Low hashrate when gpu is in primary pcie slot on main machine.

[waltsmith]

Hi guys,
Looking for a lil technical help.
Been mining scrypt based coins for a few months now and i've built a new computer with 2 280x's since my motherboard died in my old machine that had a 7950.
went ahead and got a new motherboard for the old machine so i could have 3 cards mining.
Here's my problem; On my old computer the 7950 got about 570 kh/s, bout 540k at an intensity that allowed the comp to be usable.
With the new MB and a reformat and fresh install of win7 and pretty much nothing but mining essential software that same card is now getting 620 k in my old rig.
In my new rig I have two identical 280x cards. in a non crossfired arrangement, the primary display gpu gets 550 k while the other gets 700 k.
Tried swapping the cards, same result!!
I'd say some setting in CCC or some other software/process is probabaly my problem but i have tried screwing with every setting i can think of and the primary GPU just runs slower.
Anyone else ever run into this, or any ideas?
Any help is much appreciated!!

Waltsmith

[torrance_btc]

OK.

Old machine had one GPU and pulled 570 khashes per second.

New machine has two GPU's, the primary gets the same 570 Kilohashes, but the secondary gets more (700)?

Am I reading that correctly?

I'd guess that what you're seeing is the overhead that windows is imposing. Your primary GPU runs your display, even if you're not doing anything with it, Windows is still probably reserving parts of the GPU for display effects, etc.

That's why the hard core miners run Linux without a GUI at all - that way every clock cycle of the GPU is devoted to mining insead of running a display that you're not looking at.

Or... maybe I misinterpreted, but I think that's what you described.

[waltsmith]

Sorry for the delay in replying i posted just before bedtime last night. lol
Yes, you got it correct windows or something is slowing down that primary, but thats just it.
It's not being slowed on the other rig with a fresh install of windows and not much else.
If its a software conflict(which im guessing it is) I thought maybe someone else had run into this problem of primary display gpu being throttled.

Machine being throttled software installed is:
Win 7 x64 sp1 current on updates including .net
catalyst 13.11
opencl app sdk 2.9
latest java
latest adobe flash player
Nero 10 suite
MS Office 2010 Home and Student
silverlight (for hulu and netflix)
vlc media player
as well as a host of other programs but none of which install any codecs or video editing capabilities as far as i know. 

waltsmtih

[pontiacg5]

You shouldn't loose that much hashrate, I have two 280x cards and GPU0 runs only 5-10mh/s slower in windows. Only doing something like opening firefox, thunderbird, corsair-link software, etc. slows GPU 0 down to ~630kh/s, GPU1 likes to bounce between 700-750kh/s when GPU0 is running firefox/cgminer both, else they both do 740-750kh/s.

I think you have a program stealing power, time to start closing processes till it picks up  

[waltsmith]

oh and i forgot to specify in my last post.
7950 that used to be my only card now gets about 625kh/s in the freshly installed machine.
Both cards currently in main rig are 280x.
I also use saphire trixx to overclock all the cards.
The 280x's are running at 1050 core 1500 mem stock voltage.
the 7950 is running at 1150 core 1500 mem.
Why no overhead on the secondary machine is what im wondering?

waltsmith

[pontiacg5]

You don't need trix to overclock these cards since you are not undervolting, I'd try using CGminer to clock the cards. It's also possible you are pushing them too hard, script is finesse not pure clock rate. It's entirely possible for 10Mhz of engine/mem speed to trash 750kh/s down to 600.

Then again, it's also possible you got a pair of cards that are totally different. No two 280x's work the same, for example I have two 280x cards that do 750kh/s on these settings...

--thread-concurrency 8192 --lookup-gap 2 --worksize 256 --gpu-engine 1080 --gpu powertune -20 -g 2 -I 13

But I have a set of 6 that use these settings for ~720kh/s. If I try the settings I just posted I get like 550kh/s. The cards in this machine have engine clocks between 1020 and 1050, no two are the same but they all average out to nearly 720kh/s at the right engine clock.



Keep fighting it, but you have to try new and different things and keep track of what you've done.

[waltsmith]

thx for the reply.
I'm actually using those same cgminer settings for both cards. I get 700ish with either card at those settings in the secondary pcie slot only tho.
that is, tc 8192 2 gpu threads i 13.
Have played with the overclock settings quite a bit. It just seems that its the most i can reasonably squeeze out of the cards. I've even considered that my problem might be a BIOS setting for that slot. Wouldn't know how to configure that tho. Pretty decent with BIOS settings but that one would be beyond me.
I've killed every process not necessary and did squeeze another 10-15k hash out of each card. Even the second one! lol But, still about 150k difference between the two.
Also, by using settings tc 20922 1 gpu thread and i 20 i can get about 650 when a card is on first slot, computer totally unusable tho.
However this higher setting results in a way lower hash in the second slot. like 550kh/s

Waltsmith

[pontiacg5]

It sounds like you managed to find two different cards, you might try running a higher thread concurrency (11200) and two threads on the first card, but leave the second card at 8192.

They both are exactly the same right? I have two different sapphire 280x's some have 2 8 pin power plugs, some have 1 6 pin and one 8 pin. The dual 8 pins likes a higher TC.

[waltsmith]

Again thx for helping, guess i'm not being clear tho.
Either card will get over 700kh/s...in the second pcie slot.
While either card get under 600 in the primary slot.
I've switched them out twice. Even the 7950 that i now have in the second rig gets only 500-525 when in that first slot.
just not willing to reformat tho. That puts my network down for a day or more getting everything back up just to TRY and get another 100kh/s.

waltsmith