Compaq 164SX - Manual (Page 37)

Power and Environmental Requirements 3–1
3
Power and Environmental Requirements
This chapter describes the AlphaPC 164SX power and environmental requirements,
and physical board parameters.
3.1 Power Requirements
The AlphaPC 164SX derives its main dc power from a user-supplied power supply.
The board has a total power dissipation of 90 W, excluding any plug-in PCI and ISA
devices. An onboard +5-V to +2.5-V dc-to-dc converter is designed to handle 24 A of
current. Table 3–1 lists the power requirement for each dc supply voltage.
The power supply must supply a dcok signal to the system reset logic. Refer to
Section 4.6 for additional information.
Caution: Fan sensor required. The 21164PC microprocessor cooling fan must
drive an RPM indicator signal. If the airflow stops, the sensor on the
motherboard detects that the RPM has stopped, and resets the system.
1
Values indicated are for an AlphaPC 164SX motherboard with an Alpha 21164PC microproces-
sor operating at 533 MHz, with 128MB SDRAM, excluding adapter cards and disk drives.
Table 3–1 Power Supply DC Current Requirements
Voltage/Tolerance Current 1
+3.3 V dc, ± 5% 5.0 A
+5 V dc, ± 5% 12.0 A
–5 V dc, ± 5% 0.0 A
+12 V dc, ± 5% 1.0 A
–12 V dc, ± 5% 100.0 mA