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Systems with multiple I/O channels frequently use dual-ported memory to link several identical
I/O devices to the local bus, as in
and flexibility improve because bus traffic is partitioned away from the i960 Jx processor's local
bus. An example of such a system might be a network hub.
i960 Jx
Processor
Figure 14-19. Generalized 80960Jx System with 80960 Local Bus
A more elaborate system would connect the 80960Jx's bus to a backplane through bus interface
logic as shown in
Figure
14-20. The backplane bus (or system bus) connects to multiple high
performance I/O devices (often with DMA) and large buffer memory for caching packets of data
from disk drives or LANs. Backplane buses can connect to other microprocessor local buses, too,
creating a loosely coupled multiprocessor system for resource sharing.
Figure 14-20. Generalized 80960Jx System with 80960 Local Bus and Backplane Bus
Figure
14-19. These systems are more complex, but performance
Local
Base
Memory
I/O
80960 Local Bus
i960 Jx
Local
Memory
Processor
80960 Local Bus
Cache
High-Perf
Bus
Memory
Interface
Backplane Bus
EXTERNAL BUS
Dual Port
High-Perf
Memory
I/O
Base
I/O
I/O
14
14-35
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