IBM 5160  -  Motherboard Switch/Jumper Settings

On versus off

For the switches, some people are unsure about which position is on and which position is off.
If you are unsure, then click here to see examples.

Switch block SW1

These settings apply to both versions of the 5160 motherboard, and apply to all three BIOS revisions for the 5160.

Switch 1: 
OFF:  Normal setting
ON:  Continuously perform the Power On Self Test (POST)
Switch 2: 
OFF:  8087 math coprocessor chip is installed
ON:  8087 math coprocessor chip is not installed
 • 8087 sits in IC socket U4, adjacent to power connectors.
Switches 3 and 4:   Enabled motherboard RAM.
3=ON , 4=ON :  Enable only bank 0
3=OFF, 4=ON :  Enable only banks 0/1
3=ON , 4=OFF:  Enable only banks 0/1/2
 3=OFF, 4=OFF:  Enable banks 0/1/2/3
 • Click here to see a diagram that shows the four RAM banks.
Switches 5 and 6:   Video card type.
5=OFF, 6=OFF:  MDA (monochrome)
5=OFF, 6=ON :  CGA, at 40 column by 25 line mode
5=ON , 6=OFF:  CGA, at 80 column by 25 line mode
5=ON , 6=ON :  Cards with a BIOS expansion ROM (e.g.  EGA / PGC / VGA)
 • For VGA card compatibility, click here.
Switches 7 and 8:   Floppy drive count.
7=ON , 8=ON :  1 floppy drive
7=OFF, 8=ON :  2 floppy drives
7=ON , 8=OFF:  3 floppy drives
7=OFF, 8=OFF:  4 floppy drives

Capacitor C1

The end of a small screwdriver fits into the slot on the top of the adjustable capacitor.

When using a composite monitor (or TV) as the display, adjusting the capacitor fine tunes the colours that appear.  Adjusting the capacitor does not affect the colours that appear on a digital monitor (MDA/CGA/EGA).

The capacitor's adjustable value is 5-30 pF.  If you need to replace the capacitor, and are having trouble finding a suitable replacement, then consider using a fixed value capacitor of say, 20 pF.  (Diagram)

Technical: Fine tunes the motherboard 14.31818 MHz clock signal, which in turn, fine tunes the NTSC 3.579545 MHz colour burst signal that the CGA card sends to the NTSC composite monitor.  (Diagram)