Intel Embedded Intel486, Hardware Reference Manual

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EMBEDDED Intel486™ PROCESSOR HARDWARE REFERENCE MANUAL
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2.5.1 Embedded Personal Computers
In single-processor embedded systems, the processor interacts directly with I/O devices and
DRAM memory. Other bus masters such as a LAN coprocessor typically reside on the system
bus; conventional personal computer architecture puts most peripherals on separate plug-in
boards. Expansion is typically limited to memory boards and I/O boards. A standard I/O archi-
tecture such as MCA or EISA is used. System cost and size are very important.
Figure 2-5 shows
an example of an embedded personal computer or an embedded controller application.
Figure 2-5. Embedded Personal Computer and Embedded Controller Example
External cache is optional in such environments, particularly if system performance is not a crit-
ical parameter. Where an external cache is used, memory-access speeds improve only if the cache
is designed as a write-back system and memory access has zero to one wait states.
2.5.2 Embedded Controllers
Most embedded controllers perform real-time tasks. The performance of the Intel486 processor
and its compatibility with the extensive installed base of Intel386 processors are important factors
in its choice. Embedded controllers are usually implemented as stand-alone systems, with less ex-
Intel486™
Processor
Bus
Processor Bus
System Bus
Optional Local
Memory
Level-2 Cache
Local
Peripheral
Controller
Controller
Other
Peripheral
“Slow”
Memory