Single vs Dual Processing.

Adding another processor can be likened to adding another cylinder to a car engine (or similar); without something to send fuel and ignition sparks to the extra cylinder, it will not contribute anything to the engine's performance.

Multiple CPU systems need software or hardware that can send instructions to several processors and collate the results (threading). Some programs (e.g. 3d modelling/rendering software) have built in multi-processor support, but it has to be configured manually for everything else.

Marginal performance gains per CPU are inevitably less than 100% because of hardware reasons, but you should get substantial gains if the threading software/hardware is doing its stuff properly.

It's mostly a workstation (CAD, SFX), server, and supercomputing thing though; gamers wouldn't see much benefit.

"Some mice have two buttons. Macintosh has one. So it's extremely difficult to push the wrong button." - Apple ad. circa 1984.

Usually I find that if you don't know why you need more than one processor, you don't need it. More than one processor on a system requires specialized software to utilize the extra power and the gain is somewhere between 15%-25% for optimized programs. You will normally find that you take a performance hit in programs that are written for a single CPU. Generally programs that are processor heavy (number crunching) are the ones optimized for multi-processor systems. Home users usually do not run serious crunching so unless you do a lot of rendering or have a huge database you will actually decrease performance.

Dev

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It's not like the second processor ONLY gets used when a program is written for it, it is used quite often actually. One program will run one processor and another could run on the 2nd processor. This is good for things that are CPU intensive but aren't written for dual processors; it enables you to multitask when you normally can't. For instance, you can encode a movie with Gordian Knot and also run your computer with the normal tasks all at once. Or, when a system is very well setup, you can run two intensive tasks at once, i.e., you can play a game and encode MP3s in the background for instance. Though very expensive, I think they are worth the money (I do not have one, but I use them every so often), even when you don't run optimized programs.

Damn Rambus.

Erm, actually, no, sorry. Adequately coded scanline rendering gets something like a 95% speed boost from a second processor; some other programs benefit similarly, but they're very, very few...

  <font color=red><b>M</b></font color=red>ephistopheles

Dual processor systems totally kick ass. Most people on here blethering about them have never owned or used one. I have owned, built and used 3 dual processor systems in my time, and they all worked incredibly well under high workload or network usage. But if you just want a machine to play Quake at 600fps on, then they're not for you.

<A HREF="http://www.anandtech.com/myanandtech.html?member=114979" target="_new">My PCs</A> :cool:

Captain Obvious says the number of dedicated multiple CPU programs are very limited in number!

However you can run two programs at once with ease, or one program while the system still feels smooth and fast!


<b><font color=red>Captain Obvious To The Rescue!!!</font color=red></b>

Having 2 cpus is like having 2 cars...you wont be able to drive twice as fast, you will only be able to carry twice the amount of people at the same speed.

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It's not important to know all the answers, as long as you know how to contact someone who does.

Hey, nice comparison there...

Someone I know also said that a server isn't supposed to be a fast car, but rather a big fat bus that can carry much more people from one place to another.

  <font color=red><b>M</b></font color=red>ephistopheles

--Adequately coded scanline rendering gets something like a 95% speed boost from a second processor--

True, the same goes for any radiosity based engine and raytracings.

Generally for most of the population a second processor isn't as useful as a faster single processor. This is especially true in applications which aren't optimized for smp operations. A single processor 2ghz system runs winamp, outlook, 2 copies of star wars galaxies, and a web browser pretty fair. Would two processors run that load better? Yes. However if you're only running a single game at once and the applications isn't smp optimized, you're better off just increasing system speed or having a higher end graphics card.

Shadus

That makes sense and I support that... I've worked with a dual P3 933Mhz before... and I don't know if I'd have done that again, if I had the choice to... I mean, it was terribly expensive...

  <font color=red><b>M</b></font color=red>ephistopheles

I had dual 450s (which now makes a very nice linux box) and I liked them, but I wouldn't invest that kinda money in a mobo now unless I really needed it for something like cad/graphics/etc

Shadus

yes, that's about the same conclusion I came to as well! :smile: I'd rather go with a powerful, balanced single-processor system instead...

  <font color=red><b>M</b></font color=red>ephistopheles

Nod, spot on.

I *do* think however, that within a generation or three that multiprocessor systems will be standard. Be it multiprocessors on single chip or multiple processors in general. Shrug, we'll see.

Shadus

I think so too... and although multiple processors would be quite flexible, I think multicore chips might be the way the guys in control choose... 'cause it might be easier to produce...

  <font color=red><b>M</b></font color=red>ephistopheles

Easier to produce and probally faster communication between chips also.

Shadus

yes, and you wouldn't have to rely all your interprocessor communication on some of the (rather bad) chipset designers out there... Yikes! :smile:

  <font color=red><b>M</b></font color=red>ephistopheles

*cough*via*cough*

Shadus

SOMETIMES HYPER THREADING (HT) HAS PROBLEMS

A new P4 3.06GHz CPU is "multi-threaded" but dual CPU systems are not problem free. My experience is below.

I have a P4 3.06GHz Intel HT CPU that seems to have strange issues with the hyper threading feature.
First, I checked all the normal HT technology indicators were set correctly.
Intel 845 chipset HT enabled ASUS P4PE motherboard has most current BIOS (1006).
Multi -Threading or Hyper-Threading is turned on in BIOS.
Initial boot screen shows both processors as CPU1 and CPU2.
XPSP1 HT aware operating system shows both processors in the Hardware Manager within XP.
So far so good it seems.

The problem is when I try to use the Outlook Express / MSN mail program in XP. If I try to open the program, it doesn’t respond at all. I have to close Express / MSN with the CTR/ALT/DEL end now function and open my IE6 Explorer, and then open MSN mail from the read mail feature. Then it seems to open. I use this program every day, so why won’t it work with this CPU with HT enabled? Going into BIOS and disabling multi-threading fixes the problem. Reboot and Explorer opens fine in any order with no “not responding” issues.

What is broken the CPU, the program(s), the Operating System or the associated hardware and how to tell? Right now I paid a lot of money for a CPU that doesn’t do what it is supposed to do.

Are their any benchmarks that are HT enabled? Is Mad Onion’s 3Dmark 2003 HT aware? Is my second CPU per say working? With “one” CPU enabled the system runs fine. I really can’t explain Outlook Express / MSN’s issues except it hates HT turned on. This old program can’t be HT aware, yet it locks-up with HT enabled. I thought things were to run as though no HT existed with any non-HT aware programs. Not so, it seems. As is, I have to disable HT to use my computer.

Comments? Anybody have issues like this? Could my CPU be broken and how to tell what is if it’s not?