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# TANDY/RADIO SHACK
425SX, 433SX, 433DX, 450DX2, 466DX2
Processor 80486SX/ODP486SX/80487SX/80486DX/ODP486SX/80486DX2
Processor 25/33/50(internal)/66(internal)MHz
Speed
Chip Set Unidentified
Video Chip Unidentified
Set
Maximum 40MB
Onboard
Memory
Maximum 1MB
Video
Memory
Cache 64/128/256KB
BIOS Phoenix
Dimensions 330mm x 218mm
I/O Options Floppy drive interface, IDE interface, parallel
port, PS/2 mouse port, serial ports (2), VGA
feature connector, VGA port, riser slot
NPU Options None
IMG IMG 1
+------------------------------------------------------------+
| CONNECTIONS |
|------------------------------------------------------------|
| Purpose | Location | Purpose | Location |
|-----------------+----------+--------------------+----------|
| VGA port | CN1 | External battery | J7 |
|-----------------+----------+--------------------+----------|
| Parallel port | CN2 | IDE interface | J17 |
|-----------------+----------+--------------------+----------|
| Serial port 1 | CN3 | Floppy drive | J18 |
| | | interface | |
|-----------------+----------+--------------------+----------|
| Serial port 2 | CN4 | VGA feature | J21 |
| | | connector | |
|-----------------+----------+--------------------+----------|
| PS/2 mouse port | CN5 | Riser slot | SL1 |
+------------------------------------------------------------+
+------------------------------------------------------------+
| USER CONFIGURABLE SETTINGS |
|------------------------------------------------------------|
| Function | Label | Position |
|---------------------------------------+-------+------------|
| » | Factory configured - do not alter | J9 | Pins 1 & 2 |
| | | | closed |
|---+-----------------------------------+-------+------------|
| » | Factory configured - do not alter | J11 | Open |
|---+-----------------------------------+-------+------------|
| » | Factory configured - do not alter | J13 | Pins 1 & 2 |
| | | | closed |
|---+-----------------------------------+-------+------------|
| » | Factory configured - do not alter | J14 | Pins 2 & 3 |
| | | | closed |
|---+-----------------------------------+-------+------------|
| » | CMOS memory normal operation | J20 | Closed |
|---+-----------------------------------+-------+------------|
| | CMOS memory clear | J20 | Open |
|---+-----------------------------------+-------+------------|
| » | On board video enabled | J28 | Pins 2 & 3 |
| | | | closed |
|---+-----------------------------------+-------+------------|
| | On board video disabled | J28 | Pins 1 & 2 |
| | | | closed |
|---+-----------------------------------+-------+------------|
| » | Factory configured - do not alter | J29 | Open |
|---+-----------------------------------+-------+------------|
| » | Floppy drive write protect | J30 | Pins 2 & 3 |
| | disabled | | closed |
|---+-----------------------------------+-------+------------|
| | Floppy drive write protect | J30 | Pins 1 & 2 |
| | enabled | | closed |
|---+-----------------------------------+-------+------------|
| » | Factory configured - do not alter | J31 | Pins 2 & 3 |
| | | | closed |
|---+-----------------------------------+-------+------------|
| » | Zero wait state enabled | J32 | Closed |
|---+-----------------------------------+-------+------------|
| | Zero wait state disabled | J32 | Open |
+------------------------------------------------------------+
+------------------------------------------------------------+
| DRAM CONFIGURATION |
|------------------------------------------------------------|
| Size | Bank 0 | Bank 1 | Bank 2 |
|------------+---------------+---------------+---------------|
| 1MB | (1) 256K x 36 | None | None |
|------------+---------------+---------------+---------------|
| 2MB | None | (4) 256K x 9 | (4) 256K x 9 |
|------------+---------------+---------------+---------------|
| 2MB | (1) 512K x 36 | None | None |
|------------+---------------+---------------+---------------|
| 4MB | None | (4) 1M x 9 | None |
|------------+---------------+---------------+---------------|
| 4MB | (1) 1M x 36 | None | None |
|------------+---------------+---------------+---------------|
| 5MB | None | (4) 1M x 9 | (4) 256K x 9 |
|------------+---------------+---------------+---------------|
| 6MB | (1) 512K x 36 | (4) 1M x 9 | None |
|------------+---------------+---------------+---------------|
| 8MB | (1) 1M x 36 | (4) 1M x 9 | None |
|------------+---------------+---------------+---------------|
| 8MB | (1) 2M x 36 | None | None |
|------------+---------------+---------------+---------------|
| 8MB | None | (4) 1M x 9 | (4) 1M x 9 |
|------------+---------------+---------------+---------------|
| 10MB | (1) 512K x 36 | (4) 1M x 9 | (4) 1M x 9 |
|------------+---------------+---------------+---------------|
| 12MB | (1) 1M x 36 | (4) 1M x 9 | (4) 1M x 9 |
|------------+---------------+---------------+---------------|
| 12MB | (1) 2M x 36 | (4) 1M x 9 | None |
|------------+---------------+---------------+---------------|
| 16MB | (1) 2M x 36 | (4) 1M x 9 | (4) 1M x 9 |
