Info needed on Dec DHU11 communication board

[Jim McKie]

In article <237 at spock.UUCP> overlord at spock.UUCP (Rick Link '85 off) writes:
    
    	Is anyone out there using one of the Dec DHU11 communication
    boards?  How is it working. I am considering purchasing one from Dec,
    and would be delighted to hear any comments from other systems that use
    them.  Are there any strange complications or service problems?

Yes, 4.3BSD comes with a DHU11 driver, written by Dave Johnson at Brown.
It is a 16-line async multiplexer like the DH11 (single board like the
Able DH/DM), with useable speeds up to 19.2K (it has 38.4K, but you can't
mix all the speeds due to hardware implementation using DUARTS). It has DMA
or a FIFO on output, but with only correct abort of a transmission in DMA
mode. The receiver interrupt can be programmably delayed by 2-255 milli-
seconds, giving reduced interrupt load without requiring the usual software
timer routine . It has full modem control, and a per-line bit to set saying 
'interrupt when the modem signals change', neat for 'softCAR' lines (this 
isn't used in the 4.3BSD driver). There is also hardware support for auto
 XON/XOFF on both input and output, but, again, this isn't currently used.

The painful thing about it is that it has its own special distribution panel
requiring 4 40-pin berg connectors from the board to the panel. To those of 
us who like to put the distribution panels in the back of a Micom, and are
used to (and planned for) running 2 50-pin berg cables, just like the DH/DM,
DZ11, etc, this is a problem.
   
    	Also, just how complicated is it to add supplementary memory to
    a Vax 11/750 running UNIX. Do I have to make modifications to the kernal
    to utilize the new memory, or does the system take care of these things
    for me?
The kernel takes care of those things for you.

Jim McKie	Centrum voor Wiskunde en Informatica, Amsterdam
mcvax!jim