User`s guide

5
Board Requirements and Parameters
This chapter describes the evaluation board power and environmental
requirements, and physical board parameters.
5.1 Power Requirements
The AlphaPC64 derives its main dc power from a user-supplied, industry-
standard PC power supply. The board has a total power dissipation of 96.2 W,
excluding PCI and ISA devices. Table 5–1 lists the power requirements of each
dc supply voltage.
The power supply must supply signal p_dcok to the system reset logic. Refer
to Section 3.12 and schematic page AlphaPC64.38 for additional information.
Table 5–1 Power Supply dc Current Requirements (275 MHz)
Voltage Current
+5 V dc 10 A (maximum)
+3.3 V dc 10 A (maximum)
–5 V dc 0 A
+12 V dc 1 A (maximum)
–12 V dc 0.1 A (maximum)
Caution: Fan Sensor Required
The 21064A cooling fan must have a built-in sensor that drives a signal
if the airflow stops. The sensor is connected to J14.
When airflow is interrupted, the sensor signal fan_conn_l is asserted
causing the signal cpu_dcok to be asserted to the 21064A. This
protects the 21064A under fan-failure conditions because the 21064A
dissipates less heat when cpu_dcok is asserted.
Board Requirements and Parameters 5–1