The IBM PC/XT model 5160 and the IBM Portable Computer shared a system board and various other components.
Specification
- Intel 8088 CPU at 4.77MHz
- Socket for Intel 8087 FPU
- 8 ISA slots (see also IBM Personal Computer XT System Board Slot 8)
- 4 banks of 9-bit (parity) RAM, using 64 kbit chips
- Physically 9" x 13"
- First version (c.1983) supported 64 to 256K RAM via 64 kbit chips (U84 is unpopulated)
- Second version (c.1986) supported 256 to 640K RAM by supporting 256 kbit RAM chips (U84 is populated with an 74LS158 chip).
BIOS Versions
- 16-Aug-1982 - First release, possibly never made it to production.
- ROM SIZE = 40K
- U18 = 32K chip labeled with IBM part number of 5000026. Contains BIOS and part of BASIC.
- U19 = 8K chip labeled with IBM part number of 5000027. Contains remainder of BASIC.
- 08-Nov-1982 - Second release.
- ROM SIZE = 40K
- U18 = 32K chip
- U19 = 8K chip
- Chips had part codes U18=1501512 and U19=500027, or U18=1501512 and U19=6359116
- 10-Jan-1086
- ROM SIZE = 64K
- U18 = 32K chip
- U19 = 32K chip
- Chips had part codes U18=62X0851 and U19=62X0854 (PROM), or U18=62X0852 and U19=62X0853 (EPROM)
- Used on 256/640K motherboards. Up to 640K RAM.
- Enhanced POST (one known enhancement is a faster test of RAM).
- Added support for the 101-key Enhanced keyboard.
- Support for 720K and 1.2M floppy drives (although the PC/XT never had a high-density controller).
Configuration
The system was configured using a set of DIP switches (there was no BIOS utility or NVRAM).
General System Configuration
| Switch
|
On
|
Off
|
| 1
|
POST loop test
|
Normal operation
|
| 2
|
Coprocessor not installed
|
Coprocessor installed
|
| 3,4
|
See memory table
|
See memory table
|
| 5,6
|
See video table
|
See video table
|
| 7,8
|
See floppy table
|
See floppy table
|
Memory Configuration
| Banks Occupied
|
Sw3
|
Sw4
|
| Bank 0 only
|
on
|
on
|
| Banks 0 and 1
|
off
|
on
|
| Banks 0, 1 and 2
|
on
|
off
|
| All 4 banks
|
off
|
off
|
|
Video Configuration
| Adapter Type
|
Sw5
|
Sw6
|
| Add-in card with BIOS
|
on
|
on
|
| CGA, 40x25
|
off
|
on
|
| CGA, 80x25
|
on
|
off
|
| Monochrome
|
off
|
off
|
|
Floppy Drive Configuration
| Drives Installed
|
Sw7
|
Sw8
|
| One
|
on
|
on
|
| Two
|
off
|
on
|
| Three
|
on
|
off
|
| Four
|
off
|
off
|
|
RAM
The system was fitted with either 64Kb 200ns 'IBM 4164-20' DRAM chips (first version) in four banks of nine chips (due to the RAM being in an ECC configuration), or 256 kbit chips (second version).
Various modifications were possible to increase the RAM capacity beyond 256K, including a custom decoder PROM to enable a 1MB configuration or using an ISA card.
- P1 - Power
- P2 - Power
- P3 - Speaker
Beep Codes
Some problems will be signal via 'beep-codes', assuming the speaker is connected and functional:
| Beep
|
Problem
|
| None
|
PSU, System board, Disconnected CPU (or speaker), or Grounded Keyboard Data Line
|
| Repeating short
|
PSU, System Board, or Keyboard
|
| 1 short
|
Normal POST (system is OK)
|
| 2 short
|
POST error (code shown on screen)
|
| 1 long, 1 short
|
System Board
|
| 1 long, 2 short
|
Display Adapter (MDA or CGA)
|
| 1 long, 3 short
|
Display Adapter (EGA)
|
| 3 long
|
3270 Keyboard Card
|
| Continuous
|
PSU, System Board, or Keyboard
|
See Also
