[outsourced]

Does anyone know how much of the OS has been optimized to take advantage of dual processors?

I'm trying to determine how much more effective the second processor is with common OS functions like memory, video, and hard disk access.

[larkost]

Very much so... there are huge benefits for applications that can take advantage of it, and decent benefits for even those that can't in many circumstances... but the question seems to indicate that you don't know much about how multi threading works:

Most of your disk access comes from one device, and that is ATA... that only allows for one thread in the I/O section anyways... so (non-network) I/O is largely one thread at a time everywhere but in high-end os's like Solaris (where it has the hardware to back this up).

Memory is way to complicated a process to really talk about.

Video... once again... for the actual UI updates this is just like disk access... really, really hard to get right, so eveyone does it in a single thread. But it is also very complicated, so some portions of it can be considered multithreaded... and there is now a lot of involvement of the GPU.... once again much more complicated than this conversation is going to go.

[Detrius]

Originally Posted by outsourced

Does anyone know how much of the OS has been optimized to take advantage of dual processors?

I'm trying to determine how much more effective the second processor is with common OS functions like memory, video, and hard disk access.

I wouldn't expect it to make a lick of difference for any of the stuff you mentioned. Multiple processors will not make your hard drive spin faster, it won't give you a faster GPU, and it doesn't give you multiple memory busses.

However, in general, dual processors will speed up the processing of multiple applications, regardless of whether they are written to take advantage of it. When you have multiple threads running, multiple processors helps. Period. In no way will multiple processors slow you down.

[Big Mac]

MacSpeedZone Power Mac - benchmark page hasn't been updated for awhile, but you'll get an idea of the performance increase of the second processor.