Is a dual core 3ghz processor two 1.5g ghz??

[Rudyard]

Just wondering how a dual core processor works, I have a 3ghz Pentium D and know of the more recent core 2 duos and such but was wondering how they work.

Do they run 2 sets of instructions at 3ghz or at 1.5ghz each to equal 3ghz??

And also where do dual core proccessor bottleneck? I mean if they run 2 sets of instructions in seperate cores but are on a single processor there must be some congestion where the 2 sets have to exit? (I think of 2 car lanes with shorter traffic slowing down to merge to 1 lane as opposed to one long line of traffic that flows)

I have most likely confused the situation completely 8)

[redwudz]

Here's a couple of articles:
http://www.short-media.com/articles/dual_core
http://www.pcstats.com/articleview.cfm?articleID=1797

From the second article:

The processors co-ordinate and share information through the system bus, and the processors arbitrate the workload amongst themselves with the help of the motherboard chipset and the operating system.

It's about the same as having 2 separate CPUs, but with the controllers as part of the CPU chip. If they were 3Ghz CPUs, they would both run at that speed. The 'bottleneck' would likely be the system bus.

Both those articles are a little old, but I found them with a Google search for 'how do dual core cpus work'. There are many more articles, some may be a little newer.

[edDV]

Core2 has other speed ups that make clock GHz comparisons obsolete. Better to use performance benchmarks for your applications of interest.

[Krispy Kritter]

Also keep in mind that not all apps are written to use dual core technology. So don't just assume that getting a new cpu will speed up all of your apps.

[Rudyard]

Actually krispy kritter I was also curious on that....when looking at the task manager whilst encoding Sony Vegas 5 only uses 50%, so Im guessing it is single threaded and I can run another session and encode 2 things at once.

However some programs use 100%, does that mean they are multi threaded as it uses the full CPU?

Also as they market dual core as good for mulitasking if multithreaded applications became normal doesnt that negate the affect of dual core for multitasking because it is programmed to use both cores??

[jagabo]

Actually krispy kritter I was also curious on that....when looking at the task manager whilst encoding Sony Vegas 5 only uses 50%, so Im guessing it is single threaded and I can run another session and encode 2 things at once.

Yes, unless you're disk bound rather than CPU bound. I'm pretty sure Vegas is multithreaded -- check to see if there's an option somewhere.

However some programs use 100%, does that mean they are multi threaded as it uses the full CPU?

Yes.

Also as they market dual core as good for mulitasking if multithreaded applications became normal doesnt that negate the affect of dual core for multitasking because it is programmed to use both cores??

To some extent, yes. I suspect that the number of cores will be increasing faster than programs' ability to use them though. It's usually not too hard to split a program into a few threads. But many programs aren't amenable to massive multithreading.

[redwudz]

The second part of your question about programs that use 100% of both cores. You have the option, 'Set Affinity' for how many cores are used in Task Manager Processes. I do that for some programs so I can continue multitasking with the other core. XP has up to 31 CPUs you can set to be used or not. A 31 core processor; Now that could really do some multitasking.

[jagabo]

You have the option, 'Set Affinity' for how many cores are used in Task Manager Processes. I do that for some programs so I can continue multitasking with the other core.

I usually just set the process to low or idle priority. That way it has little impact on the system but doesn't take much longer to finish (as long as the other stuff I'm running isn't too CPU intensive).

[BJ_M]

Actually krispy kritter I was also curious on that....when looking at the task manager whilst encoding Sony Vegas 5 only uses 50%, so Im guessing it is single threaded and I can run another session and encode 2 things at once.

However some programs use 100%, does that mean they are multi threaded as it uses the full CPU?

Also as they market dual core as good for multitasking if multi threaded applications became normal doesnt that negate the affect of dual core for multitasking because it is programmed to use both cores??

vegas 5 is multi threaded for only some processes .. vegas 7 is fully multi threaded - but some filters/rendering are not by necessity ..

you can also work on one cpu and render on the other at the same time using network rendering on the same machine -- which is kinda neat ...

[edDV]

you can also work on one cpu and render on the other at the same time using network rendering on the same machine -- which is kinda neat ...

You can even use two encoders at once without it bogging down the user interface.

BTW: Intel was showing a demo today at the Embedded Systems Conference that MPeg2 video stream encoding benchmarks scale linearly from Core2 Duo to Core2 Quad. They were showing 4 real time streaming one Mb/s videos on the Duo and 8 on the Quad with similar per channel performance.

Some doubters were concerned shared memory controllers would slow performance.