Date: Fri, 7 Oct 1994 18:24:20 -0700 (PDT)
From: "Frederick W. Reimer" <fwreimer AT crl DOT com>
Subject: Re: 16/32 (was: djgpp and the 386SX)
To: terra AT diku DOT dk
Cc: FIXER AT FAXCSL DOT DCRT DOT NIH DOT GOV, djgpp AT sun DOT soe DOT clarkson DOT edu

On Thu, 6 Oct 1994 terra AT diku DOT dk wrote:

>    Date: Wed, 5 Oct 1994 18:38:59 -0400 (EDT)
>    From: Chris Tate <FIXER AT FAXCSL DOT DCRT DOT NIH DOT GOV>
> 
> [...]
> 
>    I believe that 16-bit integer operations are faster on the I486 and before;
>    I don't know about the Pentium.  Anybody know for sure?
> 
> (meaning faster than 32-bit operations)
> 
> There is no execution time difference between 16-bit operations and
> 32-bit operations for i[34]86.
> 
> However, if you are in a 32-bit segment (djgpp world) then 16-bit
> operation have to be tagged with a prefix which make them slower.
> In a 16-bit segment (dos world) it is the other way round.
> 
> Furthermore, the execution times for multiplication and division
> depend and the actual values used, but not on the size of the
> registers used.
> 
> Morten
> 

I'll have to assume that you also have the 386+ programmer's reference 
manual from Intel -- or at least have the instruction timings from some 
(supposedly) 32-bit compiler?  Thanks for setting the facts striaght!

Fred Reimer

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