druck  writes:
> On 02/07/2019 09:10, The Natural Philosopher wrote:
>> Umm. Can a 32 bit OS run 64 bit programs?
>
> No that isn't possible as a 32 bit OS can't set up the required 64 bit
> configuration. But a 64 bit OS can run both 64 bit and 32 bit
> programs.
>
> There is also a mode called ILP32, which uses the 64 bit ARMv8
> instruction set, but 32 bit longs and pointers. So you get the
> benefits of the improved instruction set (more registers, better
> branch prediction), but avoid the disadvantage of increased cache when
> dealing with 64 bit values.
>
> The only drawback is you need a complete set of ILP32 compiled
> userland libraries, nearly doubling the size of your OS image (or
> adding another 50% if you've already got a true 32 bit userland).

Less room for ASLR would be the other drawback.

There’s a similar thing in the Intel Linux world, call X32. I’ve never
heard of anyone using it in anger...

--
https://www.greenend.org.uk/rjk/

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