At 11:30 AM -0700 9/9/2009, John Niven wrote: >I find this thread rather surprising. If you research the web, this >used to be a popular Mac question: should I buy the dual or the >single? [snip] >and it maxed out BOTH cpu bars. So I rather fancy that I'd prefer a >slower dual than a faster single. > >Or is "Activity Monitor" lying to me?
The job scheduler is fairly smart. And few Mac users run only one app (process) at a time. Under OS X, processes are put on a processor until they hit their quanta (use up their time slice) or otherwise release it (become blocked waiting for some resource - like a page fault or other i/o). And since multiple processes can be "computable" at the same time, the scheduler can keep all the processors busy. Processes (and the threads they own) do not fly off to the other processors on their own unless the app permits and supports it. This is done because many developers don't take into account the problems of threads completing out of sequence (fooling with causality has consequences)... Grand Central Dispatch, the new job/process/thread scheduler in Snow Leopard, addresses this by creating managed "queues"... so processes (apps) can very easily control how things are done and in what order. The idea is to eliminate the hassle of being multi-processor aware, hoping that more developers will now jump on the bandwagon. Now, while all the above takes into account life from the point of view of the process and thread aspect, you also need to be aware that some frameworks (shared libraries) are multi-processor aware. So even tho the parent process doesn't realize it, they can spit thing off for the scheduler to run elsewhere, kindof like a spider on roller skates... 'Tis a tangled web. - Dan. -- - Psychoceramic Emeritus; South Jersey, USA, Earth. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to g3-5-list@googlegroups.com For more options, visit this group at http://groups.google.com/group/g3-5-list -~----------~----~----~----~------~----~------~--~---
