IBM 5160  -  Power Measurements

General

The IBM 5160's power supply is rated at 130 Watts. Expressed that way, the wattage is misleading. For example, it does not mean that 130 Watts of power can be drawn from the +5V line if no power is drawn from the other lines. Each of the output voltage lines has its own power rating, that must not be exceeded. Click here to see those ratings.

A consideration when calculating power consumption is that the peak of power consumption for each device can occur at different times. The diagram here shows an example for the +12V line.

Power measurements

The power consumption figures shown below were determined by measuring current consumption from the power supply.

Current consumption was measured using a digital multimeter and altered power cables. Of those cables, the cable used to measure motherboard current and expansion card current is shown on this link.

Because of 1. the limitations of measuring complex current consumption using a digital multimeter, and 2. small variations between units, the figures shown below should only be used as a guide.

IBM 5160 MOTHERBOARD - 640KB VERSION

If your motherboard has the optional 8087 math coprocessor fitted, see note 1.

Measured
AMPS
- Normal
Measured
AMPS
- Peak
Calculated
WATTS
- Normal
Calculated
WATTS
- Peak
Comment
+5 V 1.45 A 1.5 A 7.25 W 7.5 W Peak occurs on application of power. No 8087 math coprocessor.
- 5 V 0 0 0 0 Motherboard passes this through to expansion connectors.
+12 V 0 0 0 0 Motherboard passes this through to expansion connectors.
-12 V 0 0 0 0 Motherboard passes this through to expansion connectors.
= 7.25 W = 7.5 W

IBM KEYBOARD

Measured
AMPS
- Normal
Measured
AMPS
- Peak
Calculated
WATTS
- Normal
Calculated
WATTS
- Peak
Comment
+5 V 0.1 A 0.11 A 0.5 W 0.55 W Peak occurs on application of power.
= 0.5 W = 0.55 W

IBM 5.25" DISKETTE DRIVE ADAPTER  (360KB FLOPPY CONTROLLER)

Measured
AMPS
- Normal
Measured
AMPS
- Peak
Calculated
WATTS
- Normal
Calculated
WATTS
- Peak
Comment
+5 V 0.4 A 0.4 A 2 W 2 W
- 5 V 0 0 0 0 Later version of the adapter. See note 2.
+12 V 0 0 0 0 Circuit diagram indicates nil use.
-12 V 0 0 0 0 Circuit diagram indicates nil use.
= 2 W = 2 W

TANDON TM100-2 FULL HEIGHT FLOPPY DRIVE

Measured
AMPS
- Normal
Measured
AMPS
- Peak
Calculated
WATTS
- Normal
Calculated
WATTS
- Peak
Comment
+5 V 0.29 A 0.38 A 1.45 W 1.9 W Peak occurs during activation of spindle motor.
+12 V 0.34 A 0.9 A 4 W 10.8 W Peak occurs during activation of spindle motor.
= 5.45 W = 12.7 W

SEAGATE ST-412

Measured
AMPS
- Normal
Measured
AMPS
- Peak
Calculated
WATTS
- Normal
Calculated
WATTS
- Peak
Comment
+5 V 0.8 A 0.8 A 4 W 4 W One Seagate ST-412 spec indicates 1.1A
+12 V 1.25 A 3.1 A 15 W 37 W One Seagate ST-412 spec indicates 1.7A/3.5A
= 19 W = 41 W

 Note 1 At power on of the computer, and whilst idle, the 8087 draws about 1 W. [source: my measurement] When the 8087 is being used (a program is using it), the 8087 draws up to about 3 W. [source: 8087 datasheet] Note 2 IBM 5160s were fitted with the later version of the adapter, and that version does not use minus 5 volts. Click here to view the difference between the early and later adapters.