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SubjectRe: A/D converter
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Richard B. Johnson wrote:
> On Wed, 21 Apr 1999, Rogier Wolff wrote:
>
> > > On Tue, Apr 20, 1999 at 01:13:40PM -0400, Richard B. Johnson wrote:
> > > > There is, furthermore, no reason to do so. The fact that the original
> > > > inquiry was about an ADC that "ran" at 70 kHz, means nothing about
> > > > the speed at which it was expected to interrupt. In fact, the
> > > > maximum rate at which you can interrupt Linux, and record that an
> > > > interrupt occurred in your ISR (nothing else), is almost, but not
> > > > quite, 50 kHz on a dual pentium running 400 MHz with a 100 Mhz main
> > > > bus. I have a device-driver module which does little more than measure
> > > > these kinds of things if you are interested.
> >
> > A Pentium-100 SBC, on a passive-ISA backplane can do about 140k
> > interrupts per seconds.
> >
> > The case where I tested this, I had to do a few ISA IOs to acknowledge
> > the interrupt, so the interrupt routine was NOT completely empty.
> >
> > This was autumn '96. I think the machine runs 2.0.18.
> >
> > Roger.
>
> Look. I am not going to get into a contest about this, but the I have
> a simple module device driver that gets an interrupt from the printer
> port (which it doesn't have to ack), and increments a longword to
> keep track of interrupts (nothing else).


Look. I am not going to get into a contest about this, but I measured
this on just one machine a while ago. The only machine with the proper
hardware to measure this was the Pentium 100 in the Passive ISA
backplane. I no longer have access to that machine (armed guard at the
door, that kind of stuff (*)).

I even mentioned the kernel version and some of the relevant
components of the computer that I measured this on, so if you are
serious about wanting more performance than the 50k that you measured,
I suggest that you try that old kernel. If that doesn't help, I
suggest you try a simple pentium on a triton motherboard.

If you're no longer interested in the "number of interrupts that Linux
can serve" or if you simply don't trust me, fine. Just ingore my
"datapoint", and go about your merry way. But unless you've got
some more information, I'd rather you not imply in public that my
measurements are wrong.

Roger.


(*) the major reason why the machine can run old software like 2.0.18
with the similarly old distribution.

--
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
------ Microsoft SELLS you Windows, Linux GIVES you the whole house ------

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