On Mon, 15 Jan 2018 20:54:58 +0100
Stefan Enzinger  wrote:

> On 2018-01-15 19:30, Ahem A Rivet's Shot wrote:
> > On Mon, 15 Jan 2018 17:56:14 +0000 (UTC)
> > Kiwi User  wrote:
> >
> >> Assuming that RPi binaries for the same set of programs are about the
> >> same size as as the X-64 ones, that implies that very much less file
> >
> >  ARM binaries are quite a bit more compact than X86-64 binaries
> > which is why ARM hardware manages with less memory than PC hardware.
>
>
> I always have a hard time accepting that.
> ARM is RISC, x86 CISC. I would assume one needs more RISC instructions
> to achieve the same CISC instructions. So RISC binaries would be bigger.
> But I guess single x86 instructions are bigger then ARM instructions.

 Yes ARM instructions are all 32 bit, apart from the 16  bit thumb
instruction set supported on most ARMs. Most ARM instructions are
conditional which eliminates some branching and there's a barrel shifter
which can be applied as part of just about any instruction (so something
like a shift and add is a single instruction executed in one cycle).

 The combination is very effective at producing compact efficient
code (especially when thumb is used).

> And large parts of code are not even using the specialized subset of
> CISC...

 That was always the weak point of CISC, do the extra instructions
get enough use to justify the silicon.

> always assuming same pointer size (32 bit vs 64 bit)

 Indeed.

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