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Old 2009-09-08, 21:53   #1
Prime95
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Default Help building new computer

I'm going to build a new computer. Its main purpose will be for optimizing prime95 before being relegated to crunching. Suggestions welcome.

I'm thinking the 1156 socket rather than the 1366 as that will be more the more popular platform (alternatively, I could get a socket 1366 and only populate 2 dimms to simulate the 1156 memory bandwidth). I'd like hyperthreading, just to see if we can't somehow put it to good use.

I'd like to overclock it modestly. I'd like to save money where possible. My proposal thusfar:

i7-860 ($300): http://www.newegg.com/Product/Produc...82E16819115214
Gigabyte P55-UD3R motherboard ($140): http://www.newegg.com/Product/Produc...82E16813128401
OCZ 4GB DDR3-1600 ($49): http://www.newegg.com/Product/Produc...82E16820227342
1TB disk ($95): http://www.newegg.com/Product/Produc...82E16822136284
cheap video ($33): http://www.newegg.com/Product/Produc...82E16814127366
cheap DVD ($28): http://www.newegg.com/Product/Produc...82E16827106281

Total $646 - I think there are some combo deals that will shave $20 - $30 off that total.

I've not been following this stuff closely to know which are the better brands these days.

I still need case/power supply. Might need a CPU cooler, too.
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Old 2009-09-08, 22:09   #2
Prime95
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Uh oh. Memory has to be 1.65V. Back to the newegg website....

4GB memory ($95): http://www.newegg.com/Product/Produc...82E16820231279

Last fiddled with by Prime95 on 2009-09-08 at 22:10
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Old 2009-09-08, 22:39   #3
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That all seems very sensible. The i7/860 will almost certainly come with a CPU cooler; I found that the one Intel supplied with the i7/920 that I bought in January was rather underpowered (I was getting thousands of thermal interrupts a second), and bought a chunky Zalman cooler since which the machine has not recorded a single thermal interrupt.
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Old 2009-09-08, 23:05   #4
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It does look good; I was just pretend-playing with a similar rig (don't want to buy yet). The 860 is just out, great timing.
Very good catch about the memory voltage, too.
Agree about Intel stock coolers, they were always p.o.s.
I've got a Tuniq Tower for the q6600, and his cousin Sunbeam CCF-120 for the Phenom (because it attaches right, unlike X1283), but there's a lot to choose from.

Rotten tomato count 0.
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Old 2009-09-09, 00:26   #5
Prime95
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A question for an i7 owner: Will 4 LL workers of prime95 saturate two DDR3 memory channels? An i7-920 setup will cost maybe $30-$50 more.

I can pull one DIMM and optimize prime95 for that memory bandwidth. When I turn it into a cruncher box, I can put the stick back in. Of course, this only makes sense if the 4 workers can use the extra memory bandwidth. If not, I'll save a few bucks with the i7-860 setup that also runs on a little less power and generates a little less heat.
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Old 2009-09-09, 04:28   #6
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Quote:
Originally Posted by Prime95 View Post
A question for an i7 owner: Will 4 LL workers of prime95 saturate two DDR3 memory channels?
how exactly would one be able to tell? what are the signs and symptoms?
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Old 2009-09-09, 06:07   #7
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You would have to run 4 LL workers. Jot down the iteration times for each worker thread. Shut down the machine, yank out a dimm. Reboot and run prime95. Again jot down the iteration times. Post the timings. Shutdown, reinsert dimm, reboot.

Yeah, I know that's a pain
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Old 2009-09-09, 08:58   #8
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You would get the most out of a 1366 socket set-up. It should be able to use 2 memory channels only for optimising 1156 sockets, but you would be able to optimise for 1366 sockets as well. I think, without experimental data I must admit, that even with the i7 architecture, memory bandwidth will be a key factor (especially if you take possible hyperthreading into account.

I find that all articles about hardware tend to focus on gaming and productivity applications and depreciate memory bandwidth (for instance for the Core2 Quads, the recommendation from a lot of articles was to use 800 MHz memory....) For Prime95 I have always seen a better throughput with faster memory.

Jacob
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Old 2009-09-09, 10:43   #9
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Quote:
Originally Posted by Prime95 View Post
A question for an i7 owner: Will 4 LL workers of prime95 saturate two DDR3 memory channels? An i7-920 setup will cost maybe $30-$50 more.

I can pull one DIMM and optimize prime95 for that memory bandwidth. When I turn it into a cruncher box, I can put the stick back in. Of course, this only makes sense if the 4 workers can use the extra memory bandwidth. If not, I'll save a few bucks with the i7-860 setup that also runs on a little less power and generates a little less heat.
With dual channel 1600 MHz DDR3 RAM, the memory bandwidth is 25,600 MB/s.

At the fastest stock QPI speed (6.4 GT/s), the bandwidth in each direction is 12,800 MB/s, for 25,600 MB/s total.

So I don't believe that a third DIMM will have much of an effect in terms of transfer speed, as the bottleneck is the QPI. Unless there's overclocking involved of course.

I do not believe the LGA 1156 boards have a QPI for memory access, and therefore the memory access speed for those chips is reduced still further.

I would suggest getting an LGA 1366 system, because you can always take out RAM and/or downclock the RAM to simulate reduced memory access speed. You can also disable hyperthreading on the i7 chips if you like in BIOS to simulate an i5, and even disable some cores to simulate an i3 (this is probably true for the LGA 1156 i7 chips too).
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Old 2009-09-09, 11:05   #10
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The QPI is for the processor to communicate with other processors and with the chipset; the memory on the i7 is attached via an entirely different set of pins, so the QPI speed is independent of the memory speed. The LGA1156 chips don't have QPI at all - they have about twenty PCI Express lanes instead - but this has nothing to do with the memory speed, since again the memory controller is on the CPU.
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Old 2009-09-09, 13:46   #11
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Anandtech has a nice article on Intel's new Lynnfield CPU http://www.anandtech.com/cpuchipsets...oc.aspx?i=3634.
Ars Technica has a really nice article on Apple's new Snow Leopard (10.6) operating system http://arstechnica.com/apple/reviews...-os-x-10-6.ars.
Ars Technica also has a short little article on the OpenCL programming language that is being developed by the Khronos Group http://arstechnica.com/apple/news/20...-the-block.ars.
The reason for mentioning these articles is the CPU/GPU merger that, IMHO, is accelerating very quickly. Intel is planning to have a CPU and a GPU on the same socket in the near future and Lynnfield is proof of that. Your I7-860 is a better choice than the I7-920 because of the 16 PCI-e 2.0 lanes it includes on the CPU core. You should also, IMHO, look into getting a Nehalem-based Mac Pro with Snow Leopard so that you can experiment with Apple's new "Grand Central Dispatch" feature for sharing the workload between CPU and GPU.
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