Spexx! Just wanted to possibly confirm a bit of bad news for us AMD miners. It seems that when limiting single threads to single cores, we still get a drop in speed. Basically, once you go past five instances you get that drop no matter what. 7kh/s per thread up to 5 or so, then slowly drops to 5 and a bit per. Just thought I'd mention before I start digging for ways and means.
Would this be on a machine with 8 cores?
You are probably seeing a near linear increase in total hashrate as you add single-threaded minerd instances up to 5 in number, then see a drop-off in the per-thread hashrate as you add further instances. The reason for this is that the processor load from each instance is spread across 3 cores in any event (given at least 3 cores to run on).
If you run up a single instance of minerd.exe with a single thread on a multi-core machine that is otherwise idle, this can be seen using Task Manager. Once you have 5 instances on an 8 core machine, you will start to get overlap - there is no core that will be 100 percent free for a sixth, seventh or eighth instance and the instances start to compete with each other for CPU time.
While this will cause a drop in the
per-thread hashrate as you have observed, the
total hashrate obtained is optimal when you have the number of instances/threads equal to the number of processors in the machine and the CPU utilization will be maxed-out 100 percent at this point.
Deliberately restricting an instance of minerd.exe to a single core on a multi-core machine is not the best way to do it. It is very inefficient. Each instance of minerd.exe should be allocated a subset of 3 processors to run on for best performance. This applies to Intel processors as much as it does to AMD processors from what I have observed. This is why I wrote a shed load of code to handle it
