Question.. on two 6950 cards, two different hash rates

[6950miner]

I setup a box with two identical 6950 xfx cards.  Configured GUIMiner for pooling no problem.. however one 6950 card runs at 306 mhash, the other only 85 to 95 mhash.  Cards are setup with crossfire cable installed and configured as such.  Reasons why the 2nd card won't run at speed?

[1715110944]

1715110944

[1715110944]

1715110944

[Radeon]

do you have two "tabs" (workers) set up in guiminer? with the pull down menu select 1 card, the other tab select the other card?

[Seuros]

remove crossfire!

[zerokwel]

remove crossfire!

I second that.

[Einewton]

remove crossfire!

I second that.

I third that... I have 5 of thoes cards and I get ~218 Mh/s per card... I don't overclock because cooling isn't so good, and I run them around 75C 100% of the time, and if I OC it, i'm afraild it'll fry.

[smokie128]

I don't know how much PCIe bandwith a miner takes up, but i guess the reason could be in the different PCIe data rates the mobo supports.

e.g. my board has one PCIe slot with the full x16 bandwith and an additional one limited to x4.
It could also be the crossfire thing, as the first card has too many mining operations running to properly support the second card with enough data.
Just a guess because i don't know what interface the second card uses to get it's data from...

[gopher]

remove crossfire!

I second that.

I third that... I have 5 of thoes cards and I get ~218 Mh/s per card... I don't overclock because cooling isn't so good, and I run them around 75C 100% of the time, and if I OC it, i'm afraild it'll fry.

I fifth that.

Crossfire really adds no value to the bitcoin mining

[pbj sammich]

I don't know how much PCIe bandwith a miner takes up

the slot doesn't make any difference, you'll get the same hash rate on an x1 slot so its not that

I agree you should remove the crossfire cable (you'll need a dummy plug though) ... but even with it on those speeds are off - you should be ~350+ with that card pretty easily

You sure the first miner is set to [0-0] Cayman and the second is [0-1] Cayman in the drop-down?

What power supply do you have?

[6950miner]

Well.. after little more fiddling I thought I had it whipped.. alas.. no.  Removed crossfire cable.  Noticed that GuiMiner recognized one card as Caymen [0-0], but Caymen [0-1] was gone.. but new option [1-1] Cormorant appeared.  Same deal though, they were just accessing the same GPU.  Next I moved the DVI cable to the second GPU (hoping to get the OS to see the card had a monitor attached and get that card running), monitor did respond and the second GPU came online and started mining at full speed (mining 305 Mhash (just stock 840 MHz, not OC'd).   After a few hours had to reboot (accidentally clicked on a video when web browsing which of course instantly locks the PC).  I could not replicate what I did earlier and get the same result.  Weird thing is now if I disconnect the DVI cable CPU hard locks instantly so I can't even try moving the cable from one DVI out to the other card.   Has anybody successfully just switched monitor cables around so you didn't have to make dummy DVI plugs?  I've read through a bunch of post here but haven't seen anybody really have that much trouble getting two cards to mine before.. I guess everybody is using UNIX.

Power supply is OCZ 1000 watts, ASrock Extreme 4 MB, cards are XFX 6950's 2gb..  win 7 64

[6950miner]

All is well now.. definitely had to have a 2nd monitor attached.. stopped by 'Worst Buy' and picked up a DVI-VGA adapter, dug up an old dell 17" fp.  Soon as I hooked that up all was well..  Both cards show up in GUIMiner, and both 6950's mine 330 Mhash plus with little overclock.. (additional shaders not unlocked).  Crossfire cable is installed and cross fire is running so it seems that crossfire doesn't make any difference whether it's turned on or not in my case.  Btw.. Radio Shack didn't have any electronic components...  I've always wondered how that place stays in business with that business model.. everything they have there is crap (always has been).. and even if I did want to build my own Ham radio from scratch they don't have any electronic components anyway, LOL.  Also I've noticed that even 'Worst Buy' seems to carry less and less computer supplies.  Really wish Fry's would come to the East Coast.. that place is heaven if you like shopping for computer stuff in person or just need to get something right away.

[makiet]

remove crossfire and use dummy plug on the 2nd card

[lowlevel]

I bought 3 sapphire Radeon HD 8530's.... one open box, two new.
The open box one got about 272 out of the box, while the other two did 265.

I'm guessing someone messed with the open one... but no idea.

-lowlevel

[Trini8ed]

Do this method i used for my cards remove crossfire bridge and make a vga dummy plug

http://www.overclock.net/folding-home-guides-tutorials/384733-30-second-dummy-plug.html

[6950miner]

Seems to be working fine with 2nd monitor attached.. so I don't need the dummy card... next issue been getting recently
only one card at a time connecting to the pool...

error messages from console....

No more backup pools left. Using primary and starting over
2011-07-08 02:06:40: Listener for "xxxxxx": 08/07/2011 02:06:40, Problems communicating with bitcoin RPC 0 2
2011-07-08 02:06:46: Listener for "xxxxxx": 08/07/2011 02:06:46, Problems communicating with bitcoin RPC 1 2
2011-07-08 02:06:52: Listener for "xxxxxx": 08/07/2011 02:06:52, Problems communicating with bitcoin RPC 2 2
2011-07-08 02:06:58: Listener for "xxxxxx": 08/07/2011 02:06:58, Problems communicating with bitcoin RPC 3 2

connecting to slush pool.. not sure what the scoop here is.. not sure if something on the pool side or not.

After watching it more they both seems to be dropping in and out at times.. I'm guessing this is on the server side and why people have accounts at
multiple pools so when one 'dies' it will roll over and start mining at another pool that it can connect to.