Is Moore's law the death of Linux?
Interestingly (and quite coincidentally) enough, it's possible that this performance wall will effect *nix applications more than it will affect Windows applications (and it will especially effect *nix derivatives that don't have a preemptive kernel and fully asynchronous I/O like current versions of Linux do). Since threading has been built into Windows from day one, most of the high concurrency application space is already multithreaded. I'm not sure that that's the case for *nix server applications - for example, applications like the UW IMAP daemon (and other daemons that run under inetd) may have quite a bit of difficulty being ported to a multithreaded environment, since they were designed to be single threaded (other IMAP daemons (like Cyrus) don't have this limitation, btw). Please note that platforms like Apache don't have this restriction since (as far as I know), Apache fully supports threads.
Mark Russinovich wrote a great comparison of NT/Linux on multi processor systems in 1999 that explains the multi threading problems that Larry mentions in his post. The latest version of Linux has better threading support but in the last tests results I have seen at work we have better performance with Sun JVM on Win2k3 than we have on Linux on identical hardware.