The IBM Personal Computer 5150 was equiped with one of two revisions of its main system board throughout its production:
- Up to March 1983, the 16-64KB board
- From March 1983, the 64-256KB board
A hand-made prototype IBM 5150 system board
16-64KB System Board
64-256KB System Board
Common Specification
- Intel 8088 CPU at 4.77MHz
- Socket for Intel 8087 FPU
- 5 ISA slots
- 4 banks of 9-bit (parity) RAM:
- For 16-64KB board - using 16 kbit chips
- For 64-256KB board - using 64 kbit chips
- Physically 9" x 13"
- DIN connectors for keyboard and cassette deck
BIOS Revisions
Configuration
The system configuration was set using two DIP switches.
Switch Block 1
This block is nearest the centre of the board.
| Boot |
Intel 8087
|
| Sw1
|
Boot from
|
| ON |
ROM (Cassette) BASIC
|
| OFF |
Floppy Disk
|
|
| Sw2
|
Intel 8087
|
| ON |
Not installed
|
| OFF |
Installed
|
|
| Memory |
Video |
Floppy Drives
|
| Sw3
|
Sw4
|
Banks Installed
|
| ON |
ON |
One bank
|
| OFF |
ON |
Two banks
|
| ON |
OFF |
Three banks
|
| OFF |
OFF |
Four banks
|
|
| Sw5
|
Sw6
|
Video Type
|
| ON |
ON |
No video or special (EGA, VGA)
|
| OFF |
ON |
40 column CGA
|
| ON |
OFF |
80 column CGA
|
| OFF |
OFF |
MDA (or Hercules) Video
|
|
| Sw7
|
Sw8
|
Floppy Drives
|
| ON |
ON |
1 drive
|
| OFF |
ON |
2 drives
|
| ON |
OFF |
3 drives
|
| OFF |
OFF |
4 drives
|
|
Switch Block 2
This block is nearest the CPU. Switches 1-5 define the total amount of memory installed (including that on expansion cards), and switchs 6-8 are always off.
| Total RAM Installed
|
Sw1
|
Sw2
|
Sw3
|
Sw4
|
Sw5
|
| 16K |
ON |
ON |
ON |
ON |
ON
|
| 32K |
ON |
ON |
ON |
ON |
ON
|
| 48K |
ON |
ON |
ON |
ON |
ON
|
| 64K |
ON |
ON |
ON |
ON |
ON
|
| 96K |
OFF |
ON |
ON |
ON |
ON
|
| 128K |
ON |
OFF |
ON |
ON |
ON
|
| 160K |
OFF |
OFF |
ON |
ON |
ON
|
| 192K |
ON |
ON |
OFF |
ON |
ON
|
| 224K |
OFF |
ON |
OFF |
ON |
ON
|
| 256K |
ON |
OFF |
OFF |
ON |
ON
|
| 288K |
OFF |
OFF |
OFF |
ON |
ON
|
| 320K |
ON |
ON |
ON |
OFF |
ON
|
| 352K |
OFF |
ON |
ON |
OFF |
ON
|
| 384K |
ON |
OFF |
ON |
OFF |
ON
|
| 416K |
OFF |
OFF |
ON |
OFF |
ON
|
| 448K |
ON |
ON |
OFF |
OFF |
ON
|
| 480K |
OFF |
ON |
OFF |
OFF |
ON
|
| 512K |
ON |
OFF |
OFF |
OFF |
ON
|
| 544K |
OFF |
OFF |
OFF |
OFF |
ON
|
| 576K |
ON |
ON |
ON |
ON |
OFF
|
| 608K |
OFF |
ON |
ON |
ON |
OFF
|
| 640K |
ON |
OFF |
ON |
ON |
OFF
|
See Also
