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RE: reg:tick duration
- To: "Natarajan, Mekala (CTS)" <NMekala at chn dot cognizant dot com>
- Subject: RE: [ECOS] reg:tick duration
- From: Gary Thomas <gthomas at redhat dot com>
- Date: Fri, 05 Jan 2001 06:50:57 -0700 (MST)
- Cc: "ecos-discuss at sources dot redhat dot com" <ecos-discuss at sources dot redhat dot com>
- Organization: Red Hat, Inc.
On 05-Jan-2001 Natarajan, Mekala (CTS) wrote:
> hi all,
> i am using i386 as my target processor.
> By default the RTC_period is 100 ticks per second.
>
> For my application i need a tick duration of 20 microsecs..
CYGNUM_HAL_RTC_DENOMINATOR
Note however, that in the current code, this has to be editted by hand
in the file
.../hal/i386/pc/current/cdl/hal_i386_pc.cdl
Change it to be the number of interrupts per second.
Now, the question is why? If you're getting a clock interrupt every 20us,
this code will take probably 5us just to service (I don't have the details,
but this value is indicative of many systems). At that rate, you'll be using
up 25% of your CPU bandwidth (it may be much worse), just servicing clock
interrupts. Again, why do you [think you] need a clock interrupt every 20us?