Ryzen mobos with serial port for Garmin GPS?
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
richw@richw.org
On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
However, mobos with a serial port are becoming harder to find.
That's not really been my experience, they just moved it to a header.
You will need to supply a DE9 to ribbon cable, say on a bracket, or
installed in a cutout elsewhere in the case.
This is the first one that I checked, and it has such a port labelled
COMA, along the left/bottom edge.
https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
Also note that the Linux PPS driver supports the standard PC parallel
port, which you can usually find as a header. If you are having
performance issues with one, try the other. (But you may need to supply
negative-going edges to the parallel port.)
Have fun,
Darren
Darren Freeman wrote:
/That's not really been my experience, they just moved it to a header.
You will need to supply a DE9 to ribbon cable, say on a bracket, or
installed in a cutout elsewhere in the case./
Some motherboards do indeed have a serial (COM) header, but I've
encountered quite a few that do not. I don't think this can be taken
for granted -- gotta check the specific mobo or its manual.
/This is the first one that I checked, and it has such a port labelled
COMA, along the left/bottom edge.
https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp/
Thanks for this mobo suggestion. I'll keep it in mind.
/Also note that the Linux PPS driver supports the standard PC parallel
port, which you can usually find as a header. If you are having
performance issues with one, try the other. (But you may need to
supply negative-going edges to the parallel port.)/
Thanks. I see that this particular Gigabyte mobo which you suggested
has a parallel (LPT) port, but my impression has been that parallel
ports are really becoming rare (more so than serial ports), considering
that most printers nowadays use USB or Ethernet (or sometimes WiFi).
Rich Wales
richw@richw.org
Personally I think you would be better off with a Raspberry PI solution on
your local gigabit net, however a simple google search for "gigabyte am4
rs232" resulted in the link below. The first two boards in the comparison
table both have serial ports. I have had good experiences with Gigabyte
motherboards, also there was a used GA-AB350-GAMING 3 listed on eBay for
under $70 although the seller didn't have the greatest feedback score.
Thomas Valerio
https://www.gigabyte.com/us/Comparison/Result/2?pids=6166,6167,6225,6227
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
richw@richw.org
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
an email to time-nuts-leave@lists.febo.com
To unsubscribe, go to and follow the instructions there.
A friend of mine who lives and breaths this stuff (I wont tell you what
he does - but suffice to say he's authoritative) basically said to me on
something about serial ports that you can't go wrong with USB stuff,
even on Linux.
Would that work?
Serial ports certainly are getting scarce! You'd get 2 to a board an
embarrassingly long time ago!
On 05/11/2021 06:10, Darren Freeman wrote:
On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
However, mobos with a serial port are becoming harder to find.
That's not really been my experience, they just moved it to a header.
You will need to supply a DE9 to ribbon cable, say on a bracket, or
installed in a cutout elsewhere in the case.
This is the first one that I checked, and it has such a port labelled
COMA, along the left/bottom edge.
https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
Also note that the Linux PPS driver supports the standard PC parallel
port, which you can usually find as a header. If you are having
performance issues with one, try the other. (But you may need to supply
negative-going edges to the parallel port.)
Have fun,
Darren
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com
To unsubscribe, go to and follow the instructions there.
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
richw@richw.org
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
send an email to time-nuts-leave@lists.febo.com
To unsubscribe, go to and follow the instructions there.
Use FTDI USB serial ports - you can't go wrong with them.
https://ftdichip.com/
I have, at the last count, used something like 200 of their FT232 device in
one form or another on the shack PC. I know that, because device manager
has registered up to COM200. Every time a new one is plugged in, a new COM
port is set up.
Andy
www.g4jnt.com
On Fri, 5 Nov 2021 at 18:26, Alec Teal alec@unifiedmathematics.com wrote:
A friend of mine who lives and breaths this stuff (I wont tell you what
he does - but suffice to say he's authoritative) basically said to me on
something about serial ports that you can't go wrong with USB stuff,
even on Linux.
Would that work?
Serial ports certainly are getting scarce! You'd get 2 to a board an
embarrassingly long time ago!
On 05/11/2021 06:10, Darren Freeman wrote:
On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
However, mobos with a serial port are becoming harder to find.
That's not really been my experience, they just moved it to a header.
You will need to supply a DE9 to ribbon cable, say on a bracket, or
installed in a cutout elsewhere in the case.
This is the first one that I checked, and it has such a port labelled
COMA, along the left/bottom edge.
https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
Also note that the Linux PPS driver supports the standard PC parallel
port, which you can usually find as a header. If you are having
performance issues with one, try the other. (But you may need to supply
negative-going edges to the parallel port.)
Have fun,
Darren
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
send an email to time-nuts-leave@lists.febo.com
To unsubscribe, go to and follow the instructions there.
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A bit more :
I think the serial interface, via an FTDI chip device, makes for one of te
most versatile interfaces you could go for. Serial ports are supported in
every programming language so are generally easy to set up in software
without having to install DLLs.
The FTDI devices will run at up to 3000000 Baud, whereas the original
'real' RS232 was only ever 115200 baud max.
I have even used mine for 10 bit digitised audio at sampling-card rates
sent on RS422 twisted pair . It was simpler to programme than using a
soundcard would have been.
One FTDI device allows 8 bit parallel access that 'looks' to the PC like a
serial port. Never tried this myself, but a number of manufacturers have
implemented PC interfaces using this route.
