kernel vs. user processes

[rdm@tad.micro.umn.edu]

It's interesting to note that Linux implements vga as user code rather
than kernel code -- primarily for speed.

Note that the limitation of this approach is that only one "program"
can directly access vga at any one time.  And, furthermore, that
program must explicitly give up control before another program can
begin using the system.  Thus, during development of vga code, a
program crash can leave the display in an unusable state.

(Partially, this is because a number of manufactorers of vga hardware
have been reluctant to provide low-level programming info.  Partially,
this is because some vga hardware can be "locked up" if the wrong
things are done with it.)

This isn't as elegant an approach as taos, of course, but it's an
interesting variation.

-- 
Raul