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grant-skywalker 02-03-2006 08:38 AM

Xeon - HyperThreading - Dual Processor becoming Quad
Hi all,

Recently i'm maintaining a HP ML570 G2 server with dual Xeon 3.0Ghz processor, 4GB RAM, raid 1+0 and raid 5.

Alright, when the server boot up, it shows 4 processors on Xeon 3.0Ghz. I did a preventive maintenance for my client without checking on the real hardware spec. Cuz i'm running some script to gather the hardware informations which i trusted my (eg cat /proc/cpuinfo) thingy on.

It turns out i was fool by the system bootup message. It's actually Dual Xeon 3.0Ghz but my report shows Quad Xeon which i kept arguing with my client.

It's embarrasing but is there anyway, the RHEL ES3 server won't "fool" by the HT thing Intel did to their highend processor??

Is that HT (is it equivalent to Dual Core) really giving double (2 becomes 4 processors) power??


msound 02-03-2006 11:01 AM

All hypertheading does is make 1 physical processor seem like 2 logical processors. Every OS with HT support views a HT enabled intel chip as two cpus. There's no way around that in the OS as far as i know. Some mobos let you disable HT support in the BIOS, though I have no idea why you would want to do it.

Dual core and HT really only help in multitasking and with multithreaded applications. The two technologies are ideal for servers because servers are almost constantly multitasking. Intel dual core cpus are generally faster than single core CPUs with HT. And AMD dual core cpus generally own the heck out of the intel chips.

Brian Knoblauch 02-07-2006 01:10 PM

HT increases performance about 10-30% in my world. So, it's nice, but not a true doubling (execution threads share processor resources).

As far as Intel vs. AMD, it depends on the app, price range, etc. While we've been bringing in all AMD systems for our replacements, I ended up buying an Intel for one user. The Intel dual core w/HT setup came in cheaper AND faster in the applicable benchmarks than the AMD dual core. Comes down to doing all the research specific to your needs before buying.

Darin 02-07-2006 05:10 PM

Just an FYI, another popular OS is also "fool by the HT thing Intel did" and will show four CPUs on a Dual HT Xeon system when you bring up the Performance Tab in Task Manager. :D

grant-skywalker 02-08-2006 01:01 AM


I knew that OS also being "fool" by Intel... but i expect Linux to be "smarter" in a sense to give us a real hardware spec rather than following the "trend".

Besides, is there anyway to check what is the "real" hardware instead of showing Quad Processor instead, it's only Dual?


Brian Knoblauch 02-08-2006 07:58 AM

Well, it's not that easy... It may be wrong, but it's also right. An HT processor has 2 sets of "processor state", so it really should appear as 2 processors. It just so happens that they share execution units, etc... Compare with Sun's new chip. 8 integer cores, 4 states per core, 1 FPU... 32 states can be maintained/run. 8 at the same time, but due to the wait states inherent on each task (for I/O/whatever), it rotates in the next in that group. Acts very close to 32 processors, but if you count integer cores, it's an 8 processor. Count FPU's or chips and it's just a single processor machine!

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