Re: amd64 running on Intel Celeron and Pentium? (was: [SECURITY] [DSA 5113-1] firefox-esr security update)

On Fri, Apr 15, 2022 at 10:12:23AM +0200, Elmar Stellnberger wrote:
> On 14.04.22 15:45, Levis Yarema wrote:
> > Is there in deed any reason to prefer amd64 over i586 if you have the
> > choice and a machine with 2GB RAM or less, apart from perhaps long term
> > support?
> > 
> 
>   Depends on the application. Encryption and decryption
> requiring the simulation of very larger integers shall be faster
> when being based on 64bit integers. However these are rather
> special purposes.
>   CPU and memory intense applications like the SAT-solver I am
> developing on the other hand will be faster on i386 since a
> memory reference/ pointer only requires 4 byte instead of 8
> byte. Smaller size will yield less memory access cycles and more
> cache hits and that can make an application considerably faster.
> It is the cache that is effectively more important than the
> register layout. Some SAT-solvers like f.i. the DNNF-c2d are
> only available for Linux/i386, not for amd64.
>   Concerning general purpose applications normal integers keep
> to be 32bit even on amd64. Note the sizeof(int). This is also
> for the rationale described above. x86_32 programs can even be
> smaller on disk and in memory. I personally don´t think that
> there is much reason to use amd64 with 2GB ram or less, except
> for bigint calculations.
>   Note however that with a 64bit kernel you can execute programs
> in a 64bit and 32bit chroot while this is impossible with a
> 32bit kernel. This is a reason why many people boot with a 64bit
> kernel but use a 32bit installation. As for certain CPU and
> memory intense programs you can run them as i386 binary even on
> an x86_64 root given that i386 system libararies are installed
> which is possible with dpkg --add-architecture i386.
> 

And i you're runnin Lisp programs, you'll definitely want a 32-bit architecture, because Lisp fills memory with addresses.  But you can do that with add-architecture i286.

-- hendrik