On Mon, Nov 11, 2002 at 12:01:09AM -0500, Robertdkeys@aol.com wrote:
> DHV11 sounds good.  I was thinking of setting up
> a serial postscript printer at 1200 baud, and
> that way the handshake would not be required,
> since the printer can buffer at that speed with
> no handshake.

You're kidding, right?  My 11/750 used to happily feed an Apple
LaserWriter -- the original model -- at 4800bps with no handshaking
and no problem.  We eventually switched it to 9600bps and xon/xoff
and that worked great, too.  The printer was on a DHU11 originally --
the DHU does hardware flow control and, IIRC, modem control for the
first four ports, and I'd be surprised if the DHV didn't -- but we
ended up moving it to a DZ11, where it worked fine, too.

The DHU/DHV/CXY are pretty decent serial ports.  Again IIRC the
advantage of the original DH-11 or the Emulex clone thereof (also
available in a Q variant, I think) was that it did both flow and
modem control for all ports.  The DH-11 was a huge multi-slot
assembly, but the Emulex cards are pretty easy to find, and emulate
up to four DH's worth of ports in a single slot.

The really deluxe serial ports for the early VAXen were the DMF/DMZ-32.
Not available in a Qbus variant AFAIK but I've seen them hooked up to
MicroVAXen using Q->U adapters (I was a bit surprised that VAX DMA
worked through one of these, but it wasn't a DEC adapter like the one
on some of the 11/x4 models, either).  However, again IIRC, the 
DH/DHU/DHQ did 38400bps while the DMF/DMZ maxed out at 19200.

The DZ-11 was *intended* to be used with its interrupts routed to a
separate interrupt handling card so it didn't totally hose the VAX
CPU.  This was a common setup for the few VAXen that ran System V,
since they actually had drivers that could do the necessary magic;
BSD didn't.  This at least partially explains why if you bought a
VAX and told DEC you were going to run Unix, you ended up with a
huge pile of DZ-11 serial cards you ended up having to horsetrade
for cards that didn't suck.  And interrupt controller cards that
were just totally useless to you.  But, see, the DEC salesmen
knew that that was what "Unix" wanted for serial ports...

-- 
 Thor Lancelot Simon	                                      tls@rek.tjls.com
   But as he knew no bad language, he had called him all the names of common
 objects that he could think of, and had screamed: "You lamp!  You towel!  You
 plate!" and so on.              --Sigmund Freud