Christian Froeschlin <chr### [at] chrfrde> wrote:
> Fredrik Eriksson wrote:

> > Windows clusters processors into groups of no more than 64 in each group 
> > for performance reasons.

> there are also some restrictions in the classic api such as the
> integer bitmask for thread affinities which only has so many bits.
> On a 32-bit system the limit is 32 logical cores. Probably a case
> of "32 cores ought to be enough for everybody" ;)

  My wild guess is that since the kernel of Windows NT had huge problems
dealing with even 16 CPUs, and since the kernel of Windows XP and newer
are based on NT, they have developed the multiprocessor routines a bit
further, but are probably still hitting some efficiency limits somewhere
at 64 CPUs.

  It's not like it's impossible to write a multitasking operating system
which can efficiently scale up even to thousands of CPUs. Many Unix
operating systems which were built from the very beginning to handle
multiple CPUs are very efficient at it. (If I'm not mistaken, Sun Solaris
is one example. I have heard that it can easily handle 2048 CPUs and even
more, without any significant overhead.)

-- 
                                                          - Warp

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