Re: Looking for an armhf install image
On Mon, Apr 3, 2023 at 8:03 AM Lennart Sorensen
<lsorense@csclub.uwaterloo.ca> wrote:
>
> On Sun, Apr 02, 2023 at 09:51:23PM -0400, Alan Corey wrote:
> > I know I can but it will be twice as slow, which is why I want armhf.
> > Under 64 bit both the data and pointers will be twice as big. With
> > unlimited memory that would be OK but a Pi CPU can only access 1 GB.
> > I've tried 64 bit.
>
> It's certainly a balance trade off. The pointers will be twice as large.
> The data will be whatever size the code asked for. Only in the case that
> the code asked to use a long will be be 32 bit in one case and 64 bit
> in the other case. Most code isn't that sloppy about their data types.
>
> In terms of actual code, apparently the A53 core runs 64 bit code about
> 20% faster than 32 bit code, so it comes down to whether you are doing
> execution heavy or data heavy work.
There's one exception to 64-bit speedups that I am aware of. On A-57's
in 64 bit mode, ASIMD (formerly NEON) shifts used to be awful slow. It
was measurable. I'm not sure if it is still the case. See, for
example, http://github.com/weidai11/cryptopp/issues/367 .
It is better to use the integer units instead of the SIMD unit for
shifts in 64-bit mode.
Jeff
Reply to: