Jonathan Gray <[email protected]> wrote: > On Fri, Aug 26, 2022 at 10:21:32PM -0500, Scott Cheloha wrote: > > I noticed that on non-LAPIC systems we program channel 0 in periodic > > mode with an initial count of 11932 to effect a 100hz clock interrupt. > > And then we also use that same channel to count time, but because we > > aren't using the full 16-bit range we need to do all this checking and > > incrementing to handle premature overflow to make it appear as though > > the full counter is being used. > > > > And I had this whimsical idea: gee, wouldn't it be so much easier to > > use channel 0 for clock interrupts and a different channel for > > counting time? > > > > But then I started reading and saw that channel 1 had a dedicated > > purpose in the bad old days. > > > > So I was left wondering when channel 1 stopped performing that task, > > and whether those systems (a) predate the APIC and (b) can even run > > OpenBSD at all. > > Attempting to use counter 1 would be more trouble than it is worth.
I would not be surprised if there existed machines with broken counter 1 (in some subtle way).
