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# TANDY/RADIO SHACK
4820ST/T (250-5140)
Processor 80486SX/80487SX/ODP486/ODPR486/80486DX/80486DX2
Processor 20/25/33/40/50(internal)/50/66(internal)MHz
Speed
Chip Set Unidentified
Video Chip Set None
Maximum 64MB
Onboard Memory
Maximum Video None
Memory
Cache None
BIOS Unidentified
Dimensions 330mm x 218mm
I/O Options Floppy drive interface, IDE interface, parallel
port, PS/2 mouse port, serial ports (2)
NPU Options 80487SX
IMG IMG 1
+------------------------------------------------------------+
| CONNECTIONS |
|------------------------------------------------------------|
| Purpose | Location | Purpose | Location |
|-------------------+----------+------------------+----------|
| PS/2 mouse port | CN1 | IDE interface | CN6 |
|-------------------+----------+------------------+----------|
| Serial port 1 | CN2 | Power indicator | J1 |
|-------------------+----------+------------------+----------|
| Serial port 2 | CN3 | IDE interface | J2 |
| | | LED | |
|-------------------+----------+------------------+----------|
| Parallel port | CN4 | External battery | J3 |
|-------------------+----------+------------------+----------|
| Floppy drive | CN5 | Front panel | J4 |
| interface | | connector | |
+------------------------------------------------------------+
+------------------------------------------------------------+
| USER CONFIGURABLE SETTINGS |
|------------------------------------------------------------|
| Function | Label | Position |
|-------------------------------------+-------+--------------|
| » | CMOS memory normal operation | JP1 | Open |
|---+---------------------------------+-------+--------------|
| | CMOS memory clear | JP1 | Closed |
|---+---------------------------------+-------+--------------|
| » | Monitor type select color | SW1/3 | On |
|---+---------------------------------+-------+--------------|
| | Monitor type select monochrome | SW1/3 | Off |
|---+---------------------------------+-------+--------------|
| » | Factory configured - do not | SW1/4 | Unidentified |
| | alter | | |
+------------------------------------------------------------+
+------------------------------------------------------------+
| DRAM CONFIGURATION |
|------------------------------------------------------------|
| Size | Bank 0 | Bank 1 | Bank 2 | Bank 3 |
|------+-------------+-------------+------------+------------|
| 1MB | (4) 256K x | None | None | None |
| | 9 | | | |
|------+-------------+-------------+------------+------------|
| 2MB | (4) 256K x | (4) 256K x | None | None |
| | 9 | 9 | | |
|------+-------------+-------------+------------+------------|
| 3MB | (4) 256K x | (4) 256K x | (4) 256K x | None |
| | 9 | 9 | 9 | |
|------+-------------+-------------+------------+------------|
| 4MB | (4) 256K x | (4) 256K x | (4) 256K x | (4) 256K x |
| | 9 | 9 | 9 | 9 |
|------+-------------+-------------+------------+------------|
| 4MB | (4) 1M x 9 | None | None | None |
|------+-------------+-------------+------------+------------|
| 5MB | (4) 256K x | (4) 1M x 9 | None | None |
| | 9 | | | |
|------+-------------+-------------+------------+------------|
| 6MB | (4) 256K x | (4) 256K x | (4) 1M x 9 | None |
| | 9 | 9 | | |
|------+-------------+-------------+------------+------------|
| 8MB | (4) 1M x 9 | (4) 1M x 9 | None | None |
|------+-------------+-------------+------------+------------|
| 9MB | (4) 1M x 9 | (4) 1M x 9 | (4) 256K x | None |
| | | | 9 | |
|------+-------------+-------------+------------+------------|
| 10MB | (4) 256K x | (4) 256K x | (4) 1M x 9 | (4) 1M x 9 |
| | 9 | 9 | | |
|------+-------------+-------------+------------+------------|
| 12MB | (4) 1M x 9 | (4) 1M x 9 | (4) 1M x 9 | None |
|------+-------------+-------------+------------+------------|
| 16MB | (4) 1M x 9 | (4) 1M x 9 | (4) 1M x 9 | (4) 1M x 9 |
|------+-------------+-------------+------------+------------|
| 16MB | (4) 4M x 9 | None | None | None |
|------+-------------+-------------+------------+------------|
| 17MB | (4) 256K x | (4) 4M x 9 | None | None |
| | 9 | | | |
|------+-------------+-------------+------------+------------|
| 18MB | (4) 256K x | (4) 256K x | (4) 4M x 9 | None |
| | 9 | 9 | | |
|------+-------------+-------------+------------+------------|
| 20MB | (4) 1M x 9 | (4) 4M x 9 | None | None |
|------+-------------+-------------+------------+------------|
| 24MB | (4) 1M x 9 | (4) 1M x 9 | (4) 4M x 9 | None |
|------+-------------+-------------+------------+------------|
| 32MB | (4) 4M x 9 | (4) 4M x 9 | None | None |
|------+-------------+-------------+------------+------------|
| 33MB | (4) 4M x 9 | (4) 4M x 9 | (4) 256K x | None |
| | | | 9 | |
|------+-------------+-------------+------------+------------|
| 34MB | (4) 256K x | (4) 256K x | (4) 4M x 9 | (4) 4M x 9 |
| | 9 | 9 | | |
|------+-------------+-------------+------------+------------|
| 36MB | (4) 4M x 9 | (4) 4M x 9 | (4) 1M x 9 | None |
|------+-------------+-------------+------------+------------|
| 40MB | (4) 1M x 9 | (4) 1M x 9 | (4) 4M x 9 | (4) 4M x 9 |
|------+-------------+-------------+------------+------------|
| 48MB | (4) 4M x 9 | (4) 4M x 9 | (4) 4M x 9 | None |
|------+-------------+-------------+------------+------------|
| 64MB | (4) 4M x 9 | (4) 4M x 9 | (4) 4M x 9 | (4) 4M x 9 |
+------------------------------------------------------------+
+------------------------------------------------------------+
| CPU TYPE SELECTION |
|------------------------------------------------------------|
| Type | Socket | SW1/1 | SW1/2 |
|---------------+---------------+--------------+-------------|
| 80486SX | CPU | Off | Off |
|---------------+---------------+--------------+-------------|
| ODP486 | CPU | On | On |
|---------------+---------------+--------------+-------------|
| ODP486 | NPU | Off | Off |
|---------------+---------------+--------------+-------------|
| ODPR486 | CPU | On | Off |
|---------------+---------------+--------------+-------------|
| 80487SX | CPU | On | On |
|---------------+---------------+--------------+-------------|
| 80487SX | NPU | Off | Off |
|---------------+---------------+--------------+-------------|
| 80486DX | CPU | On | Off |
|---------------+---------------+--------------+-------------|
| 80486DX2 | CPU | On | Off |
+------------------------------------------------------------+