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Old 2008-08-08, 05:36   #1
tmorrow's Avatar
Jan 2004

103 Posts
Default Trying to Spec Up a Mid-High End System

I'm looking to buy a new number cruncher. It will be used 24/7 for trial factoring and some LL work for GIMPS. Some headroom needs to be provided to serve for other PC activities, e.g. some gaming and internet browsing etc. Naturally I'm trying to get the biggest bang for my buck in the one system. I am however prepared to pay extra for a solid, fast performer. While performance is important, stability is paramount - for example, I probably won't be overclocking. I've been reading this forum and elsewhere to help me make a decision on what are good choices for my system.

I've managed to make a couple of decisions so far but could use some input for the unknowns. My knowledge in hardware is not extensive. In fact reading some of the forum articles has confused me further.

I'm pretty much going the intel route, sticking with XP as an OS, 32 bit still - longer term I intend to move to 64 bit Linux, but not right now.

I was hoping for something like a dual processor motherboard with 8 cores (2 quad core high end cpu's?), similar to a Mac Pro, but I'm not sure this is possible without going the more expensive Xeon route. I'm really not sure what motherboard/chipset to get.

In terms of CPU's I was looking at Q6600 or above, up to Q9450 with some interest, these are in my price range.

One of my concerns is matching the memory with a quad core based solution as I've read this can be a bottleneck. Any advise on this point is most welcome. I am currently under the assumption that a decent amount (4-8GB) of fast, fully buffered DIMM's and ECC ram is advisable.

I've also got some concerns on cooling, I live in Australia which is very hot in the summer. The oem stock supplied fans are usually crap. I'm not sure what good choices are.

I'm fairly comfortable with what to get for the other system components.

Thanks in advance for any insights you can provide.
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Old 2008-08-08, 05:58   #2
Kevin's Avatar
Aug 2002
Ann Arbor, MI

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As of right now, there's no good way to get dual quadcores.

Personally, I'd go with a Q9xxx. Q6600 is definitely the best option for overclockers, but I think the price/performance ratio is a little closer at stock speeds. The Q6600 has had a price drop recently, and the prices for some of the 45nm quad cores are going to drop around August 10th when Intel releases their new line of 45nm processors. I'd wait a week or so to see where prices end up, and then look at benchmarks/prices to figure out what gives you the best bang for your buck.

I believe memory speed is more important than size or ECC vs nonECC. Having more memory really only helps in part of P-1 factoring, and at some point adding more memory only negligibly increases your chance of finding a factor. I'd recommend 2x1GB DDR2PC8500 (1066mhz), unless the 800mhz stuff is considerably cheaper (or you having other computing needs that would merit more than 2 gigs of memory). I'm not exactly sure how much of a performance gain you get by going with 1066 over 800.
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Old 2008-08-08, 09:30   #3
tmorrow's Avatar
Jan 2004

103 Posts

Thanks for your input Kevin. I'd come to the same conclusion about no ready dual quad cores. That's ok, I'll get a Q9*. I tend to stay away from overclocking. The shop I'll probably buy from told me about Intel's up and coming new quad cores and price adjustments and told me they would factor that into their quote.

Good insights into the memory situation. It's been confusing me for a while. I've earmarked PC8500 but as to how much I'm not sure. I want to go to 2x2GB PC8500 if I can get the OS to see all 4GB. At this point I was limiting myself to XP Professional 32 bit. If that OS locks me into less memory I'll reconsider. I don't want to go to Vista though. My long term plan is to give Billy Gates the flick and get onto a Linux or Mac platform. The only thing holding me back is lack of knowledge of Mac's and lack of gaming support on Linux.

Most of my factoring work is Trial Factoring to n bits, some ECM (GIMPS and Non GIMPS) and some MPQS on remaining cofactors up to 100-110 digits. I was looking to trying out some NFS with the new machine, which has some large memory requirements at certain points.
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Old 2008-08-08, 11:02   #4
ATH's Avatar
Dec 2003

61508 Posts

In Windows XP 32bit you can only use around 3.2Gb RAM.
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Old 2008-08-08, 11:44   #5
tmorrow's Avatar
Jan 2004

103 Posts

I've heard that roughly 3.0 GB is usable in 32 bit XP, but then I've also heard there are switches to enable it to work for larger memory configs for some systems.

My understanding is that a 32 bit OS can virtually address 2^32=4GB, but the hardware, software, and OS kernel all require address reservations (even if they aren't actually using any space in RAM or swap at any point in time).

The upshot is that depending on your hardware, you might only have 3GB or so available. Unfortunately I've heard that motherboards with PCI Express take the worst hit - which is what I'll be getting.

