Microprocessor
The heart
of
the system board
is
the Intel 8088 Microprocessor.
This
is
an
8-bit external-bus version of Intel's 16-bit 8086
Microprocessor, and
is
software-compatible with the 8086. Thus,
the 8088 supports 16-bit operations, including multiply and
divide, and 20 bits of addressing (1M byte of storage).
It
also
operates in maximum mode, so a coprocessor can be added as a
feature. The microprocessor operates
at
4.77MHz. This
frequency
is
derived from a 14.31818MHz crystal, the frequency
of
which is divided by 3 for the microprocessor clock, and divided
by
4 to obtain the 3.58MHz color-burst signal required for color
televisions.
At
the 4.77MHz clock rate, the 8088 bus cycles are four clocks of
210 nanoseconds (ns) each,
or
840ns total. Some
I/O
cycles take
five 210ns clocks
or
1.05 microseconds
(J-ts).
1-4 System
Board
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