Riser cable problems

[pontiacg5]

Hey everyone!

I'm having a problem with 4 8x to 16x riser cables I ordered online. I can't get them to work, half the time windows refuses to boot and the other times it causes artifacts and device manager codes (not enough resources to start?) If I run all 4 on risers I can detect and use the first one, but it's crazy unstable. Usually loops, always restarting around the time PCH DXE Initiation started which is odd because I've disabled mostly everything I don't need in bios.

My motherboard is made to run cards like this, has 4 x16 slots that all work at 8x with my ivy processor. It has a built in sata plug that is described as for adding power to the pcie rails with three or more cards. All 4 work pretty well directly in the board at 8x speed, they just get hot! 1300W Rosewill powering it all.

I've read about changing pcie latency in the bios, but my board doesn't seem to have an option for that. My risers are unshielded and unpowered, should I try to add power/shield to them even though I know the motherboard has more than enough power?

Or did I just get a crappy batch? I've seen pics of guys running these cards unmodified, so wtf!?

This is 4 7970 Ghz, gigabyte g1.sniper 3, i3 3220. OC to 1150 gets a steady 2800MH/s, but temps are low 90s open bench with a very high velocity external fan.

Thanks for looking!

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[pontiacg5]

Cables wrapped in aluminum don't seem to do much better...

Any suggestions? Did I just get 4 bad cables?

[Malawi]

I assume that those are not powered risers.

If so the cards don't get enough power, and you risk frying your MB.
3 of them will prob work, but then there is also the risk of destroying the MB, but it will take slightly longer.

[pontiacg5]

Yes, typically I'd assume that would be the case. However this is a motherboard specifically designed to run quad SLI/Quad crossfire (4 16x slots, spaced evenly.) It has an auxiliary input to add extra power to the PCIe slots. Assuming the risers don't add any load there should be no reason that powered risers are necessary as they are already powered by the motherboard. These cards run fine directly on the board...

Besides, I can't get it to work with three cards anyway. Can't even get two, I've never seen so many artifacts before in my life...

WTF am I doing wrong?



 

[Malawi]

Yes, typically I'd assume that would be the case. However this is a motherboard specifically designed to run quad SLI/Quad crossfire (4 16x slots, spaced evenly.) It has an auxiliary input to add extra power to the PCIe slots. Assuming the risers don't add any load there should be no reason that powered risers are necessary as they are already powered by the motherboard. These cards run fine directly on the board...

Besides, I can't get it to work with three cards anyway. Can't even get two, I've never seen so many artifacts before in my life...

WTF am I doing wrong?

Sounds weird. Have you got a Catalyst center that is above v 13.1?

I just got two 7950's for gaming/mining. Installed from the CD that came with the cards and expected to get the latest version. But alas it was 12.something. I had artifacts around the borders of my windows while mining. After upgrading to Catalyst Center 13.5 the artifacts dissapeared and my LTC hashrate went up (Or maybee I just had gotten better settings, not sure about that either.  )

[pontiacg5]

I'm running 13.4 right now, I don't have artifact problems till I try running on risers.

This is a PITA, I tried everything but powered risers last night and still never got it to work reliably. Maybe I should have just went with 1x cables?

[Malawi]

I'm running 13.4 right now, I don't have artifact problems till I try running on risers.

This is a PITA, I tried everything but powered risers last night and still never got it to work reliably. Maybe I should have just went with 1x cables?

I'm still in the research phase for building my first rig, and have no real-life exp.
Seems like you have been trough most of the stuff i would consider except the powered risers.
Guess you might wanna try moving the cards/risers around a bit, but pretty unsure if that will do any difference.

Let's hope someone with a bit of experience in rig-building sees this thread and chimes in.

[prophetx]

I have the same issue with standard size pcie riser cables.  It sucks bc I cannot fit the 3rd card without them...  even when I have 2 cards and put the secondary card on a riser everything boots up, and as soon as cgminer starts I get BSOD.

my next step is to get a riser with a molex cable

[hashrateproducts]

I have the same issue with standard size pcie riser cables.  It sucks bc I cannot fit the 3rd card without them...  even when I have 2 cards and put the secondary card on a riser everything boots up, and as soon as cgminer starts I get BSOD.

my next step is to get a riser with a molex cable

Hi Prophetx,

Have you tried running a couple cards at a time without any risers to confirm that the issue is caused the cables?

I recommend molex cables for any configuration with 4 or more GPUs to minimize the risk of frying the motherboard unless it specifically states it supports 4 way crossfire.

