Specifications

9 March 1999 – Subject To Change Power and Environmental Requirements 3–1
3
Power and Environmental Requirements
This chapter describes the AlphaPC 164LX power and environmental requirements,
and physical board parameters.
3.1 Power Requirements
The AlphaPC 164LX derives its main dc power from a user-supplied power supply.
The board has a total power dissipation of 100 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, and schematic pages pc164lx.29 and pc164lx.30 for additional infor-
mation.
Caution: Fan Sensor Required. The 21164 microprocessor cooling fan must
have a built-in sensor that will drive a signal if the airflow stops. The
sensor is connected to AlphaPC 164LX board connector J18. When the
signal is generated, it resets the system.
Table 3–1 Power Supply DC Current Requirements
Voltage/Tolerance Current
1
1
Values indicated are for an AlphaPC 164LX motherboard with an Alpha 21164 microprocessor
operating at 600 MHz, with 64MB SDRAM, excluding adapter cards and disk drives.
+3.3 V dc, ±5% 5.0 A
+5 V dc,
±5% 14.0 A
–5 V dc,
±5% 0 A
+12 V dc,
±5% 1.0 A
–12 V dc,
±5% 100.0 mA