Microsoft Operating Systems:
 
        Windows NT:
        3.1 Through 4.0 Workstation supports up to two processors.
        3.1 Through 4.0 Server supports up to four processors.
        4.0 Server Enterprise Edition supports up to eight processors.
 
        Windows 2000:
        Professional supports up to two processors.
        Server supports up to four processors.
        Advanced Server supports up to eight processors.
        Data Center supports up to 32 processors.
 
        Windows XP:
        Home supports only one processor. (Not verified.)
        Professional supports up to two processors.
 
    Linux, BSD, and other Unixes:
 
Linux:
 
    All current distributions (2.4x Kernel) of Linux support SMP in excess of 32 processors. 2.2x supports up to 16 processors.
 
BSD:
 
    BSD currently supports up to four processors. However, there is a serious development effort to improve SMP support under FreeBSD. These changes should be out in November of 2001. At this time, I am unaware as to whether the maximum number of processors will be increased.
 
Solaris:
 
    Solaris 8.0 supports up to 128 processors.
 
    Unix:
    There are too many flavors and variables to answer this accurately. Suffice it to say that virtually every Unix supports SMP.
 
    Other Operating Systems:
 
BeOS:
BeOS 5.0 supports up to eight processors.
 
OS/2:
OS/2 Warp 4.0 supports up to 64 processors.