Difference between 8-bit and 16-bit Microprocessor
8-bit v 16-bit Microprocessor
Before illustrating you the difference between 8-bit and 16-bit
microprocessor, Let me illustrate you the what actually this “8-bit” or
“16-bit mean”. An 8-bit CPU and ALU
architectures
are those that are based on registers, address buses, or data buses of
that size. 8-bit is also a term given to a generation of microcomputers
in which 8-bit microprocessors were the norm and for 16-bit it is the
vice-versa.
Lets know some interesting concept which leads us to know the difference between 8-bit ad 16-bit Microprocessor.
What is the difference between 8-bit and 16-bit Microprocessor ?
In June of 1978, Intel introduced the revolutionary new processor
called the 8086. It was one of the first 16-bit processor chips on the
market, at that time most of the all other processors had 8-bit design
architecture.
Intel 8086 Characteristics
| 3 um process |
| 29k transistors |
| 5-10 MHz |
| 16-bit word size |
| 16-bit external-internal bus size |
| 40-pin DIP package |
The 8086 had 16-bit internal registers and people started running new
softwares using 16-bit instructions. It has an 16- bit external
data bus, which means it could transfer data to memory
16 bits at a time.
And the
address bus was 20
bits wide, which means that the 8086 can address a full 1MB (2^20) of
memory. This made a stark contrast to most other chips of that time that
which had 8-bit internal registers, an 8-bit external data bus, and a 16-bit address bus allowing a maximum of only 64KB of RAM (2^16).
Unfortunately, most of the personal
computer world at that time was using 8-bit processors, which ran 8-bit Control Instructions for
operating systems and software. And the board and circuit
designs at that time were mostly 8-bit as well. Building a full 16-bit microprocessor and memory system would be very costly.
The cost was very high as the 8086 needed a 16-bit data bus rather than a
less expensive 8-bit bus. As all the systems available at that time
were 8-bit, and sales were also very low as of the 8086 indicated and
this made Intel to think that people weren’t willing to pay for the
extra performance of the full 16-bit design.
As a result, Intel introduced a new kind of crippled version of the
8086, called the 8088. The 8088 essentially deleted 8 of the 16 bits on the data bus, making the 8088 an 8-bit chip as far as
data input and output were concerned. Anyways as it retained the full 16-bit internal registers and the 20-bit address bus, the 8088 ran 16-bit software and was capable of addressing a full 1MB of RAM.
So the main difference is speed that is the frequency at which the instructions per cycle are executed
The following two are the microprocessors which are introduced by Intel which led to the evolution of 16-bit microprocessor
First Intel processor aftr 4004 series
Intel 8008 Characteristics
| 10 um process |
| 3500 transistors |
| 500 – 800 kHz |
| Do Memory Retention exercises |
| 8-bit word size |
| 18-pin DIP package |
Intel 8080 Characteristics
| 6 um process |
| 4500 transistors |
| 2 MHz |
| 8-bit word size |
| 40-pin DIP package |
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