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Equipment Log and Worksheets 59
Current Usage
As an overall current usage limitation on the power supply, do not exceed a combined power
output of 167 watts for the +5 V and +3.3 V outputs.
Calculating Power Usage
The total combined wattage for the system configuration must be less than 300 watts. Use the
two worksheets in this section to calculate the total used by your system. For current and voltage
requirements of add-in boards and peripherals, see your vendor documents.
Worksheet, Calculating DC Power Usage
1. List the current for each board and device in the appropriate voltage level column.
2. Add the currents in each column. Then go to the next worksheet.
Table 10. Power Usage Worksheet 1
Current (maximum) at voltage level:
Device +3.3 V +5 V –5 V +12 V –12 V
Boards, processors, and memory (get
totals from your board manual)
SCSI backplane
Front panel board
3.5-inch diskette drive
CD-ROM drive
Second 5.25-inch device
1st hot-swap hard drive
2nd hot-swap hard drive
3rd hot-swap hard drive
4th hot-swap hard drive
5th hot-swap hard drive
1st IDE hard drive
2nd IDE hard drive
Cooling fan 1, 92 mm 0.4 A
Cooling fan 2, 92 mm 0.4 A
Cooling fan 3, 92 mm 0.4 A
Total Current
Maximum Ratings (for comparison) 16.0 A 26.0 A 0.25 A 10.0 A 0.5 A