Self restarting property of RTOS-How it works? - Page 4

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Re: Self restarting property of RTOS-How it works?
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Already done, in the tall buildings.  There the problem is to
conserve elevator shaft space.  Works something like airline hubs
and feeder lines.

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

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And I've seen proposals (still in the gee-whiz) stage to have an "up"
shaft, a "down" shaft and a few cross-shafts, with motors in the
elevator cars so they have more autonomy for getting up and down.

It was a popular science kind of thing -- I have no idea if it's being
seriously developed (but it'd be fun to do the software!).

--

Tim Wescott
Wescott Design Services
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Re: Self restarting property of RTOS-How it works?
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Google "wonkavator"  (:




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

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That is a different solution.  What you are talking about is "stacked"
elevators, where you have to get off at some intermediate floor and switch
to another elevator.  That is the only way to conserve shafts.   What I was
talking about was where all the elevators went to the lobby, but only to a
subset of the upper floors.  Doesn't conservve shafts, but reduces total
time for those wanting to go to the upper floors, as they don't have to wait
through all the stops on the lower ones.

--
 - Stephen Fuld
   e-mail address disguised to prevent spam



Re: Self restarting property of RTOS-How it works?
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The WTC AFAIK had two sorts of elevators: express ones, which could go up to
levels divided by 20 or so (each of them single source/single destination,
so that the elevators took less from the office space in the precious upper
floors), and slower ones, which shared the shaft space, and could only
reach up within the express lift granularity. To use the vertical space
even better, it could be possible to have a several-level express lift,
i.e. with entrances in several levels, but still with the +-20 floors (or
whatever) granularity.

If I was to build a skyscraper, I would build a big, fast, several-level
wide-granularity express elevator (a "vertical subway") in the core of the
building, complete with own air supply and water coolant for fire emergency
use, and the slow elevators as panorama elevators on the outside. That way,
no shaft space is used for the slow elevators (all elevator doors are
windows when no elevator is there).

--
Bernd Paysan
"If you want it done right, you have to do it yourself"
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Re: Self restarting property of RTOS-How it works?
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I've been in two buildings in recent years where the elevator user interface
works just in that way. One is ~30 stories, but the other is only 14, IIRC.
Both have access control via RFID cards, and those cards can be programmed
to either just allow a single floor - no need to enter the data then - or
a range of floors. Once the desired floor has been entered (explicitly or
implicitly), the display will show the letter of the elevator that will
service you. For larger parties, it is recommended to enter the data more
than once.

    Jan

Re: Self restarting property of RTOS-How it works?
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Well there is enough UML examples around to help them with that problem!

--
Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
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Re: Self restarting property of RTOS-How it works?



glen herrmannsfeldt wrote:

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Some elevators are very well programmed indeed:

http://www.elevate.peters-research.com /
http://www.elevate.peters-research.com/News/newfeatures.htm


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

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Poisson is unlikely to be a good model unless there are a large number
of independant flows passing through the link.

Given the problem's parameters I'd expect only a few flows to be present.

The distribution of inter-packet gaps will depend on the behavior of the
source, the sink, and on other factors such as the and-to-end round trip
delay between the systems.

citeseer found a lot of possible papers on the topic.  this one
seems to be directly relevant:

http://www.cercs.gatech.edu/tech-reports/tr2004/git-cercs-04-09.pdf

and this looks like one of the first to say "hey, poisson doesn't fit":

http://www.cse.ohio-state.edu/~jain/papers/train.htm

                        - Bill

Re: Self restarting property of RTOS-How it works?
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It can be better than might appear, even in such a case.  But you
(and others) are perfectly correct that it is not necessarily a good
model - it depends.

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Yes.  And even more on interactions between the packets, whether in
the sources, the sinks or the transport.

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That's only because of ignorance of previous work.  Most of the
serious work in this field was done decades ago by statisticians
working in the telecommunications industry - there was a vast body
of knowledge when I did my diploma in statistics (c. 1970), with
both a great deal of theory and experimental data.


Regards,
Nick Maclaren.

Re: Self restarting property of RTOS-How it works?
Please note that the attributions got messed up below.  In particular I
didn't say the statement attributed to me that starts with "It's
interesting..." and continues with "my background...."

top posting seemed appropriate here.
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fields
higher.
computer
the
receives
checks
can
long
last?
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lengths.
computer
system?
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true!)
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never



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



del cecchi wrote:

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That tends to happen to people who set their line wrap too small
and thus mess up the number of ">" characters in the replies.

Or, to put it another way...


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people
replies.




