System Overview
Overview
The KA49 CPU module combines with either the 4-MB or 16-MB
(or both) SIM modules to form the CPU/memory subsystem for
the VAXstation 4000 Model 90 product. The VAXstation 4000
Model 90 system is housed in a BA46 enclosure. The subsystem
uses the SCSI-1 bus to communicate with mass storage devices,
and transceiver cable (Thickwire or ThinWire connector) to
connect with an Ethernet network. A 16-bit programmed I/O port
connection is available to attach synchronous communications
or other options. An optional bus adapter can be connected to
the module using one of the 32-bit CDAL buses. Four serial
lines are supported for a keyboard, pointing device, printer,
and asynchronous communication. Audio input and output is
supported through the sound generator interface. The KA49 CPU
module supports low cost graphics using the LCSPX module or
high performance graphics using the SPXg/gt modules.
Main Memory
The KA49 CPU module can support up to eight memory SIM
modules to provide main memory configurations of 16, 32, 64, 80,
or 128 MB.
Cache Memory
The module uses multiple levels of cache memory to maximize
performance. The NVAX CPU contains a 2-KB virtual instruction
cache (VIC) and an 8-KB write-through primary cache (Pcache).
The KA49 module contains an on board 256-KB backup write
secondary cache (Bcache).
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