ABIT COMPUTER CORPORATION
=========================

   VL-BUS 486 MAIN BOARD

   Processor         80486SX/80487SX/80486DX/80486DX2             
   Processor Speed   25/33/40/50(internal)/50/66(internal)MHz     
   Chip Set          UNI                                          
   Max. Onboard DRAM 32MB                                         
   Cache             64/128/256KB                                 
   BIOS              AMI/Award                                    
   Dimensions        330mm x 218mm                                
   I/O Options       32-bit VESA local bus slots (2)              

<gopher://bitreich.org/I/th99/m/S-T/35065-1.png>
   

   +------------------------------------------------------------+
   |                        CONNECTIONS                         |
   |------------------------------------------------------------|
   | Purpose       | Location | Purpose              | Location |
   |---------------+----------+----------------------+----------|
   | Power LED &   |   CN1    | External battery     |   CN6    |
   | keylock       |          |                      |          |
   |---------------+----------+----------------------+----------|
   | Speaker       |   CN3    | Reset switch         |   CN8    |
   |---------------+----------+----------------------+----------|
   | Turbo LED     |   CN4    | Power LED            |   LED1   |
   |---------------+----------+----------------------+----------|
   | Turbo switch  |   CN5    | 32-bit VESA local    | S1 & S2  |
   |               |          | bus slots            |          |
   +------------------------------------------------------------+

   +------------------------------------------------------------+
   |                 USER CONFIGURABLE SETTINGS                 |
   |------------------------------------------------------------|
   |               Function               | Jumper |  Position  |
   |--------------------------------------+--------+------------|
   |>> | CMOS memory normal               |  JP12  | pins 1 & 2 |
   |   |                                  |        |   closed   |
   |---+----------------------------------+--------+------------|
   |   | CMOS memory clear                |  JP12  | pins 2 & 3 |
   |   |                                  |        |   closed   |
   |---+----------------------------------+--------+------------|
   |>> | FAST A20 enabled                 |  JP17  | pins 1 & 2 |
   |   |                                  |        |   closed   |
   |---+----------------------------------+--------+------------|
   |   | FAST A20 disabled                |  JP17  | pins 2 & 3 |
   |   |                                  |        |   closed   |
   |---+----------------------------------+--------+------------|
   |>> | Monitor type select color        |  JP18  |   Closed   |
   |---+----------------------------------+--------+------------|
   |   | Monitor type select monochrome   |  JP18  |    Open    |
   |---+----------------------------------+--------+------------|
   |>> | Factory configured - do not      |  JP23  | pins 1 & 2 |
   |   | alter                            |        |   closed   |
   |---+----------------------------------+--------+------------|
   |>> | Factory configured - do not      |  JP24  | pins 1 & 2 |
   |   | alter                            |        |   closed   |
   |---+----------------------------------+--------+------------|
   |>> | Factory configured - do not      |  JP25  | pins 1 & 2 |
   |   | alter                            |        |   closed   |
   |---+----------------------------------+--------+------------|
   |>> | Factory configured - do not      |  JP26  | pins 2 & 3 |
   |   | alter                            |        |   closed   |
   |---+----------------------------------+--------+------------|
   |>> | Power good signal detect from    |  JP27  | pins 2 & 3 |
   |   | power supply                     |        |   closed   |
   |---+----------------------------------+--------+------------|
   |   | Power good signal detect from    |  JP27  | pins 1 & 2 |
   |   | board                            |        |   closed   |
   |---+----------------------------------+--------+------------|
   |>> | Factory configured - do not      |  JP28  | pins 2 & 3 |
   |   | alter                            |        |   closed   |
   +------------------------------------------------------------+

   +------------------------------------------------------------+
   |                     DRAM CONFIGURATION                     |
   |------------------------------------------------------------|
   |       Size       |       Bank 0       |       Bank 1       |
   |------------------+--------------------+--------------------|
   |       1MB        |    (4) 256K x 9    |        NONE        |
   |------------------+--------------------+--------------------|
   |       2MB        |    (4) 256K x 9    |    (4) 256K x 9    |
   |------------------+--------------------+--------------------|
   |       4MB        |     (4) 1M x 9     |        NONE        |
   |------------------+--------------------+--------------------|
   |       8MB        |     (4) 1M x 9     |     (4) 1M x 9     |
   |------------------+--------------------+--------------------|
   |       16MB       |     (4) 4M x 9     |        NONE        |
   |------------------+--------------------+--------------------|
   |       32MB       |     (4) 4M x 9     |     (4) 4M x 9     |
   +------------------------------------------------------------+

   +------------------------------------------------------------+
   |                    CACHE CONFIGURATION                     |
   |------------------------------------------------------------|
   | Size  | Bank 0  | Bank 1  |  TAG write   | TAG write back  |
   |       |         |         | through U15  |     U14,U15     |
   |-------+---------+---------+--------------+-----------------|
   | 64KB  | (4) 8K  | (4) 8K  |    8K x 8    |   (2) 8K x 8    |
   |       |   x 8   |   x 8   |              |                 |
   |-------+---------+---------+--------------+-----------------|
   | 128KB | (4) 32K |  NONE   |    8K x 8    |   (2) 8K x 8    |
   |       |   x 8   |         |              |                 |
   |-------+---------+---------+--------------+-----------------|
   | 256KB | (4) 32K | (4) 32K |   32K x 8    |   (2) 32K x 8   |
   |       |   x 8   |   x 8   |              |                 |
   +------------------------------------------------------------+

