Litecoin mining on Mac Pro Mid 2012

[Vinz87]

I'm trying to mine Litecoin for fun on a Mac Pro 5,1 Mid 2012.
It has 2x2.4 GHz 6-Core Intel Xeon, 28 GB of RAM, and an ATI Radeon HD 5770 with 1GB of memory.

I would like to try some fine settings but I don't exactly which could be the maximum performances.

Currently if I use cpuminer it reaches 75 kH/s binding 24 thread on the 12 cores, while the GPU only touches 3-5 kH/s with cgminer or bfgminer.

Can it do more? Especially the GPU, but keeping its usage at a level for which it is still possible to use the machine for other tasks.

Thanks

[Lauda]

The GPU should be doing much more. What settings are you using?

[Vinz87]

I don't set any parameter but the url and login. I tried some values for thread concurrency, but setting it up to 3200 (4 times shaders number) doesn't change the hashrate, while setting it higher it says to me something about too much memory required, the hasrate goes up to a meaningless number of MH/s or even GH/s and no share is found.

The memory required has nothing to do with computer's RAM? It's only about dedicated memory for GPU?

[Vinz87]

Some hint?