slackware 10.1 lowest requirements are

# 486 processor
# 16MB RAM (32MB suggested)
# 100-500 megabytes of hard disk space for a minimal and around 3.5GB for full install
# 3.5" floppy drive

there is included with slackware 10.1 lowmem.i
according to "creating a bootdisk" page lowmen.i accompanies this:

This is a really stripped-down Linux kernel which might be useful for installing on IDE systems with a low amount of RAM (less than 8MB). It's also the only Slackware kernel that supports old 386 machines. If bare.i runs into problems, you might try this. NOTE: On systems with extremely low memory (4MB), ZipSlack plus the fourmeg.zip add-on (found in the zipslack directory) may boot and run even in cases where lowmem.i doesn't. If you have to use lowmem.i to install, you'll then probably have to compile a custom kernel with the minimal additional features that your machine requires.


I thought gcc changed recently to only compile 486 upwords

What should i take as the bare minimum? 486 or 386

486, like you say, Slackware Linux is compiled with -march=i486. Besides that IIRC compiling glibc for i386 breaks the C++ binary compatibility with other distributions.