Quad-core - what is it good for?

April 9, 2007 4:43 PM

I'm thinking of buying a quad-core PC and want to check that my understanding of what a quad-core PC could do for me is correct.

In simple terms, my understanding of a quad-core PC is that it's effectively 4 CPUs on the one chip. Now I understand that quad-core does not equal to 4x performance because many/most applications are not (currently) designed to utilise multiple cores.

However, my main reason for thinking of getting a quad core is so I can do the following scenario: One core for 'normal' stuff like surfing the Net, using Office, playing World of Warcraft :). Another core to permanently run VMWare or other virtualisation software running Linux. The remaining two cores to be ripping a DVD to divx or perhaps using Adobe Premiere to encode a video etc.

In the above scenario is it (a) possible to allocate applications to specific cores? (b) would I be able to do what I described with no performance impact (eg the CPU intensive DVD rip won't slow down my VMware session or WoW since it's on a separate core?)

Thanks.

posted by tobtoh to Computers & Internet (6 answers total)

You can certainly allocate applications to specific cores: it's called processor affinity. But you generally don't need to do that. The operating system should be smart enough to allocate tasks among the processing cores automatically so you can rip DVDs and encode video while playing WoW. Setting VMWare to run on one core may be a good idea, but you certainly don't have to do it.
posted by marionnette en chaussette at 5:31 PM on April 9, 2007

What you are looking to do is 'set processor affinity'.

There are times this helps and times it doesn't, ultimately you will have to play around with whether or not it is worth if for each application.

Here are some links:
http://forumz.tomshardware.com/hardware/set-processor-affinity-automatically-ftopict179198.html

http://www.xtremepccentral.com/forums/archive/index.php/t-1191.html
posted by jkaczor at 5:33 PM on April 9, 2007

I should think that quad cores will help you with your multiple processes. I don't think, however, that you'll need to explicitly schedule your apps. OS's are generally pretty good at this.

One thing to keep in mind is how many of your applications are disk bound, and what the configuration of your disks is. For example, divx encoding and Premiere are going to eat up i/o bandwidth. If WoW and the VM are running from the same hard drive (or in the case of IDE/PATA, the same controller) then you're system will feel slow no matter how many cores you have.
posted by sbutler at 5:44 PM on April 9, 2007

Response by poster: Thanks for the answers everyone - looks like I can happily go off an buy a new PC now :)

And you raise a good point sbutler about the non-CPU constraints - i'll keep that in mind when I work out the specs.
posted by tobtoh at 6:05 PM on April 9, 2007

The amount of RAM you have will almost certainly matter much more than the number of cores. I'd take a dual core 4GB system over a quad core 2GB system any day of the week.

Note that if you go for more than 2GB RAM you should highly consider running a 64 bit version of the operating system. Especially with 4GB RAM installed, you will only get about 3.5 usable gigabytes due to address space limitations.
posted by Rhomboid at 6:39 PM on April 9, 2007 [1 favorite]

Like Rhomboid, I might favor a dual-core machine with a fancier video card and more RAM; in most systems, the CPU isn't the bottleneck, RAM (and if gaming, video) is- if you are going to go quad-core, get the fastest system bus you can, otherwise, the cpus will likely be starved with your workload. Also, adequate cooling may be more of an issue for you; my dual-core box heats up the room pretty good.
posted by jenkinsEar at 9:22 PM on April 9, 2007