why not odd number microcontrollers

[electronicsLearner77]

I know we have 8 bit, 16 bit and 32 bit controllers. I know 9 bit micro controllers or all different size of micro controllers are not possible and wanted to know the exact reason why it is not possible?

 

[BobK]

No it is not impossible. It takes 8 bits to store an ASCII character, so most architectures use a multiple of 8 bits. One could design a 9-bit processor, but why?

Bob

 

[Minder]

I cut my teeth on the PDP8 which was 12 data bits.

M.

 

[electronicsLearner77]

Thanks for the reply. Mainly I was relating this with the data types like char (8 bits), int (16 bits) etc. Why cannot l have variable data type that is any number of bits I want I can access. I know it is stupid question but please tell me the reason.

 

[Minder]

I think it is a question of practicality when designing the architecture of the system, if every data word handled was unknown length from one to the next it would be difficult to design a system that could handle this, and just complicate things unnecessarily.
M..
,

 

[AnalogKid]

Thanks for the reply. Mainly I was relating this with the data types like char (8 bits), int (16 bits) etc. Why cannot l have variable data type that is any number of bits I want I can access. I know it is stupid question but please tell me the reason.

Standardization and conformity. A small number of data path widths limit some options, but the cost drops dramatically when millions are made. Using 16-bit wide RAM data is wasteful for 12-bit values, but cost 1/1000th the price of a true 12-bit wide data system.

Honeywell mainframes has 36 bit words.

ak