Hardware Reference
In-Depth Information
Motorola engineers who had worked on Motorola's first processor, the 6800, designed this chip. The
6502 was an 8-bit processor like the 8080, but it sold for around $25, whereas the 8080 cost about
$300 when it was introduced. The price appealed to Steve Wozniak, who placed the chip in his
Apple I and Apple II/II+ designs. The chip was also used in systems by Commodore and other system
manufacturers. The 6502 and its successors were used in game consoles, including the original
Nintendo Entertainment System (NES), among others. Motorola went on to create the 68000 series,
which became the basis for the original line of Apple Macintosh computers. The second-generation
Macs used the PowerPC chip, also by Motorola and a successor to the 68000 series. Of course, the
current Macs have adopted PC architecture, using the same processors, chipsets, and other
components as PCs.
In the early 1980s, I had a system containing both a MOS Technologies 6502 and a Zilog Z80. It was
a 1MHz (yes, that's one megahertz!) 6502-based Apple II+system with a Microsoft Softcard (Z80
card) plugged into one of the slots. The Softcard contained a 2MHz Z80 processor, which enabled me
to run both Apple and CP/M software on the system.
All these previous chips set the stage for the first PC processors. Intel introduced the 8086 in June
1978. The 8086 chip brought with it the original x86 instruction set that is still present in current x86-
compatible chips such as the Core i Series and AMD FX. However, it was a reduced-feature version
of the 8086, the Intel 8088, that became the processor used by the first IBM PC.
To learn more about the 8086 and 8088, see the section, “
P1 (086) Processors
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PC Processor Evolution
Since the first PC came out in 1981, PC processor evolution has concentrated on four main areas:
• Increasing the transistor count and density
• Increasing the clock cycling speeds
• Increasing the size of internal registers (bits)
• Increasing the number of cores in a single chip
Intel introduced the 286 chip in 1982. With 134,000 transistors, it provided about three times the
performance of other 16-bit processors of the time. Featuring on-chip memory management, the 286
also offered software compatibility with its predecessors. This revolutionary chip was first used in
IBM's benchmark PC-AT, the system upon which all modern PCs are based.
In 1985 came the Intel 386 processor. With a new 32-bit architecture and 275,000 transistors, the
chip could perform more than five million instructions per second (MIPS). Compaq's Deskpro 386
was the first PC based on the new microprocessor.
Next out of the gate was the Intel 486 processor in 1989. The 486 had 1.2 million transistors and the
first built-in math coprocessor. It was some 50 times faster than the original 4004, equaling the
performance of some mainframe computers.
Then, in 1993, Intel introduced the first P5 family (586) processor, called the Pentium, setting new
performance standards with several times the performance of the previous 486 processor. The
Pentium processor used 3.1 million transistors to perform up to 90 MIPS—now up to about 1,500
times the speed of the original 4004.
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