Cheapest CPU cycles?

[nucleon]

Originally Posted by siegert81

Some questions:

1. Is the 1 GB GPU necessary or just better than the 768 MB GPU?

Most of the time it is faster. (depends on code used)

1GB has wider memory bus, which yields better memory throughput. A lot of the comments in the GPU forum are pointing that some of the code out at the moment is memory throughput limited and not raw flops limited.

The tesla based cards aren't benching much faster than the consumer cards even though they have more dp fp units enabled.

-- Craig

[Ken_g6]

The first thing you should do is pick a range that you plan to finish. Depending on your sieving program it may be worthwhile to sieve more, but start by considering a practical range.

Next, consider that in a properly arranged personal prime search, sieving shouldn't take very long. I'd guess about 1-4% of your time will go to sieving. You want to search for low K's, so your range will likely be a candidate for using PPSieve. But also recall that there is a multi-threaded CPU version of PPSieve. So I wouldn't recommend getting a GPU just to sieve for a personal prime search.

On the other hand, a GPU LLR application may come along soon. Then again, we've been saying that for months. A GFN GPU app is now working, if you want to go that way instead. Otherwise, I'd suggest just getting the CPU and onboard graphics, and waiting to get a GPU until a GPU LLR appears.

[rajula]

Originally Posted by Ken_g6

- - So I wouldn't recommend getting a GPU just to sieve for a personal prime search. - - Otherwise, I'd suggest just getting the CPU and onboard graphics, and waiting to get a GPU until a GPU LLR appears.

I agree with Ken_g6.

If you decide not to buy a good GPU now, it is probably wise to build a computer which allows you to add the GPU later without changing other parts. You will need a good PSU when you are using GPU(s). Also some of the smallest cases could be too small for the GPU(s).

[cheesehead]

siegert81,

Don't overlook rajula's comment about PSU! All that fast processing in one of these GPUs requires a lot more power than old GPU picture drawing did. Check yours for sufficiency!!

[fivemack]

I would be very tempted to wait a month, it looks as if the Sandy Bridge parts are much cheaper than people were expecting and really quite fast.

Do think of power costs if you're getting something with GPUs in; a GPU costs about as much in electricity each year as it did to buy in the first place, whilst a computer takes about three years to use one computer-price in electricity.

[siegert81]

"A GFN GPU app is now working, if you want to go that way instead."

Where can I download this application?

Also, I'll need a new PSU for about $100. However, a graphics card would be nice for StarCraft 2! So I may get a GPU and a new PSU in 2011.

I've done more research on GPUs. They are interesting. Are they going to take over the functions of the CPU in the future? Are GPUs a threat to Intel?

[Ken_g6]

Originally Posted by siegert81

"A GFN GPU app is now working, if you want to go that way instead."

Where can I download this application?

This thread, page 2, or page 3 for Macs.

Originally Posted by siegert81

Also, I'll need a new PSU for about $100. However, a graphics card would be nice for StarCraft 2! So I may get a GPU and a new PSU in 2011.

I've done more research on GPUs. They are interesting. Are they going to take over the functions of the CPU in the future? Are GPUs a threat to Intel?

Make it an nVIDIA, since the GFN GPU app is only written for nVIDIA right now. GPUs are like floating-point math coprocessors used to be. You can run these things on a CPU, but a GPU is faster. The most irritating thing right now is that languages are not consistent across GPUs, except that most are supporting OpenCL, slowly. Sandy Bridge will support OpenCL, hopefully more efficiently than AMD GPUs do right now.

But for now, I would say more GPU apps are written in CUDA (nVIDIA's proprietary language) than in OpenCL. nVIDIA GPUs can also use OpenCL, so they seem like the best choice for now.