Bye Bye Baby said:
With all these new technologies with 4, 8 and eventually 24-core capacities (some time in the not too distant future) all running at 64-bit, we musn't forget that software also has tobe developed for these machienes in order to get the most out of the hardware. At the moment we aren't even maximising core-duo, let alone a quad core and all the rest!!!!
It really depends on your application.
On the desktop, if you're a typical user that's just interested in web surfing, playing music files, organizing your photo collection, etc., more than two cores will probably not be too useful. For these kinds of users, even two cores may be overkill, but two are useful for keeping a responsive UI when an application starts hogging all the CPU time.
If you start using higher-power applications (like video work - iMovie/iDVD, for instance) then more cores will speed up that kind of work (assuming the app is properly multithreaded, of course.) 4-core systems will definitely benefit this kind of user.
With current applications, however, I don't think more than 4 cores will be useful. The kind of work that will make 8 cores useful is the kinds that requires expensive professional software - which most people don't use.
If you get away from the desktop and look to the server market, however, the picture changes. A web server may only be running one copy of Apache, but it may create a thread for every simultaneous connection. If you have 8 cores, then you can handle 8 times as many connections as a 1-core system can (assuming sufficient memory and I/O bandwidth, of course.) Ditto for database, transaction, and all kinds of other servers. More cores means more simultaneous connections without performance degradation.
Cluster computing has similar benefits. With 8 cores in each processor, it is almost as good as having 8 times as many computers in the cluster, and a lot less expensive. This concept will scale up as the number of cores increases, assuming motherbaords can be designed with enough memory and FSB bandwidth to keep them all busy.
I think we might see a single quad-core chip in consumer systems, like the iMac. I think it is likely that we'll see them in Pro systems, like the Mac Pro (including a high-end model with two quad-core chips.)
I think processors with more than 4 cores will never be seen outside of servers - Xserves and maybe some configurations of Mac Pro. Mostly because that's where there is a need for this kind of power.