On Fri, Jun 29, 2018 at 10:20:50AM +0100, Luke Kenneth Casson Leighton wrote:
>  in addition, arm64 is usually speculative OoO (Cavium ThunderX V1
> being a notable exception) which means it's vulnerable to spectre and
> meltdown attacks, whereas 32-bit ARM is exclusively in-order.  if you
> want to GUARANTEE that you've got spectre-immune hardware you need
> either any 32-bit system (where even Cortex A7 has virtualisattion) or
> if 64-bit is absolutely required use Cortex A53.

The Cortex A8, A7 and A5 are in order.  The A9, A15, A17 etc are out of
order execution.  So any 32 bit arm worth using is pretty much always
out of order execution.

For 64 bit, I think the A35 and A53 are in order while the A57, A72 etc
are out of order.

Of course non Cortex designs vary (I think Marvel's JP4 core was out of
order execution for example).

After all, in general in order execution equals awful performance.

Len Sorensen

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