6
Features of the AlphaPC 164 Motherboard
2.1 Power Requirements
The AlphaPC 164 motherboard has a total power dissipation of 116 W, excluding
any plug-in PCI and ISA devices. Table 3 lists the power requirement for each dc
supply voltage.
The power supply must supply a DCOK signal to the system reset logic.
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 motherboard connector J21. When the signal
is generated, it resets the system.
2.2 Environmental Requirements
The 21164 microprocessor is cooled by a small fan blowing directly into the chip’s
heat sink. The AlphaPC 164 motherboard is designed to run efficiently by using only
this fan. Additional fans may be necessary depending upon cabinetry and the
requirements of plug-in cards.
The AlphaPC 164 motherboard is specified to run within the environment listed in
Table 4.
1
Values indicated are for an AlphaPC 164 motherboard (64MB DRAM) excluding
adapter cards and disk drives.
Table 3 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 A
+12 V dc,
±
5%
1.0 A
–12 V dc,
±
5%
100.0 mA
