Dual CPU doesn't boost the performance

[NiklasJ]

I've got a dual-processor system running WinXP Pro SP2. When benchmarking the PC using PassMark's PerformanceTest, the test results lie at approximately half of that of comparable systems (or equal to single-CPU systems).

The BIOS setup program does not display any temperature or voltage values for the second CPU, only for the first. From this, you might draw the conclusion that only one CPU is active. However, the Windows Task manager displays two CPU graphs - one graph per CPU. So Windows (but not BIOS ?) detects both CPUs.

I have updated the BIOS software as well as the chipset drivers. But the performance still equals that of a single-CPU system. Help, anyone?

Thanx!

/ NiklasJ

CPU: 2 x Intel Xeon 2.80 GHz
Chipset: ASUSTeK 82875P
Memory : 2GB DDR-SDRAM
Video adapter: NVIDIA GeForce 6800 LE

 

[edemiere]

Someone correct me if I am wrong, but the software you are using, as well as the operating system have to be coded to make use of a second CPU?

I personally have never fooled with this, but as far as I understand the technology it has to be coded that way. Much like having a 32bit processor with Windows 3.1, it's still 16-bit code and can't take advantage of the 32-bit capability in the CPU unless specifically coded to do so. Or even today's Athlon 64 CPU's. You'd have to have the 64-bit version of Windows XP for it to run and show the real performance gain of 64-bit processing.

I could be wrong, but that's how I understand it.

 

[Sympology]

Edemiere is correct, the app has to support dual proccessor (multithreaded). It's normal high end apps (Audio / Video / Art) such as Adobe Photoshop and Steinberg Cubase.
On top of that bench marks are now thrown by multithreaded single cpu's and multicore single cpu's.
On top of this, even correctly configured multithreaded app will not run at 2x single cpu speeds. It's normally 1.5x at best. Plus you have issues such as video cards, bottle necks, memory etc etc etc.

Stu..

Only the truly stupid believe they know everything.
Stu.. 2004

 

[nlm9802]

task manager might be showing you just one cpu with hyperthreading turned on? I know my p4 3.0 at home shows 2 cpu's in task manager, I only have one cpu though.

 

[cdogg]

Niklas,
As you may have discovered the hard way, a dual-processor system will not enhance performance by 2x. In many applications, only one CPU will be utilized unless the app was written in such a way to "multi-thread" and take advantage of the second CPU.

However even with a non multi-threaded app, Windows XP is intelligent enough to offload some background processes to the 2nd CPU while the other chugs away. This does free up some resources and increase overall performance. The real gain is when you are running many apps at once, or have a lot of windows open.

Even so, don't expect twice the speed! You might see at most a 10% increase when working with regular apps. As Stu pointed out, other apps like Adobe's Photoshop or Premiere, you might see as much as a 50% increase. Only in a server environment would you expect these numbers to be higher.

Just my 2¢


~cdogg
[tab]"All paid jobs absorb and degrade the mind";
[tab][tab]- Aristotle
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[SkipCox]

I have a friend who put a dual xeon machine up against 4 athlon xp rigs hoping the dual xeon would do the same folding work.

It would cover three XP rigs but would not hand with four. It would likely do better or worse depending on the applications.

The responses above must be correct and as they say...your results may vary.

Skip

http://home.comcast.net/~skip9/index.html

http://scc.i8.com

 

[NortonES2]

Never done it with a workstation but when you add another CPU to a server you have to update the HAL.

Also if task manager is reporting 2 CPU's then as mentioned above this is the hyper-threading, if both CPU's were recognised then task manager would show you 4 CPU's

-------------------------------

If it doesn't leak oil it must be empty!!

 

[NiklasJ]

First of all: thank you all for taking the time trying to help me out here, i really appreciate it.

I found a benchmark test carried out on a similar system (dual Xeon 2.80 GHz) using PassMark's PerformanceTest. My system got somewhere between half and 2/3 as many points. Something is definitively wrong.

Based on what both nlm9802 and NortonES2 said about hyperthreading and the Task Manager, and the fact that BIOS doesn't report a second CPU, I have at least come to the conclusion that this is not a Windows issue.

So why won't BIOS detect the second CPU? Both CPUs have been tested ok, so we can rule out that possibility. I found out that the power supply is capable of delivering up to 450 W. Could it be that one CPU is shut down due to lack of adequate power supply?

 

[danomac]

I remember on one of our servers I had to change a jumper on the motherboard to tell it that there was a second processor when I installed it.

Have you looked for something like that?

 

[joemck2004]

The "normal" Windows XP seems to be licensed only to use one CPU. You either have to buy a multiple CPU license from Micro$oft or use Linux instead.

 

[bcastner]

XP Home - 1 CPU
XP Pro - 2 CPUs, which if both are HT would show legally as 4 CPUs

The Microsoft license counts only physical processors, and the dual Xeon setup discussed is perfectly license legal.

A great resource page for dual and HT issues, including licensing questions:

http://www.buildorbuy.org/p4ht.html