Quote from: hsk81 on May 01, 2013, 02:23:09 AM

Hi everybody,

I'm relatively new to mining and have the following setup:

Graphic cards: 2x ASUS HD7950 DirectCU II TOP GDDR5 3GB 384Bit AMD Radeon DX11.1;
MB: ASUS M5A99FX PRO R2.0 AMD 990FX/SB950 DDR3 2133MHZ(O.C.);
CPU: AMD FX X4 4100 SOKET AM3+ 3.6GHZ 12MB CACHE 32NM;
RAM: CORSAIR 8GB VENGEANCE DDR3 1600MHZ CL10 (single module);
PSU: GX 80PLUS 750W (bronze, 85% efficiency);

I don't use any risers; if a test each device separately I get a performace of about 580kH/s @ 1.090V (did not tweak extremely long, might get higher numbers); this is fine. But when I try both cards together then one of then cards voltage drops to 0.800V with corresponding engine clock down to 300Mhz; the other cards is fine but my overall performance is lower than 580kH/s.

I tried increasing the SB (Southbridge) voltage in the BIOS but that did not help at. Tried to combine a Sapphire 7950 with an Asus 7950 and got the same problem: One of the cards has systematically significant lower voltage (and therefore lower engine clock). I'm quite stuck .. I suspect the motherboard, but I feel with all its tweakable parameters a litte overwhelmed .. Sad

My dear,

first of all you should get easily 570khash on each maybe 600 with 72C temp (room temp25C) with stable condition =>1 week
1st- get nice cheap professional PSU like delta series for IBM serveres - you can get them under 20 bucks with 1200 SERIOUS WATTAGE capability,(there are 1800 and even 2,5/6/8Kw versions on the market) unscrew it, split and let them breath/cool maybe add some fan... (Im supplying 4X 7970 on 1 = one , 1200db delta ibm)
2nd check voltage and amperage on all pins for your knowledge [and do it always before adding extra power consumption unit]
3rd play with your mem and gpu clocks at least long you did it already with your girl/boy Friend

4tth its really possible to get almost 600khash on 7950 specially if you run cgminer under any debian tree distro.

5th- in need of answers pm me

this are rates for scrypt mining LTC/FTC/CNC etc

7th (don't ask where is 6th) Never trust any PSu , always open it and check main components like trafo, BIG capacitors etc.. I got bunch of shit worth, 1000 watt called psu on stickers. Don't trust stickers

8th adjusting voltage on gpu/MB in my private opinion is pointless. Let me earn some lesson if you are successful with over/under volting