Two Xeon 2.8 MHz vs. one 3.06 but with 1MB L2 cash

[supplier]

Hey all,

please give me your opinions witch way is to go in upgrading my dual CPU capable dell precision 650 workstation. For around $750 i can install two 2.8MHz Xeon CPUs 512kB L2 cash each or one 3.06MHz with 1MB L2 cash and put it in HT mode (all working on 533MHz FBS). Any ideas what would be better/faster for video rendering/processing?

i'm guessing with two CPUs it makes no sense to enable HT as XP can't handle 4 CPUs efficently.

thanks all.

[MaXiMuS]

for divx encoding this math aplies almost exactly

2x2.8 GHz = 1x 5.6 GHz

so in my opinion dual 2.8 setup should be much faster than single 3.06 no matter the size of cache...

( = interchange with almost )

[supplier]

Guys, i didn't make myself clear. these xeons can work in Hyper-Threading mode (as two virtual CPUs). IMHO 3.06MHz in HT mode makes two virtual 3.06MHz giving total 2 x 3.06 = 6.12MHz with 1MB cash, and two real 2.8 MHz give 5.6MHz with 2 x 512 kB = 1MB cash. But still two real CPUs at 2.8 GHz might be faster than two virtual at 3.06MHz On other hand cash sizes are equal. Also 2.8 cost $340 each and 3.06 cost $760 So....should i go for $80 savings and two real CPUs or not? what would you do?

[Iznobad]

Two Real CPU's are more efficient than a singly with hyperthreading. Hyperthreading only takes advantage og some unused processor ressources. So you cannot just double the HT processors speed.

A rule of thumb would be:
20-30% more for a HT processor
60-70 for the real CPU's

/Iznobad

[MaXiMuS]

Originally posted by Iznobad
Two Real CPU's are more efficient than a singly with hyperthreading. Hyperthreading only takes advantage og some unused processor ressources. So you cannot just double the HT processors speed.

A rule of thumb would be:
20-30% more for a HT processor
60-70 for the real CPU's

/Iznobad


;) i agree

[ppera2]

Originally posted by supplier
Guys, i didn't make myself clear. these xeons can work in Hyper-Threading mode (as two virtual CPUs). IMHO 3.06MHz in HT mode makes two virtual 3.06MHz giving total 2 x 3.06 = 6.12MHz with 1MB cash, ...

Where did you get this (nonsense)? Hyperthread is in fact only task switching moved from software to hardware (CPU). All speed gain comes from that. And in real world gain is not so much, usually under 10%.

[geoffwa]

While Hyperthreading gives a neat performance increase, it's not the equilvalent of two processors.

Be aware that XP Professional supports up to 2 CPUs (or 1 HT CPU in this instance) and you'll need to use 2000/2003 Server if you want proper support. Don't turn off Hyperthreading!

[Sirber]

Linux kernel 2.6.0 supports up to 256 processor IIRC... :D

[supplier]

Guys i'm confused with geoffwa's answer. With XP pro and two real CPUs should i set HT in BIOS on or OFF. (i ordered two cpus and i'm not upgrading to the windows servers.

Thanks

[Sirber]

Try with. IIRC Windows 2000 WS supports up to 4 processor.

[Ramirez]

supplier: both, HT/SMP fits into exiting Win-XP HAL model () or in other words the O.S is capable of distinguish between one HT/ and 2 physical SMP processors.

Your pair of Xeon CPUs will be identified as 4 logical processors and it'll work correctly under XP Pro, there is no need to turn the HT OFF.

[Sirber]

God Ramirez has spoken! :D. I'll have to swirch to P4 on my next upgrade then :)