Calculating CPU need for GPU and by-question about underclocking

[BluesBrother]

Hey all!

Been reading up on these two:
https://en.bitcoin.it/wiki/Why_a_GPU_mines_faster_than_a_CPU

The simple answer is: You don't. You set affinity and run things per core.
But is it possible to calculate this?

The thoughtprocess behind the idea is a server setup of multiprocess, multicore motherboards hooked up to things like Tesla GPUs, giving enough cores for the GPUs (hopefully more than one core per GPU) and then mining with the rest.


Also curious about why some people underclock and underpower their GPUs?

Thanks.

[middlemarkal]

Hey all!

Been reading up on these two:
https://en.bitcoin.it/wiki/Why_a_GPU_mines_faster_than_a_CPU

The simple answer is: You don't. You set affinity and run things per core.for sha256 mining you don't need CPU power
But is it possible to calculate this?

The thoughtprocess behind the idea is a server setup of multiprocess, multicore motherboards hooked up to things like Tesla GPUs, giving enough cores for the GPUs (hopefully more than one core per GPU) and then mining with the rest.


Also curious about why some people underclock and underpower their GPUs? .for sha256 mining you don't need GPU RAM so you reduce it to minimum, also running colder is bettre for life of gpu card so we undervolt as much as possible at standart speed so that our cards last.

Thanks.

[BluesBrother]

Ah I see.
I thought you needed (very little?) CPU power but I read several threads telling people to attach entire cores for the GPU instead of just setting prioity for example. Are they then incorrect in thei assesment?

Quick google:
https://bitcointalk.org/index.php?topic=69445.0

[A Meteorite]

Ah I see.
I thought you needed (very little?) CPU power but I read several threads telling people to attach entire cores for the GPU instead of just setting prioity for example. Are they then incorrect in thei assesment?

Quick google:
https://bitcointalk.org/index.php?topic=69445.0

It seems that thread is someone experiencing slowdowns in GPU mining by CPU mining, so they have to set affinity for an unused CPU for the GPU miners.

You really shouldn't CPU mine. You will incur a net loss. Even if your power is free, it still doesn't really make sense (not worth the toll on the hardware).

If you're only GPU mining, CPU doesn't really matter (just get the cheapest/lowest power). My mining rig is 4x Radeon 5850s (1.4 GH/s total) on a Sempron 140. It doesn't impact the mining whatsoever. As far as underclocking the GPUs, people do it because it lowers power usage (thereby decreasing heat and increasing life). If you underclock the memory, it makes practically no difference when mining SHA256 chains. The only time memory matters is for scrypt chains (like Litecoin).

I also see your first post talks about Tesla GPUs... mining on Nvidia is pretty much worthless, so I hope you're not buying Tesla cards just to mine on them.

[BluesBrother]

Yeah you're right of course, was just a theoretical setup.
Although high end Teslas that I can''t afford could be good

Hoped that maybe someone knew a tool to easily test a potential bottleneck for GPUs without experimenting to much.
Could be used for gaming to and other stuff.


I'm reading up that it might have some value for litecoin mining though together with Nvidias system being a bit more suited aswell.
Some of the self-clocking intelchips seem to have a little effect. They would yeild you about 70 dollars a year at the current state.


Do you know any comparison-chart for litecoins?

[crazyates]

There used to be bugs where running a OCL application (like Bitcoin mining) would use up 100% CPU on one core. If you had more GPUs than you had CPU cores, this could be a problem.

Those issues have since been fixed, and you can get drivers/SDKs that do not ramp your CPU up to 100%. Since this, CPU speed is completely irrelevant. That wiki link has not been updated in a very long time.

[BluesBrother]

Cheers