Re: Microcontroller ... which one ??

From: ~~ VerilogMan ~~ (Zoroxeus_at_yahoo.com)
Date: 11/26/04 

Date: Fri, 26 Nov 2004 11:44:14 -0500

"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:SKydnUHthNBO0TrcRVn-2w@comcast.com...
>
>>
>> Thanks, but I don't really know RISC ... : |
>
> That's sort of nonsensical, don't you think?
> RISC is not a language.
> RISC is a marketing term, trying to make an advantage out of limited
> instruction space.
>
> Ex: The PIC is "risc", and the AVR is considered "CISC".
> The Pic should be faster right?
>
> At the same clock, the PIC takes four cycles to do anything, while most
> instructions on the AVR are one cycle. The PIC clocks a bit faster than
> the AVR, but nowhere near enough to make it up.
> Barely 2x, and they'd need at least 4X.
>
> Since the PIC has less instructions, a given function requires more
> instructions to get done. Also, the PIC has a single working register,
> where the AVR has 32, though the lower 16 are slightly limited. Where
> the AVR can store many critical things in registers, and modify/test them
> in one cycle, the PIC needs to load them into the W register (four cycles)
> test (four cycles) then save them back if it was a modify, for another
> four cycles.
>
> So it would seem that the overwhelming advantage is to the "CISC" machine.
>
> Remember, the limit case of RISC is a processor that has one "NOP"
> instruction, but executes it infinitely fast.

Hey thanks for the reminder,
I did not pay attention. I thought it was "another architecture" using less
and different instructions.
I guess CISC is way better for me anyways. !

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