On Fri, Jul 09, 1999 at 05:28:15PM +0000, Paolo Mantegazza wrote:
> Victor Yodaiken wrote:
> > You can prove whatever you want, but I have timed a single outb to the isa
> > interface at 12microseconds on a PII LX chipset.
>
> Dear Victor,
>
> let have it this way.
>
> Under RTL the you can run, on a PPRO 200, a single bit toggling task at
> up to 120 Khz in periodic mode, but in the oneshot mode at 20 Khz it is
> short of breathing.
>
> Under our RTL variants, and RTAI, that is roughly 120/95, and the ratio
There are several variables
1. Test. If you run a simple test
rdtsc
outb
rtsc
on all the x86 motherboards I have tested, you find a worst case delay
of over 10 microseconds if the outb is to the timer. This is a consequence
of the specification of the ISA bus as far as I know. Perhaps, however
I am just unlucky in choice of motherboards.
2. Version of RTL
3. Adjust time. If you are willing to busy wait during Linux periods,
then you can run a periodic task oneshot at a higher frequency. That
is: getinterrupt, while tsc shows not ready loop; run task.
I have not seen a reason to do that beyond a very minor level although
perhaps I am not well informed. If you want a 100Khz task you
have to run the task every 10microseconds anyway. So I don't see
how the oneshot mode gets you anything in that case. Can you
give me an example?
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