Both Ted Tso on Kernel Planet and LWN refer to an interview to Knuth, TeX author, in which he seems to criticise the choice of multi-core processors.
One quote which I find very short-sighted is:
Let me put it this way: During the past 50 years, I’ve written well over a thousand programs, many of which have substantial size. I can’t think of even five of those programs that would have been enhanced noticeably by parallelism or multithreading. Surely, for example, multiple processors are no help to TeX….
While I agree that it doesn’t help TeX, parallelism is implicit in almost all modern desktop uses (and for what concern servers, I think there is little doubt about its usefulness). Find me a modern desktop when someone is running just one thread that requires CPU time.
Most people (that I know of at least) tend to use their desktop for multiple tasks: reading mail, surfing the web, listening to music, watching videos. Some of these tasks are inherently well-suited for multithreading, but there is one other thing to consider: you usually do all these things at once.
Well, maybe not exactly as once, although it is true for multimedia as you rarely do that exclusively, but you leave mail loading while you surf. And you often leave multiple pages loading at once while you surf, thanks to tabbed browsing. Even when you’re writing something with (La)TeX, you usually have at least the editor and the TeX environment running at once.
Then start to consider other things. You’re connected to the network, almost always in some cases, you’ve got disks that need to be synced properly, you have processes running in background, keeping things in cache, working for you without you seeing them. And you’ve got a mouse that you use, which needs to move a cursor. And wonder what? Xorg is trying to make that take its own thread.
All these things leads me to one conclusion: even if your main applications are not designed to work in parallel, most of the time adding cores will make things running more smoothly. And I’m sure that in the future we’ll see more multithreaded applications anyway, as multithreading, while not suitable for text processing (by design), works pretty well for a lot of other fields.
Myself, I’m waiting for the new Ruby with actual multithreading to port my ruby-elf tools: most of that kind of processing can work in parallel. I’d just need a decent new box. I’m looking for an EU supplier carrying Opterons, but it seems to be difficult to find them, as a person rather than a company.