4100 MT  (250-5160)      Installing Cache Memory       Faxback Doc. # 2691

In addition to internal cache on the 80486 microprocessor, your system
supports external, secondary cache in sizes of 64KB and 256KB.  A
256-KB cache is necessary to cache system memory above 16MB.

Cache memory consists of two sets of chips:  cache and tag memory.  The
first set consists of eight 8-KB-x-8 SRAM chips for a 64-KB cache size,
or eight 32-KB-x-8 SRAM chips for a 256-KB cache size.

   64K External Cache Part # AX259-7230
  256K External Cache Part # AX259-7232

NOTE: The memory kits listed above are orderable from National Parts.

To install cache memory, do the following:

     1.  Turn the computer off, unplug the power and phone cords, and
         disconnect all peripheral devices.  Remove the system-unit cover,
         and move the internal drive bay.

     2.  Locate the sockets at U3, U4, and U11, U12, U16, U17, U21,
         and U22 on the system board.  Align the pins on a cache chip
         with a socket.  Push down on the chip until it is firmly
         inserted in the socket.  Repeat until all cache memory chips
         are installed.

     3.  Set jumpers E7 and E8, depending on the type of cache installed.
         See table below for cache jumper settings.

             Jumper      64-KB Cache      256-KB Cache

             E7          Open             Closed
             E8          Open             Closed

         Note:  A jumper is open if its pins are not
                connected; a closed jumper has its pins
                connected.

     4.  Install the tag memory chip at U30.  Use an 8-KB-x-9 SRAM
         for the 64-KB cache size, or a 32-KB-x-9 SRAM for the 256-KB
         cache size.

Warning:  If you are installing an 8 KBx9 SRAM, be sure to position
          the end of the chip that contains pins closer to the SIMMs
          than to the expansion slots.

     5.  Replace the internal drive bay and system-unit cover.
         Reconnect peripheral devices and plug in the power cord.
         Turn on the system.

(ALL/jej-08/15/94)