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

[Bob Camp]

Hi

A direct port might be a +/- 100 ns sort of thing most of the time and a +/-10 us 
thing every so often under some OS’s. Most desktop operating systems are not
designed to prioritize random pin interrupts. A dirt cheap MCU coded with a few
(hundred) lines of assembly code may be a better option than a typical desktop. 
Complicating this further is the degree to which some OS’s can be directly or
indirectly optimized. Install *this* package and it all goes nuts. Install that package
 and not much happens ….

Bob

> On Feb 13, 2017, at 11:07 AM, 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).
> 
> Thanks in advance,
> Ruslan
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