On Sep 28, 2005, at 11:09 PM, Wouter van Ooijen wrote:

>> "The IBM PC family represents the height of folly in this
>> [snip mandatory hadshake story]
>
> Strange, I recall programming such serial ports, using just direct
> hardware access, and using 3 wires only. Either that was not on the 
> type
> of PC you describe (in my memory it was, there was little else 
> available
> at that moment), or your text confuses using the bios routines with
> dirtectly using the hardware.
>
I wrote some comm software for the original IBMPC and original serial
port (based on an intel 8250; the NS16450 was ... later.)  The PC bios
was awful.  basica had surprisingly good async support, though.  My
strategy was to to use basica as initialization and for file transfer
and etc, while using ASM for the stuff that had to be fast, like the
H19 terminal emulator and MODEM2 checksum function.  Alas, my code has
no comments about wiring; I do recall the port being unusually picky
about handshaking lines, but I DON'T recall whether that turned out
to be a firmware or hardware issue.

I do know for sure that the first time cisco shipped a router that
didn't have the "flowcontrol" signals looped back (or strapped TRUE),
we got complains of inability to talk to "PCs" very quickly, and had
to do an ECO.  Again, I don't remember whether that turned out to be
a software or hardware issue (it didn't matter.  you pretty much can't
tell a customer "your comm software is broken; get something 
different.")

BillW

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