4833 LX/T (250-5145)         Upgrade Processor          Faxback Doc. # 2254

Note: The DX2 style processors are functionally the same, as an Overdrive
      processor. An overdrive processor will be marked "Overdrive" a DX2
      style will be marked 486DX2.

Your computer has a i486 DX style microprocessor; you can install a 486 DX2,
or an OverDrive Processor (66MHZ). The DX/2 and Overdrive processors will 
increase the internal clock speed of the CPU. The processor socket (U54) on
the main logic board allows easy installation of an upgrade Processor.

CAUTION: Double check the switch settings before installing the new chip.
         Incorrect installation of an upgrade processor can cause electrical
         damage to the main logic board or the component. If you choose not
         to perform this procedure, your computer dealer can do this for
         you.

┌─────────────────┐
│Switch Settings: │
└─────────────────┘
SW1 is a 4 position DIP switch block which is located on the main logic 
board.  Switches 1 and 2 configure the processor type.

  ┌──────────────┬──────────────┬──────────┬────────┐ 
  │ Processor    │ SWITCH 1     │ SWITCH 2 │ SOCKET │ 
  ├──────────────┼──────────────┼──────────┼────────┤ 
  │ 486SX        │ OFF          │ OFF      │ U54    │ 
  ├──────────────┼──────────────┼──────────┼────────┤ 
  │ 486DX        │ ON           │ OFF      │ U54    │ 
  ├──────────────┼──────────────┼──────────┼────────┤
  │ 487SX        │ ON           │ ON       │ U54    │  
  ├──────────────┼──────────────┼──────────┼────────┤
  │ 486 Overdrive│ ON           │ ON       │ U54    │ **
  ├──────────────┼──────────────┼──────────┼────────┤
  │ 486DX2/ODPR  │ ON           │ OFF      │ U54    │
  └──────────────┴──────────────┴──────────┴────────┘


    TCH 3 (Primary Video Display Adapter Type)
  ┌──────────┬──────────────────────────┐
  │ SWITCH 3 │    DISPLAY ADAPTER TYPE  │
  ├──────────┼──────────────────────────┤
  │    ON    │    color*                │
  ├──────────┼──────────────────────────┤
  │    OFF   │    monochrome            │
  ├──────────┴──────────────────────────┤
  │ * Indicates default setting.        │
  └─────────────────────────────────────┘


   ** The overdrive chip is currently the more accepted method of upgrading
      to 66 Mhz speeds.

Before you begin, carefully read the following steps and the documentation
provided with the component you are installing.

┌─────────────────────────────────┐
│To install an upgrade processor: │
└─────────────────────────────────┘

 1. Turn off the computer, and disconnect all cables.
 2. Discharge any accumulated static electricity from your body by touching
    a grounded metal object. Then, open the computer.
 3. Remove any expansion adapters installed in the expansion area by
    removing the expansion slot screws, disconnect any data cables,
    and gently move each adapter back and forth while pulling it out of the
    card connector.
 4. The original microprocessor is an i486 DX. 

Note: A special chip extraction tool is needed to remove the processor. If
      you do not have this tool, have a Radio Shack Service Center install
      the upgrade processor for you.

 5. Orient the upgrade processor so that the notch on the component aligns
    with Pin 1 of the processor socket.
 6. Taking care not to bend or touch the metal pins, press the component
    into the socket.
 7. Be sure the switch settings are properly set.
    (See chart above)
 8. Replace any expansion adapter you removed.
 9. Be sure internal cables are securely connected and do not cause
    mechanical interference. Then, close the computer.
10. Reconnect all cables.

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