I understand that there have been switches developed to get around the memory problem like /PAE (developed by Intel) and /3GB. I haven't explored under what circumstances these switches can be used and prove useful, I believe they aren't supported by all motherboards. In fact the /PAE switch on first inspection would not be good for number crunching apps like GIMPS and the /3GB switch cannot be taken advantage of unless the app is specially written. I see these switches as hacked workarounds to a problem that can only properly be resolved with a 64 bit OS. Unfortunately in my estimation, the 64 market is still very immature in terms of application support and I'm not ready to take that plunge yet.

I guess I'm just trying to decide whether 2GB will be sufficient for me or whether I should go up to 4GB to get an extra 1GB. I'm on the fence with this one.
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Old 2008-08-08, 13:09   #6
bsquared's Avatar
Feb 2007

67728 Posts

Originally Posted by tmorrow View Post
Most of my factoring work is Trial Factoring to n bits, some ECM (GIMPS and Non GIMPS) and some MPQS on remaining cofactors up to 100-110 digits. I was looking to trying out some NFS with the new machine, which has some large memory requirements at certain points.
You can do a lot of useful NFS work with 2GB memory. For instance you could probably complete factorzations up to about 130 digits with GNFS, or up to about difficulty 220's with SNFS (my recent work on 10,339- required 1.5G at its most memory intensive stage, difficulty 229), using currently available public software.

If you just want to contribute to larger factorizations, for instance here:, then 2GB is plenty for the sieving portion of NFS.
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Old 2008-08-08, 13:16   #7
rx7350's Avatar
Feb 2006

24×32 Posts

Definitely use a motherboard with Intel chipsets, rather that nVidia. Iteration times on LL tests are much lower. The memory will only run at twice the FSB anyway, so unless you overclock, or set up a memory divider, PC8500 (1066Mhz) is probably a waste. If your memory is actually running at less than stock speed, consider tightening the timings to less than stock.

Do consider overclocking a small amount, 10% or so, and running a memory divider to push your memory to stock speed (and beyond) - PC8500 utilized in this fashion would not be a waste. It will decrease your iteration times significantly, making your memory running faster, is really quite simple if you have a motherboard BIOS that allows it, and doesn't really stress the hardware components that much. It will, however, void the warranty on your 'parts', but the chance of failure due to overclocking is quite small.

For your gaming interests, as well as fault tolerance of the whole system, consider setting up a RAID10 array (hard drives). This level of RAID will improve system speed because it will have two hard drive head-disk-assemblies (HDAs) reading/writing at the same time (RAID0), as well as two additional to make a redundant copy of your entire system (RAID1). To set up this array would require a minimum of four hard drives of exactly the same type. You would need a motherboard with a chipset and controller to allow using RAID, but they are quite common on mainstream mobos. A 'nice' RAID10 configuration would be four 250Gb hard drives with 16Mb caches. This would allow a 450Gb partition, with a small amount left to set up another partition if necessary. The nice thing about RAID10 is that if a single hard drive fails your system would keep running, and it could have two hard drives fail (depending on which two failed) and keep right on running.
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Old 2008-08-09, 15:39   #8
MrOzzy's Avatar
Apr 2008
Antwerp, Belgium

3·19 Posts

Originally Posted by tmorrow View Post
... and lack of gaming support on Linux ...
Maybe use vmware to run your 32 bit win Xp in a linux virtual host. It will cost you some preformance, but current games are all about gpu power and not cpu power.
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Old 2008-08-09, 22:02   #9
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fivemack's Avatar
Feb 2006
Cambridge, England

3·19·113 Posts

I tend to think of low-end as the cheapest thing that does the job, mid-range as the fastest thing that fits in your budget, and high-end as things you can't justify buying ...

Use a 64-bit OS, or at least be prepared to boot into AMD64 Ubuntu for big NFS matrix-build jobs: it's so much easier when you don't need to worry if a job fits in address space. Unless you are unusually patient, any NFS job where you can endure the runtime will fit on a 4G machine with sufficient swap; there's no point in getting less than 4G nowadays.

If you can wait until Christmas, it looks as if Nehalem will be worth the wait, though 6GB of fast DDR3 is still quite an extravagence.
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Old 2008-08-10, 00:38   #10
Batalov's Avatar
Mar 2008

100101011000112 Posts

If I were to build a new system now, I'd start looking at the 1200MHz DDR2 (when I was building inDecember, 1066MHz was just on the verge of becoming comodity, now 1200 is probably in the same place, 1066 is a bit passe, and don't even think about 800)
or DDR3, of course, if you can afford it. In my opinion, ECC is not entirely necessary (and expensive).

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Old 2008-08-10, 16:22   #11
dsouza123's Avatar
Sep 2002

2·331 Posts

For the windows swap file (or maybe fast storage)
use a Compact Flash DIY SSD with SATA/IDE connectors
from Century or Raidon, they use the CF in various RAID modes.

An 8GB compact flash card is about $35,
the DIY systems use either 1, 2 or 3 CF cards.
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