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Dual Processors

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Anonymous
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a b V Motherboard
August 22, 2001 2:15:24 AM

I read alot of people writing about dual processors. I want to know more about how it works, anyone know of a good article. I have a few questions:
1. Do dual processors have a symetric setup, meaning both processors have knowledge of the OS and share responsibilty, or is a master/slave relationship - master passes on processes to the second cpu.
2. When you get a motherboard that supports dual cpu's do you have to have both cpu's in at the same time, or can you get one and possible get the other at a later time, do the motherboard support cpu faults -meaning one could die and the system would continue running with just one cpu.
3. Given that you can get the same type processors, say dual 600's compare to a single 1.2ghz. Would one be faster than the other?
4. What is the price difference between dual processor motherboards and a single?
5. Finally, do they have to be the same cpu, because some motherboards support multiple platforms.

More about : dual processors

August 22, 2001 3:16:12 AM

1) An x86 dual-CPU system generally powers up with only one CPU active. The O/S is responsible for activating additional CPUs and deciding which CPU does what. The CPUs generally don't know anything about the O/S. If the O/S doesn't support symmetric multiprocessing (SMP), only the primary CPU will be used (yes, that's a waste).

Some operating systems will manage SMP more efficiently than others. Win95/98/ME and (last I heard) OpenBSD do not support SMP at all. Linux 2.2.x has poor SMP support; WinNT/2K has decent SMP support; Linux 2.4 and FreeBSD 4.x have excellent SMP support.

2) You can run a dual-CPU motherboard with only a single CPU. Some motherboards require (and usually come with) a separate terminator for the secondary CPU slot. Some don't require the terminator, some only require it for certain speeds.

3) A single 1.2GHz is almost always faster than a dual 600MHz, especially with x86 CPUs. The best you can hope for with dual CPUs is for there to be a constant load of two or more threads/processes, and even then, you probably won't get all of 1.2GHZ performance.

4) Generally, for a dual-CPU x86 board that has the same features as a single-CPU board (aside from the second CPU), I would expect to pay 25-50% more. That's just my estimate though.

5) In general, yes. With some setups, it's even important to have identical steppings on the CPUs (the stepping of two CPUs might be different, even if their rated speed is the same).

Kelledin

"/join #hackerz. See the Web. DoS interesting people."
August 22, 2001 3:50:13 AM

Reply to part of #2: If you load an O/S into a machine with a single processor, the kernel is setup for a single processor. When you add the second processor, you have to redo the O/S for two. Something to bear in mind.

Sweating like a rancid chunk of pork
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Anonymous
a b à CPUs
a b V Motherboard
August 22, 2001 4:34:02 AM

you guys know your [-peep-], thanks for the replies, so if I'm running win98SE it will not take advance of the dual processors OR "redo" the OS for two, I mean selecting a certain setting or is it more complicated than clicking a radio button, OR get a OS that supports it, win2000 is this the only option? I'm not upgrading just yet..., but I'm picking through and weighing the options.
August 22, 2001 5:13:04 AM

Generally WinNT/2K will autodetect whether you have multiple CPUs or not during installation. With Linux, it depends on your distro.

With WinNT 4, if you install on a single-CPU box and upgrade to dual-CPUs later, you either have to reload the O/S or use a little utility on the NT CD called "uptomp.exe". WinNT installed for a single-CPU system <b>will not</b> load on a dual-CPU system. Not sure how it is with Win2K, but I seem to remember hearing that it's a bit simpler--a radio button somewhere in Device Manager.

Linux installed for a single-CPU box will still load on a dual-CPU box, but you'll need to update your kernel to take advantage of the second CPU.

Kelledin

"/join #hackerz. See the Web. DoS interesting people."
Anonymous
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a b V Motherboard
August 23, 2001 11:24:42 AM

I got it. thanks. I might consider this option in a few months, I think I can hold out for the price wars make the cpu's dirt cheap, if I'm going to upgrade why not UPGRADE.

I might be ignorant, but I'm not stupid.
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