[time-nuts] Thought experiment on a low cost timing board

[Tim Shoppa]

Hal Murray <hmurray at suespammers.org> wrote:
> > PCI 3.3v board with:
> >     10Mhz OCXO (provision for external clock source?)
> >     Uart (serial is an endangered on many PC's)
> >     Free running counter driven from the OCXO and readable by PC
> >     inputs to latch the counter (how many?) with the latched result
> > also readable (for PPS) 
>
> I've been daydreaming along the same line but haven't hit a combination of 
> ideas that feels good enough to actually do anything.
>
> My list has a FPGA in the middle.  The problem with that is that newer FPGAs 
> don't work on 5V PCI which is what all of my PCs have.  The only 3V slots 
> I've seen are in high end (noisy, expensive) servers.  The PCI slots on 
> Soekris boards are 3V.  That adds another option to think about.
>
> There are several possibilities for dealing with 5V PCI.
>[ BGA's, Gold Fingers, etc.]

My gut feeling: back up a little bit. Figure out how to do what you
want without a PCI bus, without gold fingers, without BGA's, etc.

I have to admit, it's been so long since the beginning of this thread
I forgot what the original goal was!

It would seem rather straightforward to, for example, make a small board
that will let you timestamp events without having to muck about
with PCI etc. at all. Output could be serial/parallel/USB/whatever
you like.

General-purpose I/O ports that plug into PCI busses are available
and while they aren't generally cheap (start around a few hundred $)
it's a lot less hassle and cheaper in the end than laying out your 
own PCI board to do the same!

And ISA bus computers are still around. You won't find them at
CompUSA but it's a lot easier to prototype simple stuff for ISA
bus.

Tim.