the next when they are right next to each other.