> The Thread Manager is an operating system enhancement which allows
> applications, which have been written to take advantage of the
> Thread Manager, to perform multithreading. Multithreading allows an
> application process to be broken into simple subprocesses that
> proceed concurrently in the same overall application context.
>
> Typically, the Thread Manager extension is shipped with, and
> automatically installed by, applications that support it.
>
> ? Excerpt: from the included documentation.

DL #1: Thread Manager 2.1 ?Contained inside of the StuffIt 3.6 "sit"
archive is an 800k Disk Copy 4.2 floppy disk image. Use Disk Copy 6.x
to mount it, or add it to an emulator's drive list, etc.

 * Notes:
   * This software is built into and included in with the Mac OS from 7.5 onward. This extension not required from that System release onward. It is only required by applications that need it, if running Macintosh System Software 7.0 to 7.1.2

   * This extension may also be included with and installed by Apple software of the period, such as Drag Manager, QuickTime 4, etc; when installing to Mac OSs earlier than System 7.5

Some but not all software distributions that support it, shipped with
this Extension. This is archived here for those occasions where it may
be needed. - Most early internet savvy programs require its presence.

Programs requiring this software (but not including it in with their
distribution):
[ResCompare][1]
[iCab 2.9.9][2]

Compatibility
Architecture: 68k PPC

This System Extension is a FAT binary and runs native on 68k & PPC
Macintosh.

  [1]: http://macintoshgarden.org/apps/rescompare-v26
  [2]: http://macintoshgarden.org/apps/icab