Self restarting property of RTOS-How it works? - Page 2

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Re: Self restarting property of RTOS-How it works?
says...
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Not really.  A lot of the processor may be synthesized from HDL, but
much is in custom circuits with perhaps an HDL model of the custom
circuit for simulation.  Either way, you can't reboot them from a new
HDL file either.  Silicon's got to change.

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Sure. Statistical models are used in the design process.  Sometimes one
designs to a number that's even better than the process mean (I suppose  
that's your definition of "typical"). If one designed for worst case
nothing would work because it would never be built.

--
  Keith
 

Re: Self restarting property of RTOS-How it works?

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Or for an example of hardware errors in a mature industry,
consider the hundreds or thousands of car recalls that occur globally
each year.

Re: Self restarting property of RTOS-How it works?
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 > hundreds or thousands of car recalls that occur globally each year.

Slightly different issue. This occurs because with more units deployed,
you manage to hit those areas of failure that before were inaccessible,
due to simple statistics. Many of the software failures I've seen, on
the other hand, are of the trivial kind a cursory user would find in a
few minutes to days. (In)famous was one of the major VMS releases - V5,
if I remember correctly - where it took three people from our institute
literally minutes to find a dozen bugs or so ranging from the annoying
- changing the password gave the success message twice - to the grave
- doing something slightly unexpected on the command line lead to a
reproduceable system crash. We wondered what that year of internal and
external field test had been wasted on.

    Jan

Re: Self restarting property of RTOS-How it works?
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Reminds me of the last GM car I will ever own, which happened about
25 years ago.  Within the first 500 miles it had seized the front
brakes (that took less than 10), destroyed a fan belt pulley (with
no replacements in the parts stream, jury rigged with a weld.  Two
months later they had a replacement pulley).  Within 10,000 miles a
front door had literally fallen off.  By 60,000 miles the engine
block was cracked due to a non-functional freeze plug (this was
also due to a careless mechanic who changed the coolant to pure
water in the summer while repairing the failed heater).

--
"If you want to post a followup via groups.google.com, don't use
 the broken "Reply" link at the bottom of the article.  Click on
We've slightly trimmed the long signature. Click to see the full one.
Re: Self restarting property of RTOS-How it works?
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You suffer from a misunderstanding.  Those things in the block of an
engine are there to get the sand out when casting.  They are not there
to protect the block from cracking if the coolant freezes.

So the plugs are artifacts of the manufacturing process and not idiot
savers.  You didn't check the coolant in the fall?  In the days you
refer to "25 years ago" it was customary to change coolant every fall.
Probably even listed in the manual.  You do read manuals, right?

And even a honda or a mercedes will crack the block if the coolant is
wrong.  GM had nothing to do with it.

Now about the 200 series transmission in my 77 Impala.....

del

Re: Self restarting property of RTOS-How it works?
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I have noted previously here in c.a that most of the _really_ good
low-level/systems programmers I know seem to have an engineering instead
of computer science background.

A coincidence?

Terje

--
"almost all programming can be viewed as an exercise in caching"

Re: Self restarting property of RTOS-How it works?
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I have also noticed that the programmers from a computer science
background tend to be much better at working out a system architecture
and planning first.

My hypothesis:  the more detail-oriented people tend to gravitate toward
the engineering side, and tend to excel at detail-oriented tasks, while
the computer science people tend to be better at big picture and
abstract concepts.

Just MHO.

Ed


Re: Self restarting property of RTOS-How it works?

|> Terje Mathisen wrote:
|> >
|> > I have noted previously here in c.a that most of the _really_ good
|> > low-level/systems programmers I know seem to have an engineering instead
|> > of computer science background.
|> >
|> > A coincidence?
|>
|> I have also noticed that the programmers from a computer science
|> background tend to be much better at working out a system architecture
|> and planning first.

!!!!  My experience is that they are generally CATASTROPHIC at that;
MUCH worse than even engineers :-(

Oh, yes, they work out an 'architecture' and a 'plan', but it is
usually based on a completely unrealistic view of the world, where
nothing ever goes wrong and nobody ever makes a mistake.  The worst
fault is usually that they regard it as reasonable to omit all error
recovery, diagnosis and robustness, and claim that going bananas is
a perfectly reasonable response to a natural human error.

Also, they regard it as perfectly reasonable to produce interfaces
that positively encourage such errors, and fail to see that it is
the responsibility of a designer to ensure that the product is (as
far as is possible) easy to use and fail-safe in operation.

There are a FEW meritorious exceptions, and some computer science
academics who would love to change this but are constrained by
the pressure to produce graduates with the widest possible
(theoretical) knowledge in the shortest possible time.  You CAN'T
teach an engineering attitude in a short lecture course - it needs
practical training, and lots of it.

|> My hypothesis:  the more detail-oriented people tend to gravitate toward
|> the engineering side, and tend to excel at detail-oriented tasks, while
|> the computer science people tend to be better at big picture and
|> abstract concepts.

I.e. producing ridiculously unrealistic designs and leaving all
the real work to someone else.


Regards,
Nick Maclaren.

Re: Self restarting property of RTOS-How it works?


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[snip]

Nonsense.  You can't tar an entire class of people based on the
worst examples.  And I say that as an engineer who knows enough to
let the computer science fellows do what they do best.



Re: Self restarting property of RTOS-How it works?

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A) I was not referring to the worst examples - I have seen much,
MUCH worse examples than that.

