From quick googling - could this PC also named as "Acer Acros 325SE"? Looks similar, maybe this yields more results. See ebay.com/itm/314978735901 - there on one image you can see power adapter model and pin layout.

/edit - I'll add part of image here/

Here you go:

uname -p print the machine processor architecture name.

uname -m print the machine hardware name.

The arch command with no arguments, displays the machine's architecture type.

Ultimately I suspect this is the answer you want: https://stackoverflow.com/questions/12763296/os-x-arch-command-incorrect

For further confusion, run:

$arch
i386
$machine  
i486
$uname -m
x86_64
$uname -p
i386

If want compile the file as 32 bits, you can use:

ld -m elf_i386 -s -o file file.o