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

[Ruslan Nabioullin]

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