CPU System Overview
2.1 CPU Module Features
2.1 CPU Module Features
The KA681/KA691/KA692/KA694 CPUs are quad-height VAX processor
modules that use the Q22–bus and DSSI bus. The CPUs are used in the
following systems:
System
CPU
VAX 4000 Model 500A
KA681
VAX 4000 Model 505A/600A
KA691
VAX 4000 Model 700A
KA692
VAX 4000 Model 705A
KA694
The CPU module is designed for use in high-speed, real-time applications
and for multiuser, multitasking environments. The KA681/KA691/KA692
/KA694 employ multiple levels of cache memory to maximize performance. See
Figure 2–1 for a view of the major chips, LEDs, and connectors. Table 2–1
describes the CPU module components. See Figure 2–2 and Figure 2–3 for
block diagrams of the major functions.
The CPU module and MS690 memory modules combine to form the CPU
/memory subsystem that uses DSSI buses to communicate with mass storage
devices, the Q22–bus to communicate with I/O devices, and the Ethernet to
communicate across the network.
The CPU module and optional DSSI daughter board combine to expand the
DSSI buses’ capability to four ports. See Figure 2–5 for a view of the major
chips and connectors.
The CPU module is configured as an arbiter CPU on the Q22–bus, where it
arbitrates bus mastership and fields any on-board interrupt requests.
2–2 CPU System Overview