Andy
www.g4jnt.com
On Fri, 5 Nov 2021 at 18:32, Andy Talbot andy.g4jnt@gmail.com wrote:
Use FTDI USB serial ports - you can't go wrong with them.
https://ftdichip.com/
I have, at the last count, used something like 200 of their FT232 device
in one form or another on the shack PC. I know that, because device
manager has registered up to COM200. Every time a new one is plugged in, a
new COM port is set up.
Andy
www.g4jnt.com
On Fri, 5 Nov 2021 at 18:26, Alec Teal alec@unifiedmathematics.com
wrote:
A friend of mine who lives and breaths this stuff (I wont tell you what
he does - but suffice to say he's authoritative) basically said to me on
something about serial ports that you can't go wrong with USB stuff,
even on Linux.
Would that work?
Serial ports certainly are getting scarce! You'd get 2 to a board an
embarrassingly long time ago!
On 05/11/2021 06:10, Darren Freeman wrote:
On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
However, mobos with a serial port are becoming harder to find.
That's not really been my experience, they just moved it to a header.
You will need to supply a DE9 to ribbon cable, say on a bracket, or
installed in a cutout elsewhere in the case.
This is the first one that I checked, and it has such a port labelled
COMA, along the left/bottom edge.
https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
Also note that the Linux PPS driver supports the standard PC parallel
port, which you can usually find as a header. If you are having
performance issues with one, try the other. (But you may need to supply
negative-going edges to the parallel port.)
Have fun,
Darren
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
send an email to time-nuts-leave@lists.febo.com
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There is significant jitter using USB for timing. Has been done poorly for a long time. Well known.
Bill Dailey
Negativity always wins the short game. But positivity wins the long game. - Gary Vaynerchuk
Don’t be easy to understand,
Be impossible to misunderstand
- Steve Sims
On Nov 5, 2021, at 1:33 PM, Andy Talbot andy.g4jnt@gmail.com wrote:
Use FTDI USB serial ports - you can't go wrong with them.
https://ftdichip.com/
I have, at the last count, used something like 200 of their FT232 device in
one form or another on the shack PC. I know that, because device manager
has registered up to COM200. Every time a new one is plugged in, a new COM
port is set up.
Andy
www.g4jnt.com
On Fri, 5 Nov 2021 at 18:26, Alec Teal alec@unifiedmathematics.com wrote:
A friend of mine who lives and breaths this stuff (I wont tell you what
he does - but suffice to say he's authoritative) basically said to me on
something about serial ports that you can't go wrong with USB stuff,
even on Linux.
Would that work?
Serial ports certainly are getting scarce! You'd get 2 to a board an
embarrassingly long time ago!
On 05/11/2021 06:10, Darren Freeman wrote:
On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
However, mobos with a serial port are becoming harder to find.
That's not really been my experience, they just moved it to a header.
You will need to supply a DE9 to ribbon cable, say on a bracket, or
installed in a cutout elsewhere in the case.
This is the first one that I checked, and it has such a port labelled
COMA, along the left/bottom edge.
https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
Also note that the Linux PPS driver supports the standard PC parallel
port, which you can usually find as a header. If you are having
performance issues with one, try the other. (But you may need to supply
negative-going edges to the parallel port.)
Have fun,
Darren
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
send an email to time-nuts-leave@lists.febo.com
To unsubscribe, go to and follow the instructions there.
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Well, yes. No one would rely on a windows PC for timing accuracy, surely
This is what I did to get a fully coherent timing and frequency locked
system for a narrowband LF receiver using an FTDI interface to a PC.
http://g4jnt.com/Coherent_LF_Receiver.pdf
Andy
www.g4jnt.com
On Fri, 5 Nov 2021 at 18:44, Bill Dailey docdailey@gmail.com wrote:
There is significant jitter using USB for timing. Has been done poorly
for a long time. Well known.
Bill Dailey
Negativity always wins the short game. But positivity wins the long game.
- Gary Vaynerchuk
Don’t be easy to understand,
Be impossible to misunderstand
- Steve Sims
On Nov 5, 2021, at 1:33 PM, Andy Talbot andy.g4jnt@gmail.com wrote:
Use FTDI USB serial ports - you can't go wrong with them.
https://ftdichip.com/
I have, at the last count, used something like 200 of their FT232 device
in
one form or another on the shack PC. I know that, because device
manager
has registered up to COM200. Every time a new one is plugged in, a new
COM
port is set up.
Andy
www.g4jnt.com
On Fri, 5 Nov 2021 at 18:26, Alec Teal alec@unifiedmathematics.com
wrote:
A friend of mine who lives and breaths this stuff (I wont tell you what
he does - but suffice to say he's authoritative) basically said to me on
something about serial ports that you can't go wrong with USB stuff,
even on Linux.
Would that work?
Serial ports certainly are getting scarce! You'd get 2 to a board an
embarrassingly long time ago!
On 05/11/2021 06:10, Darren Freeman wrote:
On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
However, mobos with a serial port are becoming harder to find.
That's not really been my experience, they just moved it to a header.
You will need to supply a DE9 to ribbon cable, say on a bracket, or
installed in a cutout elsewhere in the case.
This is the first one that I checked, and it has such a port labelled
COMA, along the left/bottom edge.
https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
Also note that the Linux PPS driver supports the standard PC parallel
port, which you can usually find as a header. If you are having
performance issues with one, try the other. (But you may need to supply
negative-going edges to the parallel port.)
Have fun,
Darren
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
send an email to time-nuts-leave@lists.febo.com
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