No, just the protocal the mac uses to transfer on the serial line, the pins,
the handshaking, etc. PCs use rs-232 and macs use rs-422. rs-422 is a twisted
pair version of rs-232 that is tremendously faster. However, to connect an
rs-232 to a rs-422 requires a common ground and some nasty klunking, and in
the process you end up with a much slower connection (115200bps maybe) and
a few missing signals, most noteably RTS, request to send, which asks the
other end to stop sending either so the recieve buffers can be emptied or
data can be sent. Anyhow, this problem can be avoided by using DTR in lieu
of RTS. The moral of the story is that PCs suck and macs rule.

On Thu, Jul 26, 2001 at 05:46:43PM -0700, Henry B. Hotz wrote:
> At 7:21 PM -0500 7/26/01, Phil Frost wrote:
> >I don't know about bsd, but linux the serial driver can use DTR/CTS flow
> >control instead of the usual RTS/CTS. This is usefull only when using the
> >serial port in rs-232 mode (that's what pcs and most modems use). When
> >doing a mac<->mac connection rs-232 isn't used. I don't recall the name of
> >the serial protocall mac uses, but I do know it uses twisted pair and is much,
> >much faster.
> 
> I think you are talking about LocalTalk.  That's a CSMA/CD usage of 
> the port (like Ethernet) that runs at 230kbits/second.  Not supported 
> by NetBSD at this time.