Northwood Xeon(s) with XP Pro - New Information!

[ScottMac]

I have a new system, SuperMicro PC4DCE+ Mobo with (currently) one (Northwood) Xeon 2gig. With "Hyperthreading" (SMT) on, it appears as two processors. If I turn off Hyperthreading/SMT off, it appears as a single processor. I will be adding a second proc soon, but I believe that XP Pro is limited to two processor appearances.

If I leave Hyperthreading off, so that it only sees two (physical) processors, how much of a performance hit an I gonna take on having the SMT shut down? Is it possible/likely that XP Pro can identify the two physical processors from the four processor appearances if I leave SMT on?

I'm thinking I'm probably better off running WIN2K server (up to 4 processor appearances). Comments? Suggentions? (not interested in an AMD system at this point).

Also...some possibly helpful (but slightly OT) discoveries:

Xeon Mobos need a special power supply; It has to have TWO additional connectors, the usual 4-conductor auxillary connector ("P4 Style"), and an additional connector of the same form factor, but with 6 or eight conductors. The usual is for the 4 conductor, and a flat (Molex?) 6-pin. I believe this is an "SSI" spec supply (I got one from Motherboard Express).

Antec cases (at least the 8xx and 10xx) require removing the 3.5" drive cage and full-size PCI card supports to fit the SuperMicro Xeon Mobo. The #1 processor sits right in the middle of where the removable drive cage is located (the floor of the cage support has to be ripped out (it's riveted in).

Other than that, it really whups right along in Seti and Premier. With "Half of a processor" (SMT ON) it does a Seti unit faster than my dual 1 gig P3 (~4 hours). Premier does a 30 minute DV-to-VCD Mpeg1 render in just under an hour (Digigami 1.54 plug-in for AP).

TIA for any insight offered.

Scott

EDIT- News Flash! (well, maybe not)...a current article over on 2cpu.com indicates that WIN XP DOES recognize physical CPU vs. logical/SMT/Hyerthreaded processor appearances. As such, it will allow two Northwood Xeons, each with SMT enabled...and it (alledgedly) has code to take advantage of SMT (or at least more so than WIN2K). I'm gonna load it on a spare drive and try it out. My second processor arrives Wednesday...I'll post something probably thursday.

 

[mastertech01]

I wonder if it would be possible to use 64bit XP using hyperthreading? I know that sounds strange but so does seeing two processors when only one is present. How does the system monitor report CPU usage in that environment? Does it monitor two processors as it would if two processors are present?

 

[ScottMac]

Yep, it does. If you didn't know there was only one processor, nothing in the Windows displays would tip you off. The system Manager loaded the ACPI Multiprocessor HAL code, the Task Manager "Performance" display shows two windows, etc.

Performance-wise, the Task Manager displays are virtually identical to the Dual 1gig PIII machine I have (as far as processor usage, affinity, etc): the OS believes it's looking at two processors.

I don't think the 64 bit version would run, I believe it has different binaries (like for a Tandom , Alpha, or Itanium).

I can shut down the Hyperthreading, that's not the issue (if there even is an issue), I'm just wondering how much of the processor I'd be throwing away by killing the SMT features.

I'm liking the Xeon alot, but it's hard to believe I'm the first guy with this "problem."

I did some searching on the MS knowledgebase and support areas, and Intel's as well, but so far, nothing really addresses the issue. I'm pretty sure it falls into the "Well, dummy, if you want to run (what looks like) more than two processors, you need WIN2K Server, or *nix" (I am kinda curious how this would do with Linux...since there's not much loaded, I might scratch it and give it a try).

I can't leave it as a Linux box though, I built it to be a decent Video box, I already have (and like) Premier.

Thanks for the response though. If you have any other questions...fire away.

Scott

 

[AndyHui]

Having 2 additional power connectors is not exclusive to XEON motherboards. Many of the older P4 motherboards, and some of the new ones, such as the ASUS P4T-E, have both connectors: the 2x2 molex and a plug that looks like half of the old AT power supply.

You are correct in that WinXP Pro can only cope with 2 processors. Switching SMT on with 2 processors does make it effectively 4 processors to WinXP, so to take advantage of it, you need Win2K Server.

SMT gains can be quite significant depending on the application. I have seen it stated that you can gain anywhere between 30% and 50% performance, possibly more once programs are optimised for it.

 

[ScottMac]

Thanks Andy (Nice job on the FAQs, BTW).

Yeap, I know about the motherboards that use both; I have another Supermicro motherboard that uses two additional connectors (the 2X2 Molex, that the flat / half AT power connector-looking-connector).

The Xeon board (at least the SuperMicro) has the 2x2 Molex, then (instead of the flat/half-AT-power-looking connector) is another Molex connector (2x3 or 2x4). Two connectors, both Molex-style...that's what got me.

I bought a 500 watt ATX 2.03 ATX12V (blah blah blah) commonly available (I got this one at CompUSA)....and it had the flat/half-AT-power-looking connector...but the new MB doesn't use that style...it needed the SECOND Molex-style connector (a 2x3 or 4 in addition to the usual 2x2).

That's what I was trying to point out....if you get a Xeon motherboard, you gotta watch which power supply you get for it. ATX 2.03 isn't good enough, ATX12V version 1.1 isn't good enough. I believe it has to be "Server Specification Infrastructure" - SSI (information at www.ssiforum.org).

SSI might also specify current-per-voltage-rail. I dunno, this is the first I've seen/heard of it....but I don't do many "Server" class boxes these days.

Thanks for the info. I'm pretty sure at this point that Win2K Server is in my future for this box.

Take care

Scott

 

[PeeluckyDuckee]

The regular P4 is 478pins and the Xeon P4 is 603pins, correct? Mind if I ask how much did you pay for the CPU and the mobo? What's the default voltage on the P4/P4 Xeons? Thx.

Plucky

 

[ScottMac]

Xeons are 603 pin. The monitor says 1.49 volts. Temp is 94 F. with Seti and 3DMark2001SE running (standard HSF).

I got the motherboard a SuperMicro P4DCE+ and processor (2gig) for ~US$1300.

The 460 watt power supply was ~US$120.00.

FWIW

Scott

 

[mastertech01]

When I was considering The Xeon P4 I was looking at the P4DC6 I believe it was, and it required the use of the Super Micro PWS-024 power supply, which had the connectors you describe. It was like 155.00 at most places you could find it, but was scarce back then. THe mobo was 600.00 and the 1.7 processors were around 500 each.. Then Anand thrashed that idea with his review that showed the dually MP Athlon was better. So I abandoned the idea for the time.

That was the original P4 Xeon processor.

 

[ScottMac]

Bump, one time, for the new information.

Scott