Mining issue

[zxcvbrna]

I have managed to get everything figured out and working but one problem.

I have a rig that has
4 7870 Tahitis
http://www.newegg.com/Product/Product.aspx?Item=N82E16814131484

MoBO
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128521

1300W PSU
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182063

8 gigs of ram

CCC 12.8

All risers are powered. and every video card has a dummy plug (I have swapped the dummy plugs just in case one was bad)

runs on windows 7 pro 64bit using CGminer (newest version).

All 4 cards are running smooth. I am able to get them to mine sha256 526 MH/s.

But when I try to mine scrypt card 1 and 4 only will get around 250 KH/s and 2-3 get around 420KH/s

Card 1 is pcie-1x and card 4 is pcie- 4x. Card 2 is PCIE-16x and card 3 is PCIE-1x

I have checked the mem/core clocks with gpuz to verify that the cards arent being throttled. I have tried all versions of ccc from 12.1 and newer. They are all running the same settings in one instance of cgminer. I have searched for hours for this issue. I have given up searching and hopes that some one has the answer here. Any ideas?

[silebe]

Sell it and buy ASIC miners ?

[sabahgamemaker]

ASICs will be even worse; coins using scrypt algorithm have RAM overhead which will overwhelm the ASIC. That's why there are no ASIC for scrypt based cryptocoin like Litecoin

[Yna]

Have you tried changing the cards locations? It could be faulty cards

[drpepper7]

Sell it and buy ASIC miners ?

+1

[xide]

what clock are your gpu's?if your video ram is dowclocked that is reason getting 250kh/s


you must know that scrypt mining (alt coins) are 1000 lower speed and it is in KH/s
scrypt mining is also using your v ram...if your ram is downclocked that is bad for mining speed...
so gpu/mem ratio is about 0.7 that means if your gpus is on 1000mhz your video ram clock has to be almost 1500mhz if you want good hashing rate power...

try gpu on 1000-1000mhz ram 1375-1500clocks to see what value you get?

and what program /pool/coin your are using ?



example (ati 6970 in sha 256 -bitcoin has speed 400mhs/ but in scrypt gets almost 495kh/s )
if you have some questions and need help skype me...

dejan.arandjelovic86

[zxcvbrna]

The memclock on the gpu is 1500 and the core clock is 850. all 4 cards are in the same rig, mining in the same pool, multipool.in

I have tried different scrypt coins and the same results with all. The program is cgminer.

My issue is I have 4 of the exact cards in the same machine mining the same coins but 2 of them are slower. I swapped out the slower cards with brand new cards, same issue. I changed which slots they were an and then only 2 cards were slower but it wasnt the original 2 slow cards but it wasnt the slower slots either.....

So I cant find any consistency in my problem. I know its not a bad video card. I know its not a bad slot...
Its not the clock settings since 2 of them run at the right speed with the same settings. I even went so far as to upgrade of their bios to the same bios. Still having the same issue.