30 Oct
2022
30 Oct
'22
5:20 p.m.
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(a)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(a)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(a)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(a)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