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Another popular microprocessor chip is the Motorola 68000 chip, used in the
Apple's Macintosh PCs. It is a 16/32-bit chip because it uses an internal data path
of 32 bits and an external data path of 16 bits. So all operations to and from
storage are done 16 bits (2 bytes) at a time, and data are processed 32 bits at a time
internally. Thus the 68000 is more powerful than the 8088 or 8086. The address
bus of 68000 chip has 24 lines, allowing a primary storage capacity of up to 16
Megabytes (224= 16,777,216 bytes).
Next came the more advanced Intel chips called 80286, 80386 and 80486. The
80286 chip was about six times faster than the 8086 chip and could support a
primary storage capacity of up to 16 Megabytes. It was used with the IBM
Personal System/2 (PS/2) models of PCs. It was soon superceded by the more
advanced Intel 80386 and 80486 chips, which were 32/32-bit chips. Other popular
32/32-bit chips were Motorola 68020 and 68030, used in some models of Apple's
Successors to the Intel's 80486 chip fall in the Pentium family of microprocessor
chips - Pentium Processor, Pentium Processor with MMX Technology, Pentium II
Processor, and Pentium III Processor. All these are 32/64-bit chips. That is, they
use an internal data path of 32 bits and an external data path of 64 bits. So all
operations to and from storage are done 64 bits (8 bytes) at a time, and data are
processed 32 bits at a time internally. Thus these chips are more powerful than the
80286, 80386, 80486, 68020, or 68030 chips. Most of the current days PCs are
built using the microprocessor chips of the Pentium family.
In addition to wider external data path, the microprocessor chips of the Pentium
family are also designed to have better clock speed so that they can execute more
instructions in a given unit of time than the earlier microprocessor chips. There are
two cycles that occur during the processing of each program instruction. These
instruction and execution cycles are synchronized by a specific number of electric
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This document was uploaded on 04/07/2014.
- Spring '14