Processor requirements

[Jonathan S. Shapiro]

I'm currently settling the cross-build tools for Coyotos, and I'ld like
some input on something.

In EROS, I decided early *not* to support the i386. EROS required i486
or better. This is because the i386 does not honor the write-protect bit
in supervisor mode, and we need this for efficiency in the IPC
implementation.

Given that it is now 2005, does anybody see a need today to support
processors earlier than i686 in desktop PCs?

The specific features I am looking for are the "page size
extensions" (4M pages) and the per-page global bit. I *think* that both
of these were actually present in the appendix H extensions for the
Pentium, but I'm not certain about PSE. I have appendix H in a box
somewhere, but I'm damned if I can locate it at the moment.

I am aware that embedded processors like Geode don't all do PSE. We need
to support those, but the question I'm trying to ask right now has to do
with the minimum level of PC motherboard that the Hurd group wants to
support.

shap