8 bits..

[Mike Prince]

On Mon, 19 Dec 1994, Dr. J. Van Sckalkwyk (external) wrote:

> About the 8 / 16 / 32 bit thing!
> One question is, is the added efficiency of allowing
> 8 bit and/or 16 bit "items" worth the added complexity?
> My gut feeling is "NO", especially as things seem to
> be getting more and more "32 bit streamlined" as we
> "progress"! We may find that adding in 8 and 16 bit
> "items" will actually _decrease_ our efficiency d/t
> the added overheads of more testing for data types, etc
> especially on the machines where we want optimum
> performance ie. 32 bit machines.

I'm guessing the total overhead in using 8,16's and floats in addition to 
32's will increase the essential system code (core, kernel, whatever by 
about 5K).  Application code will at least remain the same size, but will 
probably get smaller (using 16's instead of 32's).

The code I'm writing is not that dependent on data size, so it would be 
easy to try both out (32 only or mixed) and see which fits us best.  At 
this time though, my gut feeling is to stick with multiple "base" types.

> ((One question - a dream perhaps - is "how many gates
> (etc) could they have cut out of the 386 (or whatever)
> if they only dealt in 32 bit instructions?" - Just a
> RISCish thought))!

That's a little pipe dream of my own.  I'd like to design an OS/LLL that 
would allow a sly microprocessor house to make a cpu that just includes 
what's needed, lowering costs, increasing speed, etc.  The MuP21 is just 
one such example, though not focused enough in OUR direction.

> In terms of data transfer, I do not see the 32 bit coding
> as a big problem, because if we are transferring "ASCII"
> where "A" is represented as 00000041 rather than 41,
> it is easy (for example) to establish a convention where we
> signal that <the following is all "32 bit pseudo-ASCII"
> packed 4 characters per 32 bits> or "merely" apply
> compression to reduce volume. I do not see either as 
> involving a massive overhead.

I'm trying to stay away from bit twidling "too much", for instance 
putting 3 characters in a 32 and somehow saying extract just three, etc.

> Bye, JVS<

Thanks for the feedback!

Mike