7990 + 7970 = strange behavior (hashrate drop)

Hi!

Added 7970 to my 7990, and *shocked*. Cards in separate PCs gives 1300+510 KH/s. Combined together in one PC, they gives me fantastic 960+540. No matter if I run them altougether with -g1 or -g2 options, or launch from different cgminers (one with -g2 for 7990, one with -g1 for 7970).

I've even lauch cgminer on separate CPU cores, but no effect.. Once I run 2nd instance of cgminer (from dirfferent folder), 7990 lost over 300 kH/s. 7970 feels OK.

Can anyone experienced point me to my errors?

commandline opts are:
SET HEADER="7970"
SET IDS= XXXX
SET OPT=--gpu-platform 0 -d 0 --gpu-fan 95 --scrypt -I 13 -g 1 --thread-concurrency 8192 --gpu-engine 1100 --gpu-memclock=1650 --no-submit-stale
start /AFFINITY e cgminer.exe %OPT% %IDS%

SET HEADER="7990"
SET IDS= ZZZZZ
SET OPT=--gpu-platform 0 -d 1,2 --gpu-fan 90 --temp-cutoff 76 --scrypt -I 13,13,13,13 -g 2 --lookup-gap 2 --gpu-vddc 1.080,1.080,1.080,1.080 --thread-concurrency 8192,8192,8192,8192 --gpu-engine 980,980,980,980 --gpu-memclock=1400,1400,1400,1400 --no-submit-stale
start /AFFINITY 3 cgminer.exe %OPT% %IDS%

Topic: 7990 + 7970 = strange behavior (hashrate drop) (Read 830 times)