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Old 2009-01-04, 10:19   #1
joblack
 
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Default hardware suggestions for a second prime95 pc?

I´ve playing to buy a second pc for additionally prime95 power.

The

Intel Pentium Dual-Core E5200

is very much overclockable (and has a good price) but has only 2 MB cache (shared).

How important is the CPU cache for the prime95 performance? Do you have additional suggestions (cheap hardware and good performance)?

greetz
jb

Last fiddled with by joblack on 2009-01-04 at 10:22
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Old 2009-01-04, 11:18   #2
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Quote:
Originally Posted by joblack View Post
How important is the CPU cache for the prime95 performance?
Above 512kb per core, L2 cache size doesn't play much role in P95 performance.

Last fiddled with by axn on 2009-01-04 at 11:19
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Old 2009-01-04, 15:45   #3
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I can't say enough about how happy I've been with my OC'd Q6600. With rebates from newegg, the system cost $360. For that I got a GA-EP45-DS3L, Q6600, zerotherm FZ-120, a cheap ASUS video card, OCZ 450W power supply, and 2GB Corsair dominator 1066MHz memory. I used an old hard drive that I had laying around, and am building the case myself (to enclose two computers). For performance, it initially ran 4 LL (47M) tests at stock speed with iteration times of 96 ms for each of 4 cores. OC'd to 3.2 GHz (and OC'd memory) it runs the same 4 tests all at 61 ms.

Last fiddled with by stars10250 on 2009-01-04 at 15:46
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Old 2009-01-05, 04:59   #4
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Quote:
Originally Posted by joblack View Post
Intel Pentium Dual-Core E5200
I've been running the E5200 on my second PC for a few months already. Overclocked to 3.5GHz with a slight voltage bump. Temps are in the low 60s. The small L2 cache doesn't make much impact on Prime95. If you think about it, 2MB cache isn't bad at all - the first few Core2 processors were 2MB.

Basically this makes a good PC for surfing, internet, office apps and even medium amount of gaming. It doesn't have virtualisation and SSE4, but the apps that need SSE4 are unlikely to the purpose of such a budget PC.
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Old 2009-01-05, 09:19   #5
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Quote:
Originally Posted by db597 View Post
I've been running the E5200 on my second PC for a few months already. Overclocked to 3.5GHz with a slight voltage bump. Temps are in the low 60s. The small L2 cache doesn't make much impact on Prime95. If you think about it, 2MB cache isn't bad at all - the first few Core2 processors were 2MB.

Basically this makes a good PC for surfing, internet, office apps and even medium amount of gaming. It doesn't have virtualisation and SSE4, but the apps that need SSE4 are unlikely to the purpose of such a budget PC.
There could have been much higher clock rate possible. It strongly depends on the build date of the cpu. Virtualisation and SSE4 isn´t supported for prime95?
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Old 2009-01-05, 16:21   #6
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Actually I can run windows at 3.8GHz and with a little more voltage. But it's not prime stable - every 3 days or so Prime95 will give an error. The PC is stable other than that (no BSOD or hanging). It's just Prime95 that pushes things a little too far.

Having read a thread about the high error rate of exponents returned in these forums, I've decided to play it safe since having a stable PC is what's more productive for GIMPS as a whole.

Virtualisation and SSE4 aren't useful for Prime95. The former is for running multiple OSes at the same time, and SSE4 is more useful for video editing - in which case a quad with 8-12MB cache would be more appropriate anyway.
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Old 2009-01-05, 16:54   #7
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Quote:
Originally Posted by db597 View Post
Actually I can run windows at 3.8GHz and with a little more voltage. But it's not prime stable - every 3 days or so Prime95 will give an error. The PC is stable other than that (no BSOD or hanging). It's just Prime95 that pushes things a little too far.

Having read a thread about the high error rate of exponents returned in these forums, I've decided to play it safe since having a stable PC is what's more productive for GIMPS as a whole.

Virtualisation and SSE4 aren't useful for Prime95. The former is for running multiple OSes at the same time, and SSE4 is more useful for video editing - in which case a quad with 8-12MB cache would be more appropriate anyway.
You have to get it prime95 stable ... just decrease the clock and/or voltage bit by bit and check again. If prime95 gets errors you will get errors in other applications as well (but you don't get it immediately because a flipped bit doesn't make much difference in a lot of cases ...
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Old 2009-01-06, 04:51   #8
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Quote:
Originally Posted by joblack View Post
You have to get it prime95 stable ... just decrease the clock and/or voltage bit by bit and check again. If prime95 gets errors you will get errors in other applications as well (but you don't get it immediately because a flipped bit doesn't make much difference in a lot of cases ...
Yeah, that's why I've brought it down from 3.8GHz to 3.5GHz in the end. No point in trying to gain a palfry 0.3GHz and in the end the whole result becomes invalid. Also, above 3.5GHz you also need to increase the voltage by quite a bit (required exponentially higher towards the end). The small increase is just not worth the risk and extra electricity too.

At 3.8GHz mine can play FarCry 2 completely stable and even pass 24hrs of torture test. The errors occur once in 3 days - not easy to catch. Googling on the net, you'll see a lot of people claim a 3.9-4GHz overclock on the E5200 is possible. It's probably fine for them to run 3DMark and game benchmarks, but it's just not prime stable.
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Old 2009-01-06, 04:55   #9
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Quote:
Originally Posted by db597 View Post
The errors occur once in 3 days - not easy to catch. Googling on the net, you'll see a lot of people claim a 3.9-4GHz overclock on the E5200 is possible. It's probably fine for them to run 3DMark and game benchmarks, but it's just not prime stable.
Some of them are valid (tomshardware.com had made some pretty hard (prime95) tests) but you have to get a good one ...
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