Re: Any more graceful way to saturate adds?

On the real 8088 IBM PC the cycle count is total bytes in the
instruction and data being referenced times the wait states.  The PC
had so many waits on memory access that only a few instructions such
as multiply and divide would take more CPU cycles than the fetch.

On Fri, 18 Apr 2008 02:31:30 -0700 (PDT), Danjel McGougan
<spamtrap@[EMAIL PROTECTED]
> wrote:

>On 17 Apr, 20:14, Terje Mathisen  <spamt...@[EMAIL PROTECTED]
> wrote:
>> pete wrote:
>> >> Was Terje's solution:
>>
>> >>   add dl,al     ; Carry set if it overflows!
>> >>   sbb al,al     ; AL = 0xff if overflow
>> >>   or dl,al      ; Turns any overflow into 0xff
>>
>> >> ...the right one?  I see overflow handling but not underflow...
>>
>[...]
>>
>> Anyway, unless clamping is very common, it is hard to beat the branch
>> predictors!
>>
>
>I don't think the 808x CPU has a branch predictor. I guess one could
>just add up the cycles used for each instruction on such an old CPU
>and come up with the best performing code for various statistics of
>the data. It should be pretty much deterministic (does it even use
>cache memory?).
>
>BR,
>Danjel McGougan