Title: Strange 7970 tweakage Post by: Jazkal on May 30, 2013, 09:57:39 PM I have a very strange (to me) thing going on with my 7970's. Let me start off with some of my hardware\OS\driver stats:
OS: Win7 x64 GPU's: Sapphire 7970 OC - (11197-03-40G) (http://www.amazon.com/gp/product/B009B6Y01Y) RAM: 8GB AMD Driver: 13.1 SDK: 2.7 I have gone through all the threads that discuss getting the 7970 running optimized for Scrypt mining: 1) https://bitcointalk.org/index.php?topic=117221.msg1256502#msg1256502 2) https://bitcointalk.org/index.php?topic=173938.0 3) https://bitcointalk.org/index.php?topic=28402.msg1635964#msg1635964 4) and many others, but those are the main ones. So just using stock voltages (don't want to mess with tweaking those), I was able to determine by highest stable memory settings for me are 1625. I ended up using these settings to allow cgminer to find me some good numbers: cgminer.exe --scrypt -o stratum+tcp://pool.com:3333 -u Jazkal -p X --intensity 13 -g 2 --thread-concurrency 8192 --lookup-gap 2 --gpu-powertune 20 --auto-fan --auto-gpu With this, I was able to boost my numbers from low 525 or so to 630-650. Looking at what cgminer defaulted to, it choose 950/1625. Sometimes if would choose 1650 which would crash the system. So I tweaked around and found that 1650 was the outside edge of stability for this card. So I added a hard code for 1625 which seemed to run just fine and was stable. Now since I run my rigs out in an outdoor shed in the middle of the Texas summer heat (100F+), I let cgminer change up my settings downward when the heat climbs. So I was adding in this setting: --gpu-memclock 1000-1625 This is what I find strange... And when I re-launched cgminer, it defaulted to 950/1000 but was still running at 630-650 stable. Why would it run at the same hashing power at 950/1000 and 950/1625? This doesn't make any sense to me. Can someone help me understand why this is? I thought Scrypt mining was all about super high memory settings. edit: forgot to add my driver and sdk info Title: Re: Strange 7970 tweakage Post by: Nemo1024 on May 30, 2013, 10:25:22 PM I remember the scrypt readme saying that higher memclock does not imply higher hashrate. The relation between memclock and gpuclock are more important.
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