Need help troubleshooting addition of third 7970

[Big Daddy]

Hi All,

I've been running the following rig for a month with no issues:

Mobo:Gigabyte GA-990FXA-UD5 R
CPU: AMD 4-Core FX-4100 3.6G 8M R
RAM: 4GB (can't remember which, cheap sticks)
HDD: 60gb Corsair Force 3 SSD
OS: Xubuntu
GPU:  (2x) Gigabyte GV-R7970C-3GB HD7970 R
PSU:  Corsair HX1050
Miner: cgminer

Mining LTC I am seeing a consistent 715kh/s per card, so all has been good.

I have also been running a third Gigabyte GV-R7970C-3GB HD7970 R on a separate box as I could not run all three without serious heat issues on the first, I as seeing 715kh/s as well on this card.

I finally picked up a 16x riser and last night I built a frame to hold the card up, and support my ghetto fabulous cooling system...WalMart box fan :-)

I have it running (about 24hrs now) and the riser seams to be working without heat issues of its own but I have not been able to drive the hash rate past the low 500's per card.

So my question is, is the lower hash due to a power issue, is the 1050 just not enough?  Is it a config issue?  Or is it something else I am missing completely?

Any and all help will be most appreciated 

[gbx]

Maybe a slight voltage drop due to the increased distance?  Can you up the voltage to the cards a bit to compensate?

[BlazinBeaches]

Have you tried reapplying your overclock profile settings?  I'm not sure what you are using but I notice with Afterburner I need to reapply my profile from time to time, some kind of bug.  Luckily I'm moving the rig to linux soon and will just use all cgminer commands.

There should be no speed loss.  I use 1x risers on 6 cards and have full speed.  Even when the risers were previously unpowered the speed was near full.  I noticed I did gain a very slight speed boost by turning them into powered cables.

Are they all 16x risers?  I'm not sure if that would cause an issue or not by using more bandwidth than the mobo can supply

[Big Daddy]

All three cards have dropped, not just the one on the riser.

[Big Daddy]

Good to know about the 1x, been thinking of picking up some.

[Big Daddy]

Have you tried reapplying your overclock profile settings?  I'm not sure what you are using but I notice with Afterburner I need to reapply my profile from time to time, some kind of bug.  Luckily I'm moving the rig to linux soon and will just use all cgminer commands.

There should be no speed loss.  I use 1x risers on 6 cards and have full speed.  Even when the risers were previously unpowered the speed was near full.  I noticed I did gain a very slight speed boost by turning them into powered cables.

Are they all 16x risers?  I'm not sure if that would cause an issue or not by using more bandwidth than the mobo can supply

I am running cgminer in Linux, I've replaced my config file a few times.   I am running two cards on the MOBO, and one card up on a 16x riser.

[BlazinBeaches]

My guess is the mobo can't supply the bandwidth.  But using 1x risers on all cards including the current two on the mobo, should alleviate all the tension and bring speeds back to normal.

[Big Daddy]

If I wasn't clear before, the riser I am using is unpowered, could this be part of the issue?

Going to splice in a molex tonight and will report back.

[BlazinBeaches]

Non-powered riser is not the issue.

[Big Daddy]

Non-powered riser is not the issue.

DRAT

[Big Daddy]

I use 1x risers on 6 cards and have full speed.

BB, what MOBO are you running?  I'm still learning...obiously  ... does running six 1x risers mean you can run a 1x riser in a 4,8 or 16x slot on the MOBO?

[Big Daddy]

so I experimented a bit tonight to no great avail...BlazinBeaches your MOBO bandwidth thought is looking more and more the culprit unless it is a script issue.

I jumped the ATX on a spare 600w PSU I have and connected it to the card I have up on the riser.  To refresh, two cards on the MOBO, one up on the riser.  My hash didn't budge a bit, hung tight at 500kh/s give or take.

I know you said the power riser was not the trick but I had to try  , did a bit of homebrew and powered up the unpowered riser I had been using...but again, no difference.

http://www.stinkinhippie.com/images/photo.JPG

So I will continue to mess with the config file and will order three 1x powered risers to see if that does the trick.

Anyone else have any ideas?