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Author Topic: 6990 Hash rate drops significantly when using both GPUs  (Read 3417 times)
mjhorn
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May 29, 2011, 06:43:36 AM
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So I finally got my 6990 setup running correctly under Ubuntu 11.04. Been doing some testing with the various settings, and so far with a single core running I'm able to hit just over 400MH/s. However, as soon as I enable the second core, both drop to more in the 340MH/s range. Is this to be expected with a dual GPU card like this? Are there any settings you'd suggest modifying to see if it makes a difference?
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Maxxx
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May 29, 2011, 07:25:39 AM
 #2

So I finally got my 6990 setup running correctly under Ubuntu 11.04. Been doing some testing with the various settings, and so far with a single core running I'm able to hit just over 400MH/s. However, as soon as I enable the second core, both drop to more in the 340MH/s range. Is this to be expected with a dual GPU card like this? Are there any settings you'd suggest modifying to see if it makes a difference?


This does not happen under Windows 7. On all of my 6990's, all single GPUs are running at 405Mhash/s max. How is CPU usage/aggression level?

Also, you probably know but be sure to monitor GPU temps as they could be throttling.

Code:
aticonfig --odgt --adapter=all

I believe.

Time is money. This means that if you have spare time, you can use it to make money.

Modular, open, and stack-able miner case.
mjhorn
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May 29, 2011, 08:17:08 AM
 #3

I can keep the aggression high since its a server that I don't need a responsive desktop on. Also, temps under load stay in the upper 70s to low 80s range, regardless of one or both cores going.

The one thing I did notice however, is that when I'm only mining with one core, GPU usage as displayed by aticonfig --odgc is a constant 99. However, mining on both cores results in usage on both to alternate between 100% and 0%.
lastobelus
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May 29, 2011, 10:51:03 AM
 #4

Check your cpu usage. Is it pegged? Also, does the primary display run by itself get a steady hash rate as high as the secondary card run by itself?

There is some kind of issue with the ubuntu gui that causes cpu to max out when mining on the primary display, slowing down ALL gpus.

If you switch to headless it will go away.

Cpu usage should be < 10% if things are working properly.
mjhorn
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May 29, 2011, 01:31:41 PM
 #5

CPU generally never jumps over a few percent. Either card, when run on it's own, is able to hit 400MH/s. Also, the setup is already headless.
clonedone
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May 29, 2011, 02:48:34 PM
 #6

So I finally got my 6990 setup running correctly under Ubuntu 11.04. Been doing some testing with the various settings, and so far with a single core running I'm able to hit just over 400MH/s. However, as soon as I enable the second core, both drop to more in the 340MH/s range. Is this to be expected with a dual GPU card like this? Are there any settings you'd suggest modifying to see if it makes a difference?


This does not happen under Windows 7. On all of my 6990's, all single GPUs are running at 405Mhash/s max. How is CPU usage/aggression level?

Also, you probably know but be sure to monitor GPU temps as they could be throttling.

Code:
aticonfig --odgt --adapter=all

I believe.

what miner do you use and what flags do you use?
can you please paste the code?

Maxxx
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May 29, 2011, 03:58:58 PM
 #7

So I finally got my 6990 setup running correctly under Ubuntu 11.04. Been doing some testing with the various settings, and so far with a single core running I'm able to hit just over 400MH/s. However, as soon as I enable the second core, both drop to more in the 340MH/s range. Is this to be expected with a dual GPU card like this? Are there any settings you'd suggest modifying to see if it makes a difference?


This does not happen under Windows 7. On all of my 6990's, all single GPUs are running at 405Mhash/s max. How is CPU usage/aggression level?

Also, you probably know but be sure to monitor GPU temps as they could be throttling.

Code:
aticonfig --odgt --adapter=all

I believe.

what miner do you use and what flags do you use?
can you please paste the code?

Replied to your PM but will list summary here too.

