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Dual and Quad Xeon PCs
Malakai - Jan 26, 2005
  Malakai Jan 26, 2005
I'm possibly interested in building a dual or quad xeon PC, but I was wondering what type of performance increase I would get with one. A long time ago, I was considering building a dual processor system, and was told that each extra CPU only adds appx 40% to performance, and then the applications, operating systems, and games would have to support multiple CPUs to take advantage of it.

For the most part, I'm not looking to build it for games, but maybe for windows 2003 server or linux.

I'm guessing that XEONs are 64 bit processors as well, because they go past the 4gb memory limit (saw one on ebay with like 18gb ram)

Also, I see a lot of used motherboards on EBAY, and most of them say "VRM not included". Is this something that you have to have to make it work?

Anyway, any info is appreciated! thanks

 slinga Jan 26, 2005
I don't think it's a good time to get a dual or quad machine. I was thinking along the same lines as you but I decided to wait until dual core cpus come out. The other thing that detered me from building a dual cpu machine was the fact that I didn't see any mobos on newegg that supported more than one CPU.

 Curtis Jan 27, 2005
For serious apps (2003, Oracle, SQL Server, etc), yes you'll get some nice performance increases. A quad server board will cost a shitload, even doubles are expensive. I can't comment on performance - it'll change per application - but the applications still need to support multi-processors.

Xeon is not 64-bit. I'm not even sure that Intel have released their x86-64 extensions yet. Itanium is Intel's 64 bit platform, but you can't afford it.

What are you planning to do with this server anyway?

 Scared0o0Rabbit Jan 27, 2005
I run a dual athlon board. I must say programs tend to run about the same as they used to... individually. The biggest change you notice tends to be that you can run more programs at once.

Now on windows atleast, can't really speak for linux as I've never run linux on this box, if a program doesn't support running in SMP mode it will split the task equally among the cpus. What you end up with is a program running at 50% on each cpu instead of 100% on one or the other (assuming the program normally used 100% cpu).

Also on the performance, since all code needs to pass through both cpu's (unless you set an affinity to a certain cpu for the program). The fact that the 2 die's aren't on the same cpu and are further apart will actually lower your overall performance in some ways. For instance, gaming on an SMP board is really considered to not be a very good idea because of the delay between the 2 cpus.

Another thing to consider is that atleast with amd boards, cpu 2 tends to run hotter than cpu 1, and between the 2 cpus you do end up with quiet a bit of heat to deal with. I'm going liquid cooling soon (as per my dangerdenstore.com post), while it's possible to go air cooling on an SMP machine, you'll need a pretty beefy setup. I tend to idle in the 40's celsius when my room is 70-80F with my current cooling (Thermalright SLK900A's with panaflos).

A final downside I'll note is that many SMP boards require registered memory to work in any slot past the first one, which is VERY expensive compared to normal ram.

Even with all these downsides I've noted, I will say I get very frustrated using a single cpu system these days. I don't know that I'll ever willingly go back to a single cpu setup in a desktop pc again.

Hope this helps you make your decision.

Edit: oh and on another note, you might check overclockers.com they have a very good guide on setting up and building smp machines, as well as many people who can give you a knowledgable opinion without getting hopped up over whether you're choosing intel or amd.

 Curtis Jan 27, 2005

  
	
	

		
		

			Originally posted by Scared0o0Rabbit@Thu, 2005-01-27 @ 07:20 PM



What you end up with is a program running at 50% on each cpu instead of 100% on one or the other (assuming the program normally used 100% cpu).




[post=128472]Quoted post[/post]


That doesn't make much sense to my mind - programs not optimised for parallel execution cannot be magically "split" into two processes. What I'd guess was happening would be some unrelated backgroud Windows processes are being run on one CPU, while the other deals with the main program execution. That or Windows incorrectly reports CPU usage with single threaded applications running on a SMP setup.

 Malakai Jan 27, 2005
I honestly don't know what I'd do with a dual or quad CPU setup. That really makes a lot of sense eh? Let me just clear two things up right away though. I don't plan on getting the new p4 xeon CPUs, but I was thinking intel, not amd, something like two or four P3s, on used equipment.

After looking on EBAY at a lot of XEON CPUs, motherboards, etc, I figure it would cost around $300 to build, using mainly used equipment. I'm interested in trying both windows 2003 server, sql, and linux. Most likely, I would run linux in the end on it. I'm not looking for it to be a powerhouse. It's just something I have not worked with yet, true servers, not desktops running apache, ftp, or telnet daemons lol.

Anyway, it's also about time for me to upgrade my own desktop, and I'm looking at AMD64 CPUs for it.

 Scared0o0Rabbit Jan 27, 2005
maybe, but I have a couple games that peg out single cpu systems, when I run them on a dual cpu system instead of 100% cpu use, I get 50% cpu use, with both cpu's sitting at 50% instead of 1 cpu sitting at 100%. Would also explain why windows lets you set cpu affinity for all programs, not just SMP aware programs.

 Alexvrb Feb 8, 2005
Xeons are just not worth it unless you really, REALLY need them. Even Opterons are expensive, although you'll get more for your money (especially in a 4 or 8-way).

 slinga Feb 8, 2005
What really killed it for me is the cost of the ram. PC800 rdimm is expensive shit.

 Alexvrb Feb 8, 2005
RDRAM? Most Xeon boards just use ECC DDR. You can get an older board with 400Mhz FSB that uses PC 2100 for like $130, or something a little newer that uses PC2700 and has a faster FSB. I don't recall if they have Xeon boards with official support for ECC DDR clocked at 200Mhz (DDR 400, PC 3200, whatever you want to call it). But the memory is still more expensive that non-ECC unregistered memory, and the CPUs themselves are very expensive.

As I said, Opterons are a bit better value, but still not worth it unless you really need serious computing power for something. You do a lot of CAD?

On the plus side, the dual-core AMD chips are supposed to hit the market at the same TDP as existing chips. Whereas Intel currently plans to put out something approaching a nuclear reactor in thermal output. I hope for their sake they put some 64-bit extensions in the Dothan successor, and continue on their course to bring it to the desktop en masse.