|------------+---------------+---------------+---------------|
| 16MB | None | (4) 4M x 9 | None |
+------------------------------------------------------------+
+------------------------------------------------------------+
| DRAM CONFIGURATION (CON’T) |
|------------------------------------------------------------|
| Size | Bank 0 | Bank 1 | Bank 2 |
|------------+---------------+---------------+---------------|
| 17MB | None | (4) 4M x 9 | (4) 256K x 9 |
|------------+---------------+---------------+---------------|
| 18MB | (1) 512K x 36 | (4) 4M x 9 | None |
|------------+---------------+---------------+---------------|
| 20MB | (1) 1M x 36 | (4) 4M x 9 | None |
|------------+---------------+---------------+---------------|
| 20MB | None | (4) 4M x 9 | (4) 1M x 9 |
|------------+---------------+---------------+---------------|
| 22MB | (1) 512K x 36 | (4) 4M x 9 | (4) 1M x 9 |
|------------+---------------+---------------+---------------|
| 24MB | (1) 1M x 36 | (4) 4M x 9 | (4) 1M x 9 |
|------------+---------------+---------------+---------------|
| 24MB | (1) 2M x 36 | (4) 4M x 9 | None |
|------------+---------------+---------------+---------------|
| 28MB | (1) 2M x 36 | (4) 4M x 9 | (4) 1M x 9 |
|------------+---------------+---------------+---------------|
| 32MB | None | (4) 4M x 9 | (4) 4M x 9 |
|------------+---------------+---------------+---------------|
| 34MB | (1) 512K x 36 | (4) 4M x 9 | (4) 4M x 9 |
|------------+---------------+---------------+---------------|
| 36MB | (1) 1M x 36 | (4) 4M x 9 | (4) 4M x 9 |
|------------+---------------+---------------+---------------|
| 40MB | (1) 2M x 36 | (4) 4M x 9 | (4) 4M x 9 |
+------------------------------------------------------------+
+------------------------------------------------------------+
| CACHE CONFIGURATION |
|------------------------------------------------------------|
| Size | Bank 0 | Bank 1 | TAG | U1 |
|-------+-------------+------------+-------------+-----------|
| 64KB | (4) 8K x 8 | (4) 8K x 8 | (1) 8K x 8 | (1) 64K x |
| | | | | 1 |
|-------+-------------+------------+-------------+-----------|
| 128KB | (4) 32K x 8 | None | (1) 8K/32K | (1) 64K x |
| | | | x 8 | 1 |
|-------+-------------+------------+-------------+-----------|
| 256KB | (4) 32K x 8 | (4) 32K x | (1) 32K x 8 | (1) 64K x |
| | | 8 | | 1 |
+------------------------------------------------------------+
+------------------------------------------------------------+
| CACHE JUMPER CONFIGURATION |
|------------------------------------------------------------|
| Size | J16 |
|------------------+-----------------------------------------|
| None | Pins 1 & 2, 3 & 4, 5 & 6, 9 & 10 closed |
|------------------+-----------------------------------------|
| 64KB | Open |
|------------------+-----------------------------------------|
| 128KB | Pins 1 & 2, 5 & 6, 7 & 8 closed |
|------------------+-----------------------------------------|
| 256KB | Pins 1 & 2, 3 & 4, 5 & 6, 9 & 10 closed |
+------------------------------------------------------------+
+------------------------------------------------------------+
| VIDEO MEMORY CONFIGURATION |
|------------------------------------------------------------|
| Size | Bank 0 | Bank 1 |
|--------------------+-------------------+-------------------|
| 512KB | 512KB | None |
|--------------------+-------------------+-------------------|
| 1MB | 512KB | 512KB |
|------------------------------------------------------------|
| Note: The size of the video memory chips are unidentified. |
+------------------------------------------------------------+
+------------------------------------------------------------+
| CPU SPEED SELECTION |
|------------------------------------------------------------|
| Speed | J26 | J27 |
|------------------+--------------------+--------------------|
| 25MHz | Pins 1 & 2 closed | Pins 2 & 3 closed |
|------------------+--------------------+--------------------|
| 33MHz | Pins 1 & 2 closed | Pins 1 & 2 closed |
|------------------+--------------------+--------------------|
| 50iMHz | Pins 1 & 2 closed | Pins 2 & 3 closed |
|------------------+--------------------+--------------------|
| 66iMHz | Pins 1 & 2 closed | Pins 1 & 2 closed |
+------------------------------------------------------------+
+------------------------------------------------------------+
| CPU TYPE SELECTION |
|------------------------------------------------------------|
| Type | J19 |
|----------------------------+-------------------------------|
| 80486SX | Pins 1 & 3, 2 & 4 closed |
|----------------------------+-------------------------------|
| ODP486SX | Pins 1 & 3, 2 & 4 closed |
|----------------------------+-------------------------------|
| 80487SX | Pins 1 & 3, 2 & 4 closed |
|----------------------------+-------------------------------|
| 80486DX | Pins 3 & 5, 4 & 6 closed |
|----------------------------+-------------------------------|
| ODP486DX | Pins 3 & 5, 4 & 6 closed |
|----------------------------+-------------------------------|
| 80486DX2 | Pins 3 & 5, 4 & 6 closed |
+------------------------------------------------------------+