[Techtalk] i386 or i686?

Alvin Goats agoats at compuserve.com
Thu Oct 30 22:53:11 EST 2003

> I had an issue some time back where a system, installed on a celeron box,
> was transferred to an AMD box (ie. the HD was moved) and it wouldn't run.
> Once I removed the i686 kernel and glibc (which is all that is i686 in
> RH7.2) replaced them with i386 versions, the move was fine.

Once everyone got past the i486 stage, they started forking pretty
heavily. Cyrix went one way and eventually failed after the i586/Pentium
stage. AMD continued on for a while chasing Intel, but they started
developing different processor lines which don't always perform in the
same processor class.

AMD has some chips in the i586 class that won't run as i686, but their
performance is the same as an i686 processor. This might be part of the
problem you experienced: a processor of sub-i686 design that can perform
at i686 levels and hence the i686 software wouldn't run.

If you remember way back when, there were some 486 chips that ouuld
outperform the early pentiums (486DX-100 vs. Pentium 75). The 486 ran
faster than the pentium, but the OS for a Pentium would not run on the

If you are going to do anything with an AMD, I'd contact AMD and get
details about what processor type it is for Linux optimization:
www.amd.com. Their current processors run at slower clock speeds, but
due to architecture design will run head to head with processors that
may be 2x faster (like the 2200+, the plus indicates a slower clocked
processor that performs at about a 2200 MHz Intel chip). They gave a
presentation to our local Unix Users Group and talked about some of
these issues.


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