I agree except for the part about i7's running cool. I thought that too but was informed that even the new D0 (E0 for Xeon) stepping still runs quite hot - around 60C and higher on stock cooling and full load - IIRC (which I may not).

However there is a big difference between an i7 920 and a 965 - in price, performance and overclocking potential.

Xeon, as you probably know are server chips and therefore more expensive - even though the basic architecture is similar. Plus there is then the issue of getting single socket, dual socket or quad socket models.

After processor IPS (instructions per second) and clocks (3.2ghz for the 965), everything else is a distant second. 2 gig should be plenty of memory if you only intend to run boinc and memory speed and timings aren't going to make enough of a difference to justify getting super fast/tight memory.

Running the extra threads on an i7 really do make a difference and make it far and away the first choice for crunching.

edit: IPC not IPS - instructions per cycle.

edit 2: If you are going to use the computer for other things and you don't want to spend $280 for a 920 (or $1000 for a 965), you can get a 3.2ghz Phenom II X4 for less than the 920 (at 2.66ghz) and it has an unlocked multiplier so you can squeeze every last clock cycle out of it. Getting it to run stable at 4ghz and above is pretty common. Of course you only get one thread per core rather than 2 so the performance might be as much as 1/3 less than what you would get at stock speeds from a 965.

May I correct the statement regarding RAM?
If you plan to run 8 boinc threads (hyper threaded i7): you need much more than 2 GB RAM.
Since two years, I run 8 boinc threads on a boinc devoted double Quad Xeon and I noticed with the last three new projects (HFCC, IADS, and especially HCMD-2) that the memory use goes over 2.3 GB. Previously with HCC, the average memory use was between 0.9 GB and 1.3 GB.
For this reason, you should plan at least 3 GB better 4 or 6 if you additionally plan to work with the system (running more applications).
In such case, you have to consider to prefer a 64 bit operating system because the crazy 32bit windows (incl. Vista) is only able to recognize around 3.5 GB memory (even is much more memory is installed).
If i7 seems too expensive for you, Q9450 is still a good (and less expensive) choice with 4 threads.
Happy crunching,
Yves

I am not selling anything :-)

I have an i7 running 8 threads. What I have observed (no scientific study) is that whenever I check I am never above 3 GB ram in use (I have 6 in Vists 64). Right now I am have 3 FLU and 5 HCC at 1.78 GB ram (plus all other stuff like antivirus, fire wall, browser, etc.). If I were to build another crunching unit ... I would try to balance crunching power/ initial cost/ on going electricity cost/ heat - yes, running a computer 24/7 under full load generates a fair amount of heat.

CPU: i7 920 - make sure this is stepping D0, or just buy the WS3520 which is basically the same chip (it can use ECC memory) and pretty much all the x58 motherboards support both.The reason for suggestng the D0 stepping or WS3250 is that if you are going to overclock (OC), they typically require less volts and OC higher (neither by very much but every little bit counts) than the standard i7 920 stepping C0. (I have the standard i7920 C0 stepping and it works fine).

Motherboard (MOBO): I have the low end ASUS P6T and I have seen the low end Gigabyte suggested also. As you research MOBOs you will find lots of very expensive toys and some very passionate people. At the end of the day the more expensive boards are best suited for people who are into extreme OC (not what we are talking about here).

Heatsink/Fan (HSF): If you intend on OC you will need to buy an after market HSF because the stock unit was designed for stock speeds, it can't handle the extra heat OC produces. There are lots of brands and models to choose from. The Xigmatek 1283S is pretty good for a decent price, many like the True but they are more expensive.

RAM: I would go with 3 x 1 GB sticks. For an i7 you always want to go either 3 or 6 sticks to take full advantage of the triple channel support. For crunching the speed is less important and timings even less so. Either 1333 or 1600 will work great, find something on sale :-)

Harddrive (HDD): I would seriously consider one of the new Solid State Drives (SSD). While they are initially more expensive (quite a bit) they use so much less power and are so fast I don't think I could resist. This standpoint is more personal that crunch cost wise as a traditional harddrive will work just fine. I would probably end up going for a slower, more energy efficient model like the WD Caviar Green.

Power Supply (PSU): For a crunching only PC I would suggest something in the 450 Watt range. Corsair makes good power supplies, many other companies do also. Don't cheap out on this, you need to keep your CPU well fed and an efficient PSU will help keep you electricity bill down and generate less heat.

Video card: You may not want/need one at all which will help keep the electricity bill down. Yes, you will need one to set the PC up but you should be able to pull it out once you are done and then manage the machine remotely. If that sound a like too much for you right now then go with the smallest, cheapest video card you can find.
If you are going to use this as your regular machine just keep in mind that the more powerful your video card, the more electicity it will use and you will also need to get a higher rated PSU.

Come on over to ExtremeSystems
http://www.xtremesystems.org/forums/forumdisplay.php?f=207
There is a section specifically for World Community Grid (WCG) where we discuss, joke, have fun, talk about crunching. We would be more than happy to help you complete a build and get it crunching :-)

Hi Sekerob,
indeed I was surprised by my last observations regarding memory use.
It is a remote host, so I don't have opportunity for "daily" observations. Anyway, after more than one year using between 0.7 and 1.2 GB (e.g. by running some CEP WUs of the first generation), I notice during the last weeks that the host is now using regularly more than 2 GB (average 2.3 GB) for boinc computing eight WUs at the same time. Because the system has 4 GB RAM (nonetheless pretty few for a 8 cores system) I don't experience any troubles. However I think that this observation should be taken into account by specifying a new crunching machine.
Cheers,
Yves