Topic: A 7970 Scrypt mining observation. (Read 635 times)

Hi all,

first n00b post so sorry if this has been picked up elsewhere...

I have seen a LOT of people having serious issues hitting a decent hash rate with cgminer and scrypt on 7970 cards especially newer models, (~550Kh/s) some people have partly overcome the issue to 650Kh/s with bios flashing and others with extreme or odd mining config files with odd "thread-concurrency" settings, modded kernel files and underclocking.

Having tested several different cards from Sapphire, Gigabyte, MSI and XFX I have come to the conclusion that the main issue preventing these cards from hitting the magic 700+ Kh/s is the "gpu-threads" configuration. For some reason (and I can’t figure out why) on some setups this defaults to 1 instead of 2. I have also seen that pretty much every single thread discussing the issue has plenty of different configuration settings but "gpu-threads" remain mostly untouched.

When this happens regardless of your GPU, VRAM speed, "thread-concurrency" or "worksize" you will see the 550~650Kh/s speed range.  For anyone with issues getting a decent hash rate on a 7970 (and Tahiti LE 7870 XT!) give it a go, set the "gpu-threads” to 2 manually and see how you get on with the most common settings people suggest which is:

--intensity 13 --thread-concurrency 8192 --worksize 256.

I have found that all cards I can now hit 700+ Kh/s and as it uses an intensity of 13 the desktop remains usable too!  For an extra speed boost when running two gpu threads is to use a “thread-concurrency” of 8191 for an extra 20~ Kh/s and OC the ram to 1500MHz for an even bigger boost.

I understand that Scrypt mining can be a fickle beast and I know this won’t work for everyone but I hope this helps someone stuck with a newer card thats under performing and if anyone else has any tips or hints that might help out with Scrypt on a Tahiti LE I'd be grateful for input. Thanks for reading.