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Anyone got any idea why the cards running on PCI 1x extenders run at half the clock speed  of my card on the 16x extender cable? Is it just coiincidence or is there some other setting I am likely to have wrong?

I cant work it out, they wont seem to ramp up to 925mhz when load comes on in either GUI minter or cgiminer

cgminer version 2.7.4 - Started: [2012-09-03 21:40:27]
-------------------------------------------------------------------------------
(5s):1259.6 (avg):1225.1 Mh/s | Q:19  A:46  R:0  HW:0  E:242%  U:16.9/m
TQ: 0  ST: 9  SS: 0  DW: 7  NB: 1  LW: 101  GF: 1  RF: 0  WU: 17.7
Connected to xxx with LP as xxx
Block: xxx...  Started: [21:40:27]
-------------------------------------------------------------------------------
[P]ool management [G]PU management {S}ettings [D]isplay options [Q]uit
GPU 0:  37.0C 4757RPM | 244.1/249.6Mh/s | A: 9 R:0 HW:0 U: 3.31/m I: 4
GPU 1:  37.0C 4888RPM | 249.8/248.6Mh/s | A: 9 R:0 HW:0 U: 3.31/m I: 4
GPU 2:  57.0C 5025RPM | 515.9/513.6Mh/s | A:14 R:0 HW:0 U: 5.15/m I: 5
GPU 3:  33.0C 4827RPM | 249.8/248.6Mh/s | A:16 R:0 HW:0 U: 5.89/m I: 4
-------------------------------------------------------------------------------


edit:

Just discovered in GPU Z that all the slow cards are set to run at 500mhz clock 150mhz memory for some completely unknown reason - any ideas as to why?

I get that if my card doesn't like it when AB sets the core clock using unofficial overclock = 2. I have to use AB to set my memory, and then use CGMiner to set my CPU

I've also thought about running them in that 500/150 low power mode. They get just a hair under 300MH/s, but use like 50-60W!

I assume AB = MSI Afterburner?

Changing the clock in AB and cgminer doesnt seem to affect anything other than the primary card for me, even though theyre "linked" :(

P.S. I am getting around 440w at the power point if I set everything low, so not sure its worth it except to save on noise and heat

What driver are you using?

12.4 catalysts

I am thinking they're stuck in low power mode for some reason and thus aren't following the clock that they're set to, but can't work out why.

Just a wild guess: try disabling ULPS.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E968-E325-11CE-BFC1-08002BE10318}

There are numbered keys in this registry location, perhaps more keys than you have GPUs. Some of them might be leftovers from earlier driver installs. You can check from device manager what the registry keys for your cards are. Just double click on the GPU, select details, and then view Driver key from the list. After you've found the right registry keys, change EnableULPS under them from 1 to 0. Then reboot.

Is your CPU usage pegged when CGMiner is running?  If so, this is why your cards aren't getting fully utilized.

Turn the intensity to 7 on each card (it looks like you're running on dynamic).

No CPU isnt maxed - it is running at about 15% with CG miner. Runs at about 2-5% with GUI miner at similar hash rate.

I tried turning the intensity to 9 and it still ran @ 500mhz clock

Lame.  So much for that idea...

The only other time I've seen this happen has been when the cards had a modified BIOS or when MSI Afterburner wasn't properly setting clocks.

No it's not a problem with the Intensity. Is there a reason you're using 12.4 for a driver instead of a newer one like 12.8?

This is the same with my experience. Can you reboot the computer and try running CGMiner without using AB?

Ahhh I was unaware of ULPS - that sounds like it will be the culprit - I will give that a try! Thanks!

I only tried AB after CGMiner was not producing results - i.e. the problem was there without AB installed. I think it will be ULPS. When I am back in front of the machine I will give that a go and report back.

P.s. no good reason for 12.4 vs 12.8. Is there a noticeable improvement in any regard?

Actually there is a bug present in 12.4 which causes exactly what you're experiencing.  In order to fix it you need dummy plugs.  With 12.8, you don't need them.

Updating to 12.8 fixed the speed problem, thanks!