of the other components. So replacing an 8086 processor in an old
PC by an 80386 processor does not mean that the PC will be able to
run at 20 or
25
MHz.
The original IBM PC with its 8086 chip supported a clock speed
of 4.77 MHz. To execute the average instruction required about 15
clock cycles, so its processing speed was 0.3
MIPS.
The latest PCs
using the 80486 chip have clock speeds of 30 or 35 MHz and execute
an instruction in just over 2 clock cycles, giving a processing speed
of around
15
MIPS.
The i860 RISC chip has a clock speed of around
40 MHz and executes about 1 instruction per clock cycle, giving a
processing speed o
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