Last updated December 31, 1996

 Differences Between Windows NT Workstation and Windows NT Server

          Introduction    The purpose of this page is to serve as an
                          accompaniment to the article, "Inside the
                          Difference Between Windows NT Workstation and
                          Windows NT Server" (Windows NT Magazine, November
                          1996). For that reason, a detailed description of
                          the differences between the two flavors of NT
                          will not be provided. Rather, we will present a
                          very brief synopsis of the differences, and we
                          make available the pseudocode that was generated
                          during the investigation of those differences.
                          The pseudocode is commented C-style code, and is
                          best understood by those with some background in
                          NT device drivers.

            Overview of   This list presents an abbreviated summary of the
           Differences    tuning differences in NTOSKRNL, the core Windows
                          NT operating system component.

                             * Telling the difference NTOSKRNL queries two
                               Registry keys during initialization,
                               performs some consistency checking on them,
                               and then sets global variables that identify
                               the operating system to itself, as well as
                               to device drivers, as being Server or
                               Workstation. The keys are originally created
                               and initialized by Windows NT Setup.
                             * System Size An operating system variable
                               called MmSystemSize is used as a factor in
                               several subsystems when they determine how
                               much memory to allocate for various tasks.
                               The threshold for a large workstation is any
                               system with more than 32MB, whereas the
                               threshold for a large server requires more
                               than 64MB.
                             * Worker Threads A server creates twice as
                               many critical work threads on medium and
                               large sized servers than on corresponding
                               workstations. In addition, worker threads on
                               a Server sleep with their stacks locked into
                               memory, whereas on workstation their stacks
                               are eligible for paging to disk.
                             * Memory Management On Workstation the Memory
                               Manager writes dirty data out to disk more
                               readily than on Server. Also, on
                               Workstations with less than 32MB of memory,
                               the Memory Manager aggressively trims the
                               memory footprints of active processes.
                             * Process Management Process quanta of threads
                               on a Server are generally 2-6 times larger
                               than on Workstations. Workstation threads
                               that wake-up after sleeping on an event also
                               get priority boost not obtained on Server.
                             * Memory Stashes On large Servers, the amount
                               of private memory various components (Object
                               Manager, Cache Manager, etc.) allocate for
                               their own use is typically twice as large as
                               on large Workstations.

      Where is NTTune?    We're sorry to disappoint those that were hoping
                          to come to this site to pick up NTTune for their
                          own investigation (NTTune is a utility written by
                          Mark Russinovich that can switch a workstation to
                          run as a server and vice versa), but it is only
                          being made available to members of the press. We
                          do not want to encourage people to violate their
                          Microsoft licensing agreements.

                          Those of you that have been following this story
                          will find it interesting to know that Microsoft
                          altered the code in Service Pack 1's NTOSKRNL.EXE
                          that determines whether NT should configure
                          itself as Server or Workstation, specifically to
                          break the original version of NTTune. NTTune
                          V2.0, which worked on Service Pack 1 and all
                          prior releases, was intentionally broken with the
                          release of Service Pack 2. NTTune has been
                          updated to V3.0, and works on all currently
                          released versions of NT.

      More Information    The following are sources of information on the
                          differences. This page is an addendum to these
                          articles.

                             * "NT Workstation Vs. NT Serverion,"
                               Microsoft's description of the differences.
                             * "Inside the Difference Between Windows NT
                               Workstation and Windows NT Server," Windows
                               NT Magazine, November 1996. This article
                               provides an in-depth discussion of the
                               tuning differences between Server and
                               Workstation.
                             * "Inside the Difference Between Windows NT
                               Workstation and Windows NT Server," The NT
                               Insider Newsletter, OSR Open Systems
                               Resources. This article focuses on operating
                               system differences (NTOSKRNL.EXE), and is
                               aimed at those with some familiarity with
                               Windows NT device driver development.

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                              Pseudocode (27KB)