Re: how is system geared down?

["Alexei Pytel" <pytel@xxxxxxxxxx>]

This is exactly a problem...
Raw technical data is misleading, as I tried to show - like Mhz etc.
Another way is to measure system performance in relation to a well-defined
benchmark.
Unfortunately, benchmark results only show how well system performs this
particular benchmark, no more no less.
Benchmark results can only be extrapolated to a particular application, if
one understands very well, how *this* application relates to *that*
benchmark - which is very difficult and rarely the case.
Also, benchmark is taken in a particular configuration. Change
configuration of the same box - and suddenly results are different.
Too often benchmark results are taken as absolute measure - say, if system
A performs benchmark X better than system B, then it's faster overall.

However, with all the deficiencies of benchmark approach, it seems so far
the only "quasi-objective" way.

CPW numbers used by Rochseter are based on a strictly defined workload - in
other words they are benchmark-based.
(Don't forget that CPWs are measured for a balanced - most often this means
maximum - configuration.)

Unfortunately, there are too many different workloads nowadays. It's
impossible to aniticipate every use of a computer system and have a
benchmark for every case. Thus the attempt to alleviate this by publishing
Mhz ratings.
In this way one - caveat emptor - can estimate that if system has small CPW
but fast CPU, then *possibly* it *may* perform compute-intensive code
better than it's CPW rating  suggests.

In short - it's so complicated...

    Alexei Pytel

"Pessimist is nothing but a well-informed optimist"




                                                                                
                   
                    "Steve Richter"                                             
                   
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geared down?          
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                    05/11/2001 01:14 PM                                         
                   
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I apologize also Alexie. My commisars comment communicates my low opinion
of
ibm mgmt, whose actions I feel are threatening to make my 15 yrs experience
on this platform obsolete.

you are a great resource for this list alexie. I have learned more about
the
iseries from this thread due to yours and nathans participation.  and I
thank you for it.

Now, could I ask if ibm publishes the cpu speed of its systems?

This could be a relevant question. Example: stocking a low cpw system with
a
lot of memory may allow that system to not page as much on its slow speed
io
channels, hence perform better than its cpw rating.  Or a system that is
used primarily by pgmrs compiling pgms. A compile is a cpu and memory
intensive application. A system used in such a way as this may out perform
its cpw?

best regards,
Steve Richter





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