The most important factor is bumping core clock up (mine is at 940) and using the switch on the top of the 6990's to use the unlock/super/kill the polar bears mode. Then phoenix with poclbm. The rest of the options just tweak to maximum performance.

Time is money. This means that if you have spare time, you can use it to make money.

Modular, open, and stack-able miner case.
Saturn7
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May 29, 2011, 04:12:12 PM
 #8

Have you disabled Cross Fire?
When crossfire is enabled commands are sent to the 2nd GPU through the 1st GPU creating a bottleneck.

First there was Fire, then Electricity, and now Bitcoins Wink
mjhorn
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May 29, 2011, 05:09:33 PM
 #9

Currently mining using the following:

 ./poclbm.py  -d0 -w 128 -r 5 -f 0 -v
 ./poclbm.py  -d1 -w 128 -r 5 -f 0 -v

When the first one is launched it runs at 400MH/s until the second is launched at which device 0 levels off around 350 and d1 around 325. Crossfire is disabled. I've also tried an equivalent setup with phoenix using both the poclbm and phatk kernels. This one edges them out just slightly for my setup.
IlbiStarz
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May 29, 2011, 05:46:35 PM
 #10

Well I'm pretty sure that's normal...mine does the same thing. Together it does 700mh/s so that is near the mining hardware comparison charts.

It's better to be pissed off, than to be pissed on.
BTC : 1UgM1rqL9mFtH4PHF8TgvAaceymaKmhmP         LTC : LgCGw2WrRphr94RYS1qXHj2PUuYrTap4vk
FC : 6jc9PEmqxpMSxydfepHtshE4f2jMom1dAJ
Saturn7
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May 30, 2011, 11:46:11 AM
 #11

Have you increased the stock voltage?
The 6000 Series dynamically underclocks if there is a lack of power to prevent a crash.
In windows the catalyst control centre lets you up the voltage by 20%.

First there was Fire, then Electricity, and now Bitcoins Wink
mjhorn
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May 31, 2011, 01:17:51 PM
 #12

I haven't increased the voltage beyond the onboard switch being set to position 1. After some more experimentation thought, it seems to be heat related. When both are initially started, I can usually get a minute or so where they are running at ~400MH/s each. Then as the temp climbs and levels out in the low 80s, the hash rate drops a bit and settles. When I opened the case and got some additional fans going, if I can keep the temps in the mid to upper 70s under load, both cores are able to stick near 400MH/s. So with that in mind, any ideas for the most efficient way to improve cooling with this card? The case is a big with lots of room, and all cabling is routed on the back side of the motherboard. Currently has 3x200mm fans and a 140mm as well, so I think airflow inside the case is going to be to tough to improve. I suppose water cooling might be an option? I don't have a ton of experience water cooling, but I assume there are blocks available for the 6990 by now?
njloof
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May 31, 2011, 02:20:59 PM
 #13

I suppose water cooling might be an option? I don't have a ton of experience water cooling, but I assume there are blocks available for the 6990 by now?
http://www.koolance.com/water-cooling/product_info.php?product_id=1117
nathanrees19
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May 31, 2011, 02:29:11 PM
 #14

Then as the temp climbs and levels out in the low 80s, the hash rate drops a bit and settles. When I opened the case and got some additional fans going, if I can keep the temps in the mid to upper 70s under load, both cores are able to stick near 400MH/s.

Does the GPU fan (or fans) run at full speed? I found that (in Windows) my 6950 would happily go past 90C and the drivers wouldn't bother increasing the fan past 38%. Manually putting it up to 45% brought it down to 80C.
mjhorn
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May 31, 2011, 07:11:03 PM
 #15

I did notice that leaving the fans on auto they typically never spun up past about 40%. I've gone to manually setting the speeds on them for the moment. I can keep the temps in the low 80s at 50-60% fan speed, and currently at 100% is where the temp is maxing out just about 80, but I'm getting somewhat better performance from the card as well. Currently I'm running in the 700-725MH/s range up from more like 650-675.
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