B) I did NOT tar the "entire class".  If you had not been so keen
on being snippy, you would have included (or at least read) the
paragraph where I said that there were exceptions, as well as
computer scientists who regret the situation.  And, incidentally,
the paragraph you quoted contained the little words "generally" and
"usually" - they mean something, you know.

C) I have considerable experience with dealing with such people,
in academia, commerce and elsewhere.  Some of my colleagues and ex
colleagues have been among the best - but are YOU prepared to justify
the design of the X Windowing System, to take one prime example of
what I was referring to?

On the last point, the kindest thing that can be said about its
software engineering is that it was never intended to be used in a
commercial production context.


Regards,
Nick Maclaren.

Re: Self restarting property of RTOS-How it works?
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There is no substitute for hiring competent people, no matter what their
background.

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By implying that design work is not "real work" you have just proved my
point.

Ed


Re: Self restarting property of RTOS-How it works?
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If you had been following this group for even a short while, you
would realise how foolish that makes you look.  I don't believe that
anyone could believe that I would post such an implication, though
trolls would claim it - though I am NOT claiming you are a troll,
merely mistaken.

As every experienced designer, engineer and so on will know, there
is a world of difference between a "broad brush" outline and a precise
template.  One difference between a good designer and a bad one is that
the former's outlines can be developed into something practical, and
the latter's often can't.


Regards,
Nick Maclaren.

Re: Self restarting property of RTOS-How it works?



Nick Maclaren wrote:
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I don't think it makes him look foolish at all; I read the same
meaning into your words.  The fact that your reply borders on
being a personal attack rather than striving to correct any
misunderstanding adds weight to Ed's interpretation.

You exhibited the same behavior towards me when you wrote

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Note that this was in a thread posted to comp.arch.embedded with
the phrase "RTOS" in the subject line - off-topic as well as
being overly confrontational.

I advise you to examine your posting style.  It is not conducive to
a civil and reasoned technical discussion of the subject at hand.

"A little rudeness and disrespect can elevate a
meaningless interaction into a battle of wills
and add drama to an otherwise dull day."
                       -Calvin discovers Usenet



Re: Self restarting property of RTOS-How it works?
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Let me explain in VERY, VERY simple words.

One of my hobby horses is the need for a precise computational model
before starting any design, and another is the need for precisely
defined, logically consistent specifications.  I am probably rather
a bore on both of them, and anyone following comp.arch for more
than a few days would have difficulty not noticing my views.  Enough
threads where I have banged on about those have been cross-posted
to comp.arch.embedded that I am surprised you haven't noticed.

Secondly, the fact that both he and you read the same thing into my
words merely shows that you are unaware that design comes at many
levels.  Even if you were to regard them as ambiguous (which IS
reasonable, if you were unaware of my views), it is absolutely clear
that there were two interpretations.  At least if you have any
experience of designing practical, complex systems, that is.

I have pointed out the difference between "broad brush" and detailed
designs in other postings, and don't plan to expand them here.  But,
if you are unaware of the vast number of the former that have been
produced by computer scientists and have been quite impractical to
turn into working, detailed designs, then I am afraid that I have to
say your experience is severely limited.


Regards,
Nick Maclaren.

Re: Self restarting property of RTOS-How it works?



Nick Maclaren wrote:
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No.  I won't let you do that.  I have no further interest in reading
anything else after the above, so I hit the delete to end of file key
without reading the rest of your post, and I will now hit the killfile
key so that I will not see any future posts by you.  Bye-bye, flamer.

*plonk*



Re: Self restarting property of RTOS-How it works?
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Those comp-sci geniuses are the ones that gave us a software paradigm
that is susceptible to attacks as simple as buffer overruns, and store
data in randomly scattered chunks linked by pointers.   And put multiple
unrelated locks in the same cache line?  That the ones you are talking
about?

Del cecchi

Re: Self restarting property of RTOS-How it works?
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[...]
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It's interesting to learn that no engineers were ever involved in
building such flaws.

My background happens to be more in the engineering than the computer
science end of things, but I don't share your evident contempt for the
field.  Here's an example:  An embedded communication system receives
packet-based messages of varying lengths at an average rate of 100
packets per minute, but asynchronously.  Because the system also checks
its timing against the recovered clock from the messages, which it can
easily keep synchronized within limits as long as it doesn't go too long
without receiving a packet.  What is the probability that no packets
will arrive in an interval of five seconds?

I can answer that question easily because I've studied a little computer
science.  Can you?  If not, how can you properly engineer the system?

Ed


Re: Self restarting property of RTOS-How it works?
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Re: Self restarting property of RTOS-How it works?
snipped-for-privacy@fastmail.fm writes:

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well, i can tell you that it has no floating point and that its memory
bandwidth sucks. and that your nose falls off if you use it.

--
    mac the naïf

Re: Self restarting property of RTOS-How it works?

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architecture
paradigm
store
multiple
talking
checks
long
computer
Well, first I would want to know the average utilization of the link.
Then I would want to know the distribution of the lengths of the
packets, and the distribution of the rate at which they are sent.  If
the distribution is that the utilization is 0.1 percent and the packets
are all sent once a minute by a batching system then the probability is
100 percent.  On the other hand if the utilization is 99.9 percent and
the distribution is uniform, then the probability is very low.

Yes, I too have studied some computer science.  The first time I saw
some of the algorithms, and the scheme language, I almost plotzed.

del cecchi
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