Specifications

Power Hawk 620/640 Hardware Environmen
t
7-5
Another bus on the Power Hawk systems is the local ISA bus, which is used to
communicate with the serial and parallel ports, NVRAM, and the Real-time Clock
Module. There is no provision for customers to add devices to the ISA bus.
VMEbus support is provided by a Tundra Universe chip. This chip interfaces between the
PCI bus and the industry-standard VMEbus. The VMEbus provides A32 addressing and
D64 data transfers. Any third-party controller that can be strapped to addresses
appropriate to the Power Hawk VMEbus can be connected to it.
Timers 7
Timers are provided by three sources on the Power Hawk. The ISA Bridge chip, a
Winbond W83C553F, contains an interruptible timer. This is used to provide the 60 Hz
clock interrupt. The Z8536 multipurpose chip connected to the 82378 contains three 16-
bit timers used for real-time clocks. In addition, the Raven MPIC Interrupt Controller
provides four 32-bit timers for additional real-time clocks.
Interrupts 7
Interrupt control is provided by several devices. The main control center is the Raven
Multiprocessor Interrupt Controller (MPIC) chip located in the Processor-PCI bus bridge.
This controller implements the pseudo-standard MPIC capability defined for CHRP-
compliant systems. It accepts and routes interrupts from the W83C553F ISA Bridge
controller and the Tundra Universe VME Bridge Controller along with internally
generated interrupts. Individual priority control is provided by an Interrupt Priority
Register in the MPIC and by enabling/disabling each of the 16 ISA levels in the ISA
Bridge Controller.
Data Types 7
The Power Hawk supports the following data types:
• Byte (8 bits)
• Half-Word (16 bits)
• Word (32 bits)
• Doubleword (64 bits)
The Power Hawk 620/640 computer systems are 64-bit machines, but in order to remain
compatible with other industry standard systems, the use of the nomenclature word for
sixteen bits and longword for 32 bits has been retained.