Why Faster CPUs? What About SMP?

Codeine asks: "As we press harder and harder against the physical limitations of speed, why do CPU manufacturers continue with the costly faster single processor model, instead of focussing on multi-processor designs? The new IBM Blue Gene seems to be acknowleging that more/simpler processors is the way to go (very like non-AI, millions of neurons). Why aren't we seeing commoditisation of SMP?"

Comments

Apple and Microsoft

[Matthew Weigel]

First of all, to some extent SMP is being commoditized -- Apple, for instance, is now selling SMP as being a simple one-step upgrade from UP in their PowerMac G4s. Apple is also the computer vendor that brought us widespread use of USB, the focus on industrial design as a consideration buying computers, etc. Expect other vendors to follow that lead, insofar as they can load operating systems that can take advantage of SMP.

Microsoft should probably credited with holding systems back to single processors with Win9x/ME, and yes even WinNT. With NT, IIRC, processes, not threads, were spread across processors -- so you saw very little benefit running a single, multi-threaded app on an SMP system. I would hope W2K does something more reasonable, as in something that virtually every other SMP implementation does (notably, except MacOS pre-X), and spread threads across processors.

Finally, in the x86 arena, only intel can support SMP currently -- and considering that AMD has been providing a much better price/performance ratio for some time, and is even generally ahead in performance right now. That makes it more difficult to justify going with lower-performing, more expensive processors to increase performance, although of course the difference between dual 800MHz P3's and a single 1.1GHz Athlon should be quite noticable if you're running a well-threaded application (or lots and lots of processes).

All that is for PC systems (including Macs as Personal Computers, if not Wintel PeeCees :). For other architectures (alpha, sparc/ultrasparc, MIPS, PA-RISC for instance), SMP is alive and well. SGI's highest-end workstations-that-could-be-servers, Octanes and Octane2s, support two processors, and their servers support a lot of processors. Sun has SMP workstations and ridiculously SMP servers as well; I've seen a lot of SMP alpha motherboards, but since alpha's are almost as commodity as PCs I haven't checked out what sorts of systems [c|o|m|p|a|q] sells. Hewlett-Packard also sells SMP workstations and servers, but my experience with them is with the old HP 9000/7xx series that are largely, if not completely, uniprocessor.