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