Dedidicated rig; What counts in Prime Crunching?

[kaffikanne]

Hi

I want to build a cheap system solely for GIMPS. And I was wondering what to prioritize. The CPU is as i understand important. But what about the other components.

I have been looking around this site to see CPU benchmarking:
http://mersenne-aries.sili.net/throughput.php

Processors I could choose:
AMD Athlon II X3 435
AMD Athlon II X4 620
Intel Core 2 Duo E7400

Could i cut cost without affecting the CPU performance by reducing:

DDR memory: How much is enough, does clocking speed matter, is there a difference between DDR2/DDR3?
HardDrive: Would it be feasible to use a USB-Pen as the sole storage for operation system/prime95?
Motherboard: Should one go for the Cheapest, or is there an advantage in a good/expensive motherboard?

This system is just for Prime95 or similar GIMPS software. I am not searching to get the "Ultimate" system, just the ultimate Bang-for-the-Buck." It seems that the best CPUs require expensive Motherboards, and DDR memory to reach its full potential. Am I mistaken in this belief? Also: I live in Norway, so electricity is very cheap.

Would love to hear your feedback:)

[joblack]

Athlons are around 10 % slower than Intel Cores with the same speed. More than 2 GByte isn't needed (I've got 8 GByte and one of four threads is a 100M number).

You might need more memory for factoring but LL isn't that hard ..

[fivemack]

You want the X4 620, 2G of DDR3 memory, a USB stick for disc, and the cheapest motherboard-with-internal-graphics that supports the X4 620. Run Linux; ubuntu-9.10 is probably easiest.

(Core2 may be faster per core, but the X4 has twice as many cores)

[petrw1]

More discussion on options in the "Need help deciding between ...." thread in this same hardware forum.

If you can define "cheap" as up to $600 you can get the i5-750 discussed there. It seems to be quite popular. Three of us identified getting one in the last month.

[nucleon]

if you can wait....

Best machine for the money is looking to be a core i5/i7 with a nvidia 3xx series vid card (when they get released, ETA=early next year).

A Nvidia 260GTX is looking to have about the same throughput as a core i7 920 ish on it's own. A 3xx series is looking to be 4x this throughput.

-- Craig

[cheesehead]

Question for you veterans:

It seems to me that memory bandwidth is the most important single factor besides CPU speed. (It's also the factor I've always forgotten to consider when buying a new system. E.g., I completely overlooked that the last motherboard I bought for a dual-core had only single-channel memory access.) Prime95's inner FFT loop has several stalls waiting for memory transfers.

How much do the various components, including motherboard, affect memory bandwidth?

[ldesnogu]

Originally Posted by cheesehead

How much do the various components, including motherboard, affect memory bandwidth?

The last generations of CPUs (Intel i5/i7 and all Athlon for years) all have an embedded memory controller, so the motherboard should have minimal impact there. The only differences between MB will be better capacity to overclock the RAM modules and keep the beast stable. Also some default settings in the BIOS may slightly alter timings.

If you read this:
http://techreport.com/articles.x/17789/5
you'll see for instance that all of the P55 motherboards have very close performance numbers.

[nucleon]

Originally Posted by cheesehead

Question for you veterans:

It seems to me that memory bandwidth is the most important single factor besides CPU speed. (It's also the factor I've always forgotten to consider when buying a new system. E.g., I completely overlooked that the last motherboard I bought for a dual-core had only single-channel memory access.) Prime95's inner FFT loop has several stalls waiting for memory transfers.

How much do the various components, including motherboard, affect memory bandwidth?

The Corei5/i7 platform has a significant increase in memory throughput. From reading the forums, that it appears the quad-core cpus on Core2 platform get saturated memory throughput at about 3x LL tests. Whereas quad-core cpus on Core i5/i7 platform are quite happy with 4x LL tests.

For more core2 system it gets around 4GB/sec mem throughput, and my core i5/i7 system gets around 10GB/sec.

-- Craig

[cheesehead]

Thank you, ldesnogu and Craig.

[Bectkeync]

SOUND CARD

i gauranttee however its spelt that you will get a niiice increase in FPS if you upgrade your SC to a SB128 or Live

The soundCard you have is SOO SLOW that it is holding your NIIIIIIICE rig back from its true Potential

[joblack]

Originally Posted by Bectkeync

SOUND CARD

i gauranttee however its spelt that you will get a niiice increase in FPS if you upgrade your SC to a SB128 or Live

The soundCard you have is SOO SLOW that it is holding your NIIIIIIICE rig back from its true Potential

Not right as long as you don't use an ISA card.