[OM Cooker] One users reasons for using i586 on 64 bit hardware.

Colin Close itchka at compuserve.com
Mon Dec 26 08:58:43 EST 2016


The X32_ABI looks interesting and I think that is what D21 was referring to at the end of his post.
It does look like this would offer improved performance for 32bit apps running on 64bit boxes.
What is more the SSE instructions become available.
I wonder what is involved in creating such a release? 
Best,
Colin

On Monday, 26 December 2016 07:53:05 GMT Paulo César Pereira de Andrade wrote:
> 2016-12-25 16:33 GMT-05:00 His Shadow <shadowpilot34 at gmail.com>:
> > I thought that only addresses doubled, not the instruction opcodes.
> 
>   This is mostly right. Instructions that use 64 bit operands, or
> registers with absolute value larger than 7 also need a prefix
> https://en.wikipedia.org/wiki/VEX_prefix#REX
> 
>   Running in 32 bit mode also uses only 8 from the 16 registers.
> 
>   It is possible to have a 32 bit distro enabled, just that some
> directories will conflict, e.g. there is no /bin32 or /bin64.
> 
>   About the upper 32 bits, some instructions do not touch the upper
> 32 bit, some zero fill and other sign fill the result, and most have
> some encoding to tell if using 32 or 64 input operands.
> 
>   Some distros have a x32 version:
> https://en.wikipedia.org/wiki/X32_ABI
> that uses 32 bit pointers.
> 
> Thanks,
> Paulo
> 
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