[comp.sys.dec] Clock interval on MIPS workstations

vancleef@iastate.edu (Van Cleef Henry H) (06/10/91)

I originally posted this question on comp.unix.ultrix but have gotten no
responses.

I am using the difference between two gettimeofday() calls to measure
real-time performance.  What is the number of microseconds added each
time the clock ticks.  

This question applies to 2100, 3100, and 5000 MIPS DECstations running
Ultrix 4.*.  
-- 
Hank van Cleef  
vancleef@iastate.edu	Iowa State University, Ames. Ia.
tmn!vancleef		The Union Institute, Cincinnati, Oh.

mellon@nigiri.pa.dec.com (Ted Lemon) (06/11/91)

>From personal experience I know that this is not the best you could wish for
>if you are doing real-time measurements. An alternative would be to put a
>real-time clock module on the optional VME bus on the DECstation 5000.

Gack!   That sounds like *serious* overkill!   Why not just put one on
the TurboChannel?   The amount of electronics that you'd be adding to
your DS5000 to perform this simple little function is frightening to
contemplate...

			       _MelloN_

pilmeyer@utrtsc.dec.com (06/11/91)

In article <MELLON.91Jun10135634@nigiri.pa.dec.com>, mellon@nigiri.pa.dec.com (Ted Lemon) writes...
> 
>Gack!   That sounds like *serious* overkill!   Why not just put one on
>the TurboChannel?   The amount of electronics that you'd be adding to
>your DS5000 to perform this simple little function is frightening to
>contemplate...

Yes, I agree. However there is one very good reason to go for a VME clock
module instead of a TurboChannel module: There is no clock module for the
TurboChannel (at least not when we needed it).

-Han

mcculley@alien.enet.dec.com (06/12/91)

In article <1292@sousa.ltn.dec.com>, pilmeyer@utrtsc.dec.com writes...
>In article <1991Jun9.233056.12085@news.iastate.edu>, 
>	vancleef@iastate.edu (Van Cleef Henry H) writes...
>>I am using the difference between two gettimeofday() calls to measure
>>real-time performance.  What is the number of microseconds added each
>>time the clock ticks.  
>On the MIPS based DECstations the clock runs at 256 Hz. [...]

Henry's original question mentioned that the same question was posted to
comp.unix.ultrix but got no responses.  For the sake of completeness it
probably should be mentioned here that there was a subsequent answer there
(from Jeff Mogul) that not only gave the same information as Han's post here,
but also added that other clock rates were possible and offered a modified
clock driver to implement them.

--bruce