The head of the Intel family of microprocessors is the 8086, the first
widely used 16 bit microprocessor. Although they also created the 8 bit microprocessor,
their dominance in the PC industry's hardware and architecture became established
when IBM selected the 8088 for use in its first IBM PC. The 8088 is an offshoot
of 8086, and is also a 16 bit processor.
In addition to doubling the data bus width from 8 to 16, the 8086 also increased the number of address lines from 16 to 20, and thus, the amount of addressable memory increased to 1 MB. The 8088 which IBM used for its PC is essentially the same as the 8086, except that the bus is multiplexed down to 8 bits.
The next microprocessor, the 80186, is just an 8086 with several support functions built right in : clock generator, system controller, interrupt controller, direct memory access controller, and timer or counter. The 8086 also started using 8, 10, or 12.5 MHz clock rates. Despite this improvements, the chip was limited to embedded applications.
The 80286 which followed is a considerable improvement over the 8086.
It has 24 address lines which can access 16 MB of memory. It also has 2
modes of operation, the real and the protected mode. With the real mode,
it is compatible with softwares written for 8086. It can also switch to
the protected mode to access the entire 16 MB of memory and other advance
programming features. However, the memory management of this chip is quite
crude : in order to switch back to the real mode from protected mode,
the whole chip has to be reset. Thus, it is not suitable for running multi-tasking
softwares such as Windows.
The first 32
bit microprocessor of Intel is the 80386. Both the data and address bus are
32-bit. It has 3 modes, and unlike its predecessor, has efficient mode switching.
It also uses instruction pipelining (also known as scalar architecture), which
allows the CPU to start working on a new instruction before completing the
current one.
The 386 has 2 versions, the 386SX and the 386 SL. The SX has 16-bit external bus, and a 24-bit address bus. The SL is similar to SX, with additions of power-management circuitry and system functions for running a standard PC.
The 486 was introduced in 1989, and is a modest improvement over the 386. It includes on-chip cache, which is 4-way set associative, and a floating point unit. It also comes in either 3 or 5 volts, especially suited for portable computers.
It also has an SX version. In this case, 486SX has no floating point unit in its chip. Intel also made the 486 upgradeable. They released the 80486DX2/50 as the first upgradeable 486.
Intel was not able to patent a number, that's why they named their
next chip as Pentium, instead of 586. It is largely the same as the 32 bit
486 but has a 64 bit data bus. There is also additional instructions and
on-board math coprocessor is provided.
Subsequent developments of the Pentium can be tracked at intel's homesite.
Below is the table of Intel chips. The development of the chips can easily be surmised from the tabulated data.
|
Processor |
4004 |
8080 |
8086 |
8088 |
80286 |
80386 |
|
Introduced |
Nov 1971 |
April 1974 |
June 1978 |
June 1979 |
Feb 1982 |
October 1985 |
|
Launch price |
$45 |
$360 |
$360 |
$360 |
$360 |
$299 |
|
Architecture |
4-bit |
8-bit |
16-bit |
16-bit (8-bit externally) |
16-bit |
32-bit |
|
Addressable memory |
640 bytes |
64KB |
1 MB |
1 MB |
16 MB |
4 GB |
|
Transistors |
2,300 |
6,000 |
29,000 |
29,000 |
134,000 |
275,000 |
|
Initial clock speed |
108KHz |
2MHz |
5 MHz |
5 mHz |
8 MHz |
16 MHz |
|
Initial MIPS |
0.06 |
0.64 |
0.33 |
0.33 |
1.2 |
5 |
|
comment |
The world's first microprocessor |
Ten times performance of 8008 |
The first 16-bit processor |
Used in the IBM PC |
Used in the IBM PC/AT |
Supplied in two variants, 386DX with full 32-bit external bus, and 386SX with 16-bit external bus |
|
Processor |
80486 |
Pentium |
Pentium Pro |
|
Introduced |
April 1989 |
March 1993 |
Nov 1995 |
|
Launch price |
$950 |
$878 |
$974 |
|
Architecture |
32-bit |
32-bit (64-bit external bus) |
32-bit (64-bit external bus) |
|
Addressable memory |
4 GB |
4 GB |
4 GB |
|
Transistors |
1.2 million |
3.1 million |
5.5 million + L2 cache |
|
Initial clock speed |
25 MHz |
60MHz |
150MHz |
|
Initial MIPS |
20 |
300 |
|
|
comment |
Supplied in two variants, 486DX with full on-chip floating point instructions, and 486SX with no on-chip maths functionality. |
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