Well, for incoming traffic DHV11's had things like pretty deep buffers,
I wonder if it was smart enough to see a bunch of characters coming in
then buffer them for a single DMA hit on the CPU. Maybe if a character
came in and nothing else it could do an interrupt but usually things
were chatty enough that it probably was able to batch the inputs into a
single DMA transfer.
The real value of DMA was in output (you could sent a whole chunk of
data back in one shot) and of course file transfers and the like. A DZ11
would pound the CPU into snot with endless interrupts and each character
out had to be done as well.
The reason I have so many is because I believe these were used with a
COMM-IO-P system. This was a Dec custom thing that would use an on-board
processor to poll a bunch of DZ11's and format the data nicely for the
CPU. I think the DZ11's were polled as opposed to interrupted so it
could handle a lot of well formatted traffic.
The really fun stuff is that I found the manuals for the Associated
Computer Consultants (ACC) IF-11/3780 modules. These are interesting:
They are a full length Unibus card that can handle 2 serial lines.
However the card has Z80 CPUs and other stuff to handle the full
2780/3780 communications for up to 2 different IBM mainframes.
ASCII-EBCDIC: Yep, it did this.
Space Compression/Expansion? Yep.
Vertical and Horozontal format control? Sure!
Automatic retransmission and error correction
BISYNC protocol with proper blocking and block checks. Yep, that too...
Beast of a card, I think that one of them was also able to be a full
X.25 PAD.
On 10/30/2022 2:58 PM, Nigel Johnson Ham via cctalk wrote:
and typing long sentences to take advantage of the NPR burst after the
initial interrupt!
Nigel Johnson, MSc., MIEEE, MCSE VE3ID/G4AJQ/VA3MCU
Amateur Radio, the origin of the open-source concept!
Skype: TILBURY2591
On 2022-10-30 14:49, Wayne S via cctalk wrote:
The difference between dz and dh interfaces is that the dh used dma
instead of interrupts to get characters to the cpu. It would be
transparent to any software.
I did a write up on them 40 years ago justifying the replacement of a
dz with dh saying that decreasing interrupts would increase
performance on my VAX 780. It did, but just a bit. To make a big
difference, you’d have to have a LOT of people banging away on serial
terminals and rs-232 connected printers.
Sent from my iPhone
On Oct 30, 2022, at 09:22, Jay Jaeger via cctalk
<cctalk@classiccmp.org> wrote:
For an awful lot of software, holding a line until there is an end
of line is not practical. Text editors in particular simply won’t
work that way. The UNIX shell wouldn’t work in that environment
either. So this character by character interrupt is pretty standard.
Sent from my iPhone
On Oct 29, 2022, at 8:02 PM, Nigel Johnson Ham via cctalk
<cctalk@classiccmp.org> wrote:
The performance of the DZ11 is not good. It did an interrupt for
every character, just like a DL11. The Able DMAXes blocked until a
carriage return and then did a DNA, IIRC.
Not sure about the DH and DHV11 - its been a long time. We used
Able DMAXes on the Canadian NAPLPS system, named Telidon, but that
was back in the 1200/300 baud days!
However for vintage computer purposes, that's probably not a concern.
cheers,
Nigel
Nigel Johnson, MSc., MIEEE, MCSE VE3ID/G4AJQ/VA3MCU
Amateur Radio, the origin of the open-source concept!
Skype: TILBURY2591
On 2022-10-29 14:37, Tony Duell via cctalk wrote:
On Sat, Oct 29, 2022 at 6:14 PM Bill Degnan via cctalk
<cctalk@classiccmp.org> wrote:
Being lazy admittedly but can these be used for single serial
interfacing?
They will not emulate a DL11 or any similar single serial port.
You don't have to use all 8 ports on the DZ11 card but you still need
the right software driver.
That said,it would be a pity to scrap these. Surely all Unibus cards
are getting hard to find now.
-tony
Bill
On Sat, Oct 29, 2022, 11:01 AM Chris Zach via
cctalk<cctalk@classiccmp.org>
wrote:
I have a box here of 14 DZ11 Unibus 8 line serial port
interfaces. And I
have no clue why I have them.
Anyone need some? Otherwise I'll Ebay/recycle them.
CZ
