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# 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)
IMG IMG 1
+------------------------------------------------------------+
| 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. |
+------------------------------------------------------------+