Messages in this thread | | | Date | Wed, 21 Apr 1999 08:32:39 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: A/D converter |
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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).
I hook a function generator to the printer port. The ioctl input to the device atomically reads the longword and resets it to zero. The a user-mode task reads this at 1-second intervals.
The maximum number available is slightly less than 50,000. This is on my fastest dual-pentium 400 Mhz. Other machines I have tested are slower.
Using the same technique, in a DOS-booted machine, in which the ISR does nothing but uncrement a word in memory and resets the controller with a specific EOI, I can get slightly less than 400,000 interrupts per second.
This is not an estimate, this is not a guess. This is real. I have the data, the source-code, and everything else to prove it. If you want the source-code let me know.
Cheers, Dick Johnson ***** FILE SYSTEM WAS MODIFIED ***** Penguin : Linux version 2.2.6 on an i686 machine (400.59 BogoMips). Warning : It's hard to remain at the trailing edge of technology.
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