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What does one mean by saying an 8-bit microprocessor ?

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Hamidzia

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internal data bus width

Assalam O Alekum !

Kindly remove my confusion

What does one mean by saying an 8-bit microprocessor

Is it the data bus width?
Is it the address bus width?
Is it the internal bus width?

Kindly answer when u r 100 % confident about that.

Thankx
 

Re: Microprocessor

the 8 bits works internally at 8 bit data bus, but this not means that all registers internally are only 8 bit.
the 8 bits really work whit external data bus at 8 bit or more but whit more cycles.
 

Microprocessor

Means the ALU, Register, Mem and the BUS between them are 8 bits.
 

Re: Microprocessor

It means that the data path is 8 bits
 

Re: Microprocessor

Elton ..
I guess the data pathes may not all be 8-bit to call the processor an 8-bit processor .. some processors now adays have different internal data buses .. and to go away from the conflict .. let's consider the data port of the memory .. ( though the term memory is quite large ) , the base behind the word data-bus ...

am I right ?
 

Re: Microprocessor

:?

8 bit microprocessor means that it's ALU is of 8 bit and it
can do calculations on 8 bit binary number.genarally its
data bus is of 8 bit wide.its registers is 8bit wide(normally).
 

Re: Microprocessor

i agree with kirangv. at least i know that this is what ive read in books and ive heard the same from my teachers
 

Re: Microprocessor

well .. i have learnt so as well .. but when i come to design a microprocessor myself .. in a big firm .. i discovered that having a non-8bit register in an 8-bit microprocessor is something normal .. let's say in RISC processors and application specific processors specifically ..
for example .. i have designed an FFT/IFFT microprocessor with a data path unit called Butterfly .. ( of course not ordicary data path unit ) .. this unit used to use certain bigger registers thahhn the regular ALU register file ..!!

I know this is not the default in the book .. specially educational books .. where basics and infra-structure priciples to be taken .. but .. this is life :) .. u can do whatever u want in ur design :) .. just to solve ur problem :)
 

Re: Microprocessor

It has nothing to do with address width. A 16-bit processor can have 24 bit addressing but 16-bit ALU, Accumulator, Stack Pointer and Index.
 

Re: Microprocessor

I agree address bus size has nothing to do with processer bit size. But generally when we say that we have an 8-bit cpu then we mean that the data bus and the registers/Alu sidth is 32 bits. But again it can be diffrent in special purpose harware. So there is no exact rule or definition.
 

Re: Microprocessor

Hope you find this useful:
The term 8-bit means that the ALU (Arithmetic Logic Unit), the internal registers, and most of the instructions are designed to work with 8-bit binary words.

It's not related to the data bus. For example: The 8086, which is a 16-bit microprocessor has a 16-bit data bus; whereas it's address bus is 20-bit.

In short a microprocessor with a 8-bit ALU will be referred to as an 8-bit microprocessor.

Source of the above information:
Microprocessors and Interfacing, 2nd ED by Douglas V. Hall
 

Re: Microprocessor

All the processing power of the processor is 8 bits .....I mean the registers and Arithmatic logic unit can handle 8 bits at one time......

Outer data bus may be greater than 8 bits..........but main processing power is 8 bits.........
 

Re: Microprocessor

"The Electrical Engineering Handbook" (Richard Dorf, Editor) states the data path is what is referred to by a term such as 8-bit and would mean at least all of the following are 8-bits wide:

The data bus.
The ALU.
The memory registers.
Any internal RAM (but not common in 8-bit processors).

Therefore, "8-bit" does include the data bus width.

"8-bit" says nothing about the address width. For example in a Z-80, an 8-bit processor, the address width is 16 bits.

The generic term bus (internal bus in the original post?) includes both the data and address bus and is therefore the sum of the two widths.
 

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