On Tue, Mar 28, 2000 at 12:16:41PM -0500, Thor Lancelot Simon wrote:
> Interestingly, I have a system here with a parallel printer attached that
> has 64MB of buffer memory.  I have seen over *40,000* IRQs/sec from the
> lpt device on this system, while the system feels completely usable.  It
> can't just be the number of IRQs.

My home machine, cyrix 133 with a promise Ultra/33 IDE adapter can handle
4000 IDE IRQ/s without troubles. I'll have to run my bench on my system at
work tomorow.

> This might explain why some SCSI controllers avoid this problem: when you
> get an interrupt, it's quite likely you may find out that multiple commands
> have completed.

Yes ...

> 
> > > With SCSI disks, they don't
> > > seem to appear in the first place.  I'd suspect some kind of odd barrier
> > > condition with !B_ASYNC buffers, but since we don't do disconnection or
> > > multiple command queueing on IDE that doesn't seem likely, either.
> > 
> > What SCSI controller do you use ?
> 
> A variety of them: ahc, bha, and adw.  I haven't seen the problem we're
> discussing with any of them.  I run 'ahc' with tagged queueing turned on,
> BTW.

Interesting, both systems where I notice the problem are K6/II running on a
P5A motherboard. One of them is IDE (Ultra/33) the other SCSI (aha2940UW).

--
Manuel Bouyer <bouyer@antioche.eu.org>
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