[prophetx]

I have the same issue with standard size pcie riser cables.  It sucks bc I cannot fit the 3rd card without them...  even when I have 2 cards and put the secondary card on a riser everything boots up, and as soon as cgminer starts I get BSOD.

my next step is to get a riser with a molex cable

I figured out why it was not working.  the 3 large pcie slots are 16x, 8x and 4x.  i was using 16x cables and also one of the cables may be faulty as well.

So I took 1 16x cable and cut the cable down to a 4x and now i have 3 cards.  2 in slots and one on a riser cable (I seem to have lost my 3rd cable with all the junk i threw out last week).  I tried to use the 2nd cable I had and cut it into an 8x but the system was not even seeing my card in the 2nd slot so I'm pretty sure that cable is dead.

Anyway I will buy a few more cables and see if I can get the other 2 cards to work on risers b/c card one has no room for air circulation.  Apparently on this mobo the pcie 16x slot gets down graded to a 8x when there is a card in the 8x, but it does have 3 1x pcie so perhaps I will get those instead.  

For 1x risers do those require a molex cable? I think I have only one power power outlet left on my psu

[pontiacg5]

I have the same issue with standard size pcie riser cables.  It sucks bc I cannot fit the 3rd card without them...  even when I have 2 cards and put the secondary card on a riser everything boots up, and as soon as cgminer starts I get BSOD.

my next step is to get a riser with a molex cable

I figured out why it was not working.  the 3 large pcie slots are 16x, 8x and 4x.  i was using 16x cables and also one of the cables may be faulty as well.

So I took 1 16x cable and cut the cable down to a 4x and now i have 3 cards.  2 in slots and one on a riser cable (I seem to have lost my 3rd cable with all the junk i threw out last week).  I tried to use the 2nd cable I had and cut it into an 8x but the system was not even seeing my card in the 2nd slot so I'm pretty sure that cable is dead.

Anyway I will buy a few more cables and see if I can get the other 2 cards to work on risers b/c card one has no room for air circulation.  Apparently on this mobo the pcie 16x slot gets down graded to a 8x when there is a card in the 8x, but it does have 3 1x pcie so perhaps I will get those instead.  

For 1x risers do those require a molex cable? I think I have only one power power outlet left on my psu

16x cables should work even if the lane speed is only 8x or 4x. The card is always 16x, but sometimes it just doesn't work at full speed, or bandwidth I guess I should say. It shouldn't be necessary to cut them down, in other words.

Buying 16x cables when you know it only works at 1x/4x/8x speed is kind of a waste though. That's why I bought 4 8x cables because all 4 of my cards run at 8x.

1x risers don't require a molex cable any more than a 16x cable would. The first "tooth" of the card slot is for power, everything else is just data. If you run more than 4 cards I'd add a powered riser for every card more than three, unless your mobo has a sata power plug specifically for powering the pci-e bus.

I have a feeling you are in the same boat as I, specifically the cables work but they add too much latency or something. I can tell that Windows is trying to load the cards that never show in device manager, probably hitting some sort of timeout while booting or something. I'd occasionally be able to detect one or two cards on risers, but they still weren't operating properly judging by scrolling in Firefox and other simple windows tasks.

If you haven't already tried, wrap your cables in some aluminum tape to try and shield them from electrical interference. Be careful though, the stuff is conductive. It didn't work for me, so good luck either way!

[ewitte]

Not sure about that 16X is designed for 75W supposedly a lot of times 1,4,8 is only rated for 25W.

[pontiacg5]

The way I understand it is that all pci-e slots share the same current supply. Drawing too much from the pci-e current capacity will eventually cause something to fail, generally the ATX 24 pin power connector.

So, removing the potentially larger current draw of one card should be enough. You do that by using powered risers. 

I completely believe that a 1, 4 or 8x slot might not be rated for as high a current as a 16x slot, but for this application it doesn't matter.

[ssateneth]

Never used powered risers on anything, only standard 1x > 1x risers. I have 53 gpu cores across 7 rigs, been mining since july 2011.

[prophetx]

hmm ok thanks!

well i'm going to order some 1x risers and see how that turns out

right now i have all 3 cards working and the only issue is that the heat on the first card is a bit high but i was about to lower it by 10 to 70 by putting the fan from the PSU in a position where it blows between the 1st and 2nd card

i have not built a rack for this yet, but i would like to see if i can squeeze in a 4th 6950, though i would need to upgrade the 850w psu

[cdog]

Ive never gotten risers to work properly...

[gbx]

Cables wrapped in aluminum don't seem to do much better...

Any suggestions? Did I just get 4 bad cables?

Did you ground the shield?  If not you might amplify the issue (create an antenna).