UNIX Performance Penalties

[Conor P. Cahill]

In article <I_S6Q:C at xds13.ferranti.com> peter at ficc.ferranti.com (Peter da Silva) writes:
>In article <2202 at sixhub.UUCP> davidsen at sixhub.UUCP (bill davidsen) writes:
>>   If your application is compiled for 32 bit unix using a good
>> compiler, and uses 32 bit int data, you will get about 2:1 (I didn't
>> believe it until I measured it either).
>
>I'm surprised it's so small. The speed difference for pure-CPU on
>a 286 between small and large model (accessing 20000-int-long array
>at effectively random versus accessing a 40000-int-long array) is on
>the order of 11:1!

Thats because you guys are talking about apples and oranges.  The performance
difference between small and large models deals with the additional overhead
of computing addresses using the segment descriptor (including maintaining 
the segment descriptors for every far address).  The benefits of using a 
32 bit compiler on a 32 bit machine deals with using a natural format 
integer (as far as the processor is concerned) vs having to fake it.


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Conor P. Cahill            (703)430-9247        Virtual Technologies, Inc.,
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