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Subject: Re: data structure size on Pentium 1/2/3

Author: Bo Persson

Date: 13:06:50 04/18/00

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On April 18, 2000 at 14:27:52, Andrew Dados wrote:

>On April 18, 2000 at 12:48:28, Tom Kerrigan wrote:
>
>>On April 18, 2000 at 12:45:36, John Coffey wrote:
>>
>>>I am writting a data structure that I have to copy with every new node.  I was
>>>planning on using 16 bytes, but could maybe get it down to 8  using short
>>>integers.  I am wondering if short integers (16 bits) can be accessed any faster
>>>than 32 bit integers or if they are actually slower.  Also will the difference
>>
>>They're actually slower.
>>
>
>I'll be picky: that depends on alignment - may be faster or slower or same...:)
>Technically mov ax,[data16] has same timing as mov eax,[data32].

Even pickier:
In a 32-bit environment (like Windows or Linux) each 16-bit operation will need
an operand-size-override prefix. This adds to the code size.

>>>between copying 8 bytes and 16 bytes per node make any difference in
>>>terms of my overall speed?
>>
>>I doubt it. That's just 2 extra instructions, moving data around in cache.
>>
>>-Tom

Bo Persson
bop@malmo.mail.telia.com




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