com3 & com4 -> tty2 & tty3

[David F. Carlson]

In article <42700009 at osiris.cso.uiuc.edu>, dpgerdes at osiris.cso.uiuc.edu writes:
! 
! /* Written  9:14 pm  Apr 19, 1989 by plocher%sally at Sun.COM */
! 
! >You can not use IRQ2 for anything under Unix - it is already used by the
! >system.
! 
!   I am getting tired of people making statements like the above with 
! no explanation.  The only thing I have been able to pin down about int 2 is 
! that the EGA board uses it, if properly enabled.
!   Any ideas as to what is really going on?
!     -dave gerdes

First, as usual, Mr Plocher is correct in that INT 2 is unusable for all
PC/AT architecture machines (as opposed to PC bus.)  INT 2 is used to cascade
a second PIC (Programmable Interrupt Controller) so that the extra interrupts
the AT bus supports can be used.  Perhaps before "getting tired" of hearing
correct advice, purchasing some books on PC/AT architecture might be in order.
A good one is the tech ref manual for Heathkit (Zenith) PC/AT.  Alternately,
IBM would be glad to hose you for several hundred dollars for a similar manual.

-- 
David F. Carlson, Micropen, Inc.
micropen!dave at ee.rochester.edu

"The faster I go, the behinder I get." --Lewis Carroll