   +------------------------------------------------------------+
   |                 CACHE JUMPER CONFIGURATION                 |
   |------------------------------------------------------------|
   |   Size    | JP1  | JP2  | JP3  | JP4  | JP5  | JP6  | JP7  |
   |-----------+------+------+------+------+------+------+------|
   |   64KB    | N/A  | N/A  | 1 &  | 1 &  | 2 &  | 1 &  | 1 &  |
   |   write   |      |      |  2   |  2   |  3   |  2   |  2   |
   |  through  |      |      |      |      |      |      |      |
   |-----------+------+------+------+------+------+------+------|
   |   64KB    | 1 &  | 1 &  | 1 &  | 1 &  | 2 &  | 1 &  | 1 &  |
   |   write   |  2   |  2   |  2   |  2   |  3   |  2   |  2   |
   |   back    |      |      |      |      |      |      |      |
   |-----------+------+------+------+------+------+------+------|
   |   128KB   | N/A  | N/A  | 2 &  | 1 &  | 1 &  | 1 &  | 2 &  |
   |   write   |      |      |  3   |  2   |  2   |  2   |  3   |
   |  through  |      |      |      |      |      |      |      |
   |-----------+------+------+------+------+------+------+------|
   |   128KB   | 2 &  | 1 &  | 2 &  | 1 &  | 1 &  | 1 &  | 2 &  |
   |   write   |  3   |  2   |  3   |  2   |  2   |  2   |  3   |
   |   back    |      |      |      |      |      |      |      |
   |-----------+------+------+------+------+------+------+------|
   |   256KB   | N/A  | N/A  | 2 &  | 2 &  | 2 &  | 2 &  | 2 &  |
   |   write   |      |      |  3   |  3   |  3   |  3   |  3   |
   |  through  |      |      |      |      |      |      |      |
   |-----------+------+------+------+------+------+------+------|
   |   256KB   | 2 &  | 2 &  | 2 &  | 2 &  | 2 &  | 2 &  | 2 &  |
   |   write   |  3   |  3   |  3   |  3   |  3   |  3   |  3   |
   |   back    |      |      |      |      |      |      |      |
   |------------------------------------------------------------|
   | Note:Pins designated should be in the closed position.     |
   +------------------------------------------------------------+

   +------------------------------------------------------------+
   |                  CPU SPEED CONFIGURATION                   |
   |------------------------------------------------------------|
   |     Speed     |     JP20     |     JP21     |     JP22     |
   |---------------+--------------+--------------+--------------|
   |     25MHz     |    Closed    |     Open     |    Closed    |
   |---------------+--------------+--------------+--------------|
   |     33MHz     |     Open     |    Closed    |    Closed    |
   |---------------+--------------+--------------+--------------|
   |     40MHz     |    Closed    |     Open     |     Open     |
   |---------------+--------------+--------------+--------------|
   |    50iMHz     |    Closed    |     Open     |    Closed    |
   |---------------+--------------+--------------+--------------|
   |     50MHz     |     Open     |    Closed    |     Open     |
   |---------------+--------------+--------------+--------------|
   |    66iMHz     |     Open     |    Closed    |    Closed    |
   +------------------------------------------------------------+

   +------------------------------------------------------------+
   |                   CPU TYPE CONFIGURATION                   |
   |------------------------------------------------------------|
   |   CPU Type   |     JP13     |    JP14    |  JP15  |  JP16  |
   |--------------+--------------+------------+--------+--------|
   | 80486SX PGA  |     open     | pins 2 & 3 |  Open  | Closed |
   |              |              |   closed   |        |        |
   |--------------+--------------+------------+--------+--------|
   |   80486 SX   |     open     | pins 2 & 3 |  Open  |  Open  |
   |     PQFP     |              |   closed   |        |        |
   |--------------+--------------+------------+--------+--------|
   |   80487SX    |  pins 2 & 3  | pins 1 & 2 | Closed |  N/A   |
   |              |    closed    |   closed   |        |        |
   |--------------+--------------+------------+--------+--------|
   | 80486DX, DX2 |  pins 1 & 2  | pins 1 & 2 | Closed |  N/A   |
   |              |    closed    |   closed   |        |        |
   +------------------------------------------------------------+

   +------------------------------------------------------------+
   |          VESA WAIT STATE/BUS SPEED CONFIGURATION           |
   |------------------------------------------------------------|
   | CPU speed |    Wait    |  JP8   |  JP9   |  JP10  |  JP11  |
   |           |   states   |        |        |        |        |
   |-----------+------------+--------+--------+--------+--------|
   |  < 33MHz  |   0 wait   | pins 1 | pins 1 | pins 1 | pins 1 |
   |           |   states   |  & 2   |  & 2   |  & 2   |  & 2   |
   |-----------+------------+--------+--------+--------+--------|
   |  > 33MHz  |   1 wait   | pins 2 | pins 2 | pins 2 | pins 2 |
   |           |   state    |  & 3   |  & 3   |  & 3   |  & 3   |
   |------------------------------------------------------------|
   | Note: Pins designated should be in the closed position.    |
   +------------------------------------------------------------+