[time-nuts] Beaglebone NTP server

Hal Murray hmurray at megapathdsl.net
Thu Dec 11 16:23:25 EST 2014


jimlux at earthlink.net said:
> Ah, but will the exact same single board computer be available for
> replacement in 5 years?  Or will it be Rev F instead of Rev B, with  "just a
> few tweaks to improve performance", but also enough that it's  not "drop the
> image on it and run"

> What about 10 years? 15? 

My straw man is to buy a bunch now and put them on the shelf until you need 
them?  It would be interesting to read a good B-school type report on that 
topic.

Is it realistic to expect any electronics related stuff to be available for 
10 years?  I think I've seen a few boards marked long-lifetime.  I don't 
remember the details.  At least one OS distro has a version marked 
long-lifetime, but I don't know how long that covers.

What does the military do for this problem?  What's the average lifetime of 
something like a radio in a military plane?  How often do they get upgraded 
because the old ones are no longer maintainable due to unavailability of 
parts?

What's the average lifetime of a fab line?  Or even the max lifetime?  (in 
case you are a big vendor with multiple fab lines for a particular technology)

What's the typical lifetime of parts used in timing related gear?


> Maybe that's the key.. think of it as an appliance. If it stops working,
> and it's not because of something simple (power cord), then you're  probably
> better off building a new one from scratch than trying to fix  the old one.

> That is, the labor involved in "port to a new platform" might be
> substantially less than "find old platform and install it in old box",  if
> only because things like tool chains tend to follow the latest hardware. 

A lot of that depends on the quality of the documentation you kept when you 
set things up.

I've worked with guys who were good at making a big pile of kludgy gear jump 
through hoops.  One of them was very good at writing down what he did.  It 
doesn't have to be a fancy document blessed by 43 proofreaders, but it really 
helps to mention all the critical steps and/or explain the non-obvious 
reasons for doing things.

I've gotten into the habit of making a checklist of what I have to do to 
install distro-X from CD and fix it up to do what I want.  Every now and 
then, I want another box just like that one except...

It isn't fancy, but it does have a line to remind me about each file that 
needs editing and what tools are used to set things up.  Often there are 
chunks of code I can cut-paste.


> Even if you kept the tool chain for your old platform, running it on a  new
> computer might be problematic. (recognizing that there are people  out there
> running IBM 1401 emulators on System/360 emulators on... but  that takes
> time too) 

It's not uncommon to archive the PC that has all the tools when a significant 
hardware project is released.  Just put a big note on it and push it into a 
closet in case you ever need it again.  (Setting up CAD tools is often quirky 
and hard to debug.)  Again, this needs documentation.  Suppose you want to 
make a simple one line change to fix a typo.  What do you do to turn the 
crank and make the files you hand off to the next step?




-- 
These are my opinions.  I hate spam.





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