The Natural Philosopher  writes:

> On 30/06/2019 00:32, A. Dumas wrote:
>> The work involved to maintain two concurrent releases (with a lot of
>> customisations) is their main reason apparently, yes, while the vast
>> majority of the install base (the Pis out there) isn't 64 bit compatible.
>> But their main software man also keeps saying: give me one good reason why
>> 64 bit is better than 32. See their blog on the new Buster release. Well,
>> it gets a bit embarrassing with lost optimisations when the current chip is
>> armv8, for crying out loud. He says it doesn't make a difference but I
>> wonder.
>
> Wasn't the drive to 64 bit more about accessing more RAM?

More address space. CPUs with only 32-bit logical addressing can still
access more than 4GB physical RAM, but each process is still stuck in
4GB (often less in practice). That’s a problem both for certain lagre
applications, and for security improvements like ASLR.

64-bit GPRs are handy for some applications but rarely essential.

For both Intel and ARM the 64-bit instruction sets double the number of
architectural GPRs. Particularly on Intel where the 32-bit situation is
pretty poor, that’s a big improvement for anyone writing in assembler.

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

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