4100 MT  (250-5160)    Upgrading The Microprocessor    Faxback Doc. # 2777

Your computer supports 80486SX, 80487SX, and 80486DX microprocessors with
speeds of 25 and 33 MHz, 80486DX2 microprocessors with speeds of 50 and 66
MHz, and the OverDrive (TM) for DX2 microprocessor with speeds of 50 and
66 MHz.

Warning:  Removing or installing the microprocessor without special tools
          can easily result in damage to the chips.  If you are not sure
          how to remove and insert a microprocessor, have a Radio Shack
          service center install it for you.

To upgrade the microprocessor, perform the following steps:

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

     2.  Locate the microprocessor socket on the system board.

     3.  Raise the chip edges slowly and very evenly until the chip is
         free.  Be careful not to bend the microprocessor pins.  Do not
         pull the chip edges with your finger, as this is likely to
         result in damage to the pins.  If at all possible, use a special
         extraction tool.  See your Radio Shack store or participating
         dealer for more information.  After you remove it, place the
         chip in proper anti-static material.

     4.  Align the new microprocessor pins with the socket.  Match pin
         1 of the microprocessor (indicated by a dot or beveled corner)
         with the beveled-corner marking etched on the system board.

Warning:  Not aligning the microprocessor correctly can permanently damage
          the cip and your system board.

     5.  Push down on the microprocessor until it is firmly inserted in
         the socket.

     6.  Locate jumpers E9-E13 on the system board.  Connect the
         jumper pins for your configuration as specified below.

                                 486DX       OverDrive        OverDrive
Jumper      486SX     487SX      486DX-2     for 486SX        for DX2

E9          Open*     1-2        2-3         1-2              1-2
E10         2-3       1-2        1-2         1-2              1-2
E11         1-2       2-3        1-2         2-3              2-3
E12         Open*     Closed*    Closed*     Closed*          Closed*
E13         2-3       2-3        2-3         2-3              1-2

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

     7.  Replace the internal drive bay and system-unit cover.  Reconnect
         peripheral devices, and plug in the power and phone cords.  Turn
         on the system.

(ALL/all-06/16/94)