[time-nuts] GPSCreations SDR (software defined receiver) GPS1A
hmurray at megapathdsl.net
Thu Jan 20 22:10:30 UTC 2011
> real time processing of *anything* is challenging, even if it's only
> updating once an hour. I write this because updating once an hour implies
> you are probably looking at data spanning months, and keeping a program or
> set of programs reliably running without a hiccup for months is
> non-trivial. Sure, we've all got anecdotes of "my machine only needed to
> be rebooted 6 months ago", but there's a difference between seeing that in
> the past, and guaranteeing it for the future.
It should be obvious to anybody who has been working on computers for a
while, but I still remember how surprised I was when I figured it out. (That
was close to 40 years ago.)
The stability of a system is strongly correlated with how often you change
Fixing bugs is probably good. Adding features is not.
It's reasonably easy to get a mature OS to stay up for a long time if you
aren't asking it to do a lot of work. So get a separate PC for your data
Assuming your software is solid, somewhere on the scale of a month or a year,
things like power and/or air-conditioning become the limiting factors.
(Cleaning up or rearranging your lab may also be significant.)
I've been lucky recently. My power hasn't gone out for over a year. They
upgraded the transformer out front ~5 years ago. I think it was a lot
flakier before then, but I don't have any data to back that up.
If your power is flaky, get a UPS. Be sure to check the numbers. The
typical home UPS has a small battery. It runs long enough to ride over short
glitches (seconds) and/or let you cleanly save your work and shut things down
(few minutes), but it won't last hours running a typical PC and display.
If you are interested in long run times on a UPS, consider a low power PC.
The ones I've seen are generally called "embedded". They take 1/2 to 1/3 the
power of of a typical PC at 2x to 3x the cost of a refurbished PC. Via chips
are popular. There are also several very low power ARM systems.
These are my opinions, not necessarily my employer's. I hate spam.
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