[time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

[Gary E. Miller]

Yo Ruslan!

On Mon, 13 Feb 2017 11:07:49 -0500
Ruslan Nabioullin <rnabioullin at gmail.com> wrote:

> Hi, generally speaking, what are the performance differences between
> the following: 1. direct RS-232 (i.e., what I believe is a standard
> PCI card offering RS-232---essentially UARTs interfaced more-or-less
> directly to the PCI bus); 2. RS-232 via USB; 3. PPS decoding PCI
> cards (which might also have an IRIG input or even an onboard GNSS
> receiver).

#2 will have a lot higher jitter than #1.  On a #2 you can expect
500 micro second best timing.  On a #1 you can get to 1 micro second.

On a RasPi using GPIO you can get to 500 nano second.  Data
available on request, but better on the devel at ntpsec.org list.

RGDS
GARY
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