
            ͻ
                     HARD DISK CACHE DEVICE DRIVER          
            ͼ

I. Description :

     The CACHE.SYS is a hard disk cache device driver that
     lets you set a disk cache from 1K to 512K size in extended
     or expanded memory.  The default cache size is 256K.


II. Program info :

      Version       : 1.0
      Release date  : 04/18/1990.
      Resident size : 8KB    (In conventional memory)
      Hardware      : PC-AT or above, with extended memory or expanded
                      memory with an EMS manager.

III. Product files :

       There are two files in the directory -
       (1) CACHE.SYS - Hard disk cache device driver program.
       (2) CACHE.TXT - This documentation.


IV. About CACHE.SYS :

      (1) Command parameters :

            Add a one line command into the CONFIG.SYS file for the
            boot up drive:

            DEVICE=C:\CACHE\CACHE.SYS /xxx

            /xxx : Specify memory size of extended memory use by
                   CACHE.
                   For example :    /64
                   specifies that there should be 64KB of extended memory
                   or expanded memory for CACHE to use.


      (2) How CACHE.SYS works :

          (1) CACHE will check for the existence of VDISK.SYS to
              determine the bottom address of extended memory.
          (2) CACHE will check whether the expanded memory manager
              exists and whether the expanded memory is enough for the
              cache to use. If the expanded memory manager does not exist
              or the expanded memory is not enough for the cache to use,
              CACHE will use extended memory automatically.
          (3) CACHE uses the "top-down" method to allocate extended
              memory. It takes over the BIOS extended memory size system
              call (INT 15h function 88h) and reports less extended
              memory available than is actually present on the machine.
          (4) CACHE.SYS is a direct mapping cache and does not
              read ahead.


      (3) Problems with certain packages :

          (1) You are advised not to run the PC-CACHE.COM file in PCTOOLS
              after installing the CACHE.SYS file. This program
              intercepts both INT 67H and INT 13H but does not use the
              stack separately. If CACHE.SYS is installed under
              some EMM driver that does not manage the stack by itself,
              PC-CACHE.COM will destroy the stack and hang up the machine.

          (2) CACHE.SYS will not use expanded memory under EMM software
              for the 286. If CACHE.SYS encounters EMM software, it will
              use extended memory but not expanded memory.



  <------------------ CACHE.SYS document file end ---------------------->
