Sorry I've replied to this message but I didn't include some knowledge
thinking it was implicit:
No PC has had a true serial port for years. Probably decades. For a very
long time "this stuff" (ISA slots, which are basically a bus for a
really old processor - that guy I mentioned in the other message knows
more and I'm happy to ferry questions if you like) has been done by
"superIO" chips and suchlike. It's not been a direct interface to the
processor probably for a good 20 years.
Any "serial ports" you have will be over PCI anyway (which may or may
not be PCIe - this doesn't really matter) - you'll want to make sure
it's not behind a bridge though.
It's worth remembering that crap being pushed out of the cache will
cause significant variance, this is well known in ethernet circles as
getting something to deal with 10gbit/sec ethernet is non-trivial. There
are things like DMA'ing right to the cache.
So RE: the serial port - that ship has sailed, but I'd be curious to see
a USB and a PCIe one compared for example.
Alec
On 05/11/2021 05:36, Rich Wales wrote:
Looking to design my next Linux (Ubuntu) system, built around a Ryzen
processor.
In previous systems, I've had great success using a Garmin GPS 18x
unit (small hockey puck with a wire tail) hooked up to a DB9 serial
(COM) port on the motherboard, to provide a local (stratum-0) time
reference via gpsd and chronyd. However, mobos with a serial port are
becoming harder to find.
(Yes, I know that PCI serial port cards exist -- however, these are
not suitable for connecting a GPS time reference because the PPS
signal timing is unpredictable -- so I've limited myself to using
motherboards with a builtin serial port.)
What Ryzen (Socket AM4) motherboards have worked out well for people
who want to do what I'm proposing?
Alternatively, can anyone recommend a better hardware solution than a
Garmin GPS attached via a serial port?
Thanks for any suggestions.
*Rich Wales*
ri...@richw.org
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