Kernel panic with ACPI enabled

[Warner Losh]

> It seems to me that eisa was an extension to isa and that most modern 
> computers don't have an isa bus but have eisa bus instead, In fact I 
> have a Gateway Computer (500Mhz PIII) that has an eisa slot on the MB. 

Most modern computers do *NOT* have EISA slots.  EISA slots are a very
specialized 32-bit bus that is very rare in anything faster than
200MHz.  I have a 333MHz EISA machine that is the fasted I could find.

A common misconception is that the ISA slot with two parts to it is a
EISA slot.  This is wrong.

> Actually most modern computers don't physically have a slot for either 
> isa or eisa. Quite possibly either one would work. I have 'device eisa' 
> in my conf, it's also 'device eisa' in the GENERIC conf which is why I 
> mentioned it.

Eisa has a completely different configuration structure than ISA.
EISA has .cfg files that you have to load into EEPROM of the
motherboard to tell it what cards are in what slots and what the
resources used by each one are.

The ISA bus still exists in most every machine today, although it is
electrically incompatible with the original ISA bus and isn't an
expansion bus for cards.  It lives on as LPC.  However, FreeBSD still
treats LPC and ISA as the same thing since from a software perspective
they basically are the same.

Adding device eisa can cause problems.  It causes reads to registers
that many really don't implement anymore.  Since windows doesn't look
at these registers, many motherboards have them broken.

Warner