Re: Self restarting property of RTOS-How it works?
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No, it happens to those who use a newsreader too dumb to not wrap
quotations, and to quotations from those readers too dumb to wrap
the originals at 65 or so.

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



CBFalconer wrote:

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I was hoping to get the post-mangler to see that he has a problem
before getting into the specifics of the best way to solve it.
This being Usenet, there is a large chance that the thread will
continue with: "I *like* mangling repies!  It's convenient!"  :(





Re: Self restarting property of RTOS-How it works?
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here is example of a configuration and workload analysis
http://www.garlic.com/~lynn/99.html#67 System/1 ?
http://www.garlic.com/~lynn/99.html#70 Series/1 as NCP (was System/1?)

with the help of performance predictor and configurators on
hone:
http://www.garlic.com/~lynn/subtopic.html#hone

hone was the online system(s) that provided support for world-wide
sales, marketing, and field people.

performance predictor was outgrowth of work at the science center on
performance management, workload profiling, the early technology
transition from performance management to capacity polanning:
http://www.garlic.com/~lynn/subtopic.html#bench

that allowed sales people to input customer configuration and
operational information (often softcopy extracted from the system
itself) and be able to do what-if questions about changes to
configuration and workload.

as hardware got more and more complex ... configurators were the
applications that allowed a sales person to specify rough product
specification ... and the application would make sure that enuf
correct information was supplied for ordering the equipment.

now, this particular analysis ... i presented at the SNA architecture
review board meeting in raleigh and took lots of arrows on.

the reference about keeping timing sync ... is somewhat related when
the telcos stopped letting customers have clear-channel T1 links and
required them to conform to the ones-density (and 193rd bit)
specification.

--
Anne & Lynn Wheeler | http://www.garlic.com/~lynn /

Re: Self restarting property of RTOS-How it works?
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If it's internal clock can't stay synchronized over 5 seconds, or
even much longer, I think there is something wrong with the
hardware design.  Of course you haven't defined synchronized.  I
certainly couldn't answer it, but I would know enough to hunt up
queueing theory, which is quite mature and predates computers.
Whatever the synchronizing requires, I would attempt to put
something in the transmitter system to ensure satisfaction.
Statistics can always burn you.

But you are asking the wrong question.  However, if you asked what
is the probability that 10 packets will arrive in 5 seconds, you
would have a good point.  Again, the place to look is queueing
theory.  I do know that the design is going to require some sort of
buffering, and if there is nothing else critical and resources are
pre-established I will assign as much buffer space as possible
(assuming no other similar requirements) and not bother with the
details.

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Re: Self restarting property of RTOS-How it works?
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I think I misconstrued your 'synchronized clock'.  You are not
talking about time, but about a data clock, i.e. a strobe.  In this
case I consider the whole design flawed, because once more I don't
want to trust to statistics.  The transmitter should be emitting a
preamble to synchronize the clocks.

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Re: Self restarting property of RTOS-How it works?
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Yes, it need not be sensitive to inter-packet timing.
It has been about 25 years since I looked at this stuff, but that
sounds like IBM Bisync which used two SYNC bytes (thus bi-sync)
to train the clock. I don't recall how Bisync avoids mixing up
data with SYNC bytes.

In HDLC/SDLC uses 01111110 as a special flag value. To ensure it
does not mix with the data, when it the xmitter sees 5 '1' bits in
a row, it jams in a '0' bit. The receiver later drops the jammed '0'.
NRZi encoding represents a '1' as no change and a '0' as a change
(inverting of state) in level. Combining SDLC and NRZi ensures there
is a transition at least every 5 bit times so a Phased Locked Loop
can recover the clock from the data stream.

Other data encoding methods, such a FM0, FM1 or Manchester (used by
Ethernet) ensure there is a state transition for each bit so the
clock can always be recovered by a PLL. However these double the
transmission frequency.

Eric


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

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It think it's extremely unfair to blame comp-sci for linked lists and
and buffer overflows; most of that stuff was invented before comp-sci
was being taught.

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My favourite example: people without comp-sci hardly ever get
floating point comparison right.

Casper
--
Expressed in this posting are my opinions.  They are in no way related
to opinions held by my employer, Sun Microsystems.
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Re: Self restarting property of RTOS-How it works?

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architecture
paradigm
store
multiple
talking
But who was it that put linked lists and fixed size buffers with
undefined size inputs  in widely used software?  Engineers?
I can't imagine just reading until end of record with no control or
checking on  the input.  A program that dies due to the ping of death?
Who wrote this  stuff?  Did they test it?  And years later we still have
it?

I'm not trying to insult folks or start a flame war but some of these
things boggle the mind.

del cecchi



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