Hi there,
I have a Memodyne M-80 Digital Cassette 'Computer' which, in talking to
people more experienced than me, seems to be just a digital cassette
recorder. Googling around there seems to be very little info out there,
although one paper written about their use with scientific equipment
detailed some of the bits triggered to make the recorder operate. Mine has
several cards including a Z80 CPU card and serial input/output.
I was wondering if anyone out there was familiar with these and/or had a
manual? I read these were even used sometimes with SWTPC
terminals/computers, so I'd be interested to see if I can get it running.
Thanks!!
Brad
> From: Diane Bruce
> PL/M wasn't bad either.
I forgot about PL/M...
> Telephone companies preferred deterministic behaviour from their code
> and operating systems.
Not just telco's. Many (most?) people doing stand-alone applications want
this, or something close to it.
> There are many warts in C I would remove if I had the power to. ;)
Eh, don't we all.
My favourite peeve: in cloning BCPL, they left out 'valof/resultis'. That
made certain kinds of macros really, really ugly...
> C is a high level PDP-11 assembler to this day. (auto increment and
> decrement)
This myth persists, but it's wrong. B (the typeless predecessor to C) on the
PDP-7 had them, before the PDP-11 existed, as DMR attests:
People often guess that they were created to use the auto-increment and
auto-decrement address modes provided by the DEC PDP-11 on which C and Unix
first became popular. This is historically impossible, since there was no
PDP-11 when B was developed.
The document that's excerted from:
http://www.bell-labs.com/usr/dmr/www/chist.html
might be of interest here, since it contains a section ("Whence Success?")
containing his take on why C was a success (e.g. "it evidently satisfied a
need for a system implementation language efficient enough to displace
assembly language, yet sufficiently abstract and fluent to describe
algorithms and interactions in a wide variety of environments").
Noel
Oh, another factor that led to success for C, I suspect: I/O is not in the
language, it's handled by optional subroutine libraries. This made it very
easy for compilers/etc to produce language for stand-alone systems. Compare
PL/I, which needed a large subroutine library to run on bare hardware.
> From: Paul Koning
> Algol 68 has both pointers and structures.
Yeah, but Algol-68 never did much (although it had a certain amount of
influence). Why, I'm not certain - I suspect the fact that it was fairly
complex had something to do with it, but I expect its biggest problem was
that a number of _very_ respectd people from its committee denounced it
roundly (whether their reasons were good or bad, I can't say).
Tony Hoare's Turing lecture, "The Emperor's Old Clothes", recounts a lot of
that. (That's the source of the famous quote about "there are two ways of
constructing a software design: One way is to make it so simple that there
are obviously no deficiencies and the other way is to make it so complicated
that there are no obvious deficiencies." He was talking about Algol-68,
there.)
> So does Pascal.
Which didn't have a lot of the capabilities needed to be system language at
_that point in time_ (remember, this is about 'why did C succeed, back then');
it was, after all, originally designed as a pedagogical language.
> And Modula.
That was late 70's - C was already off and running by then.
> The main thing C has that most other languages don't is *unsafe* data
> typing - the ability to subvert the type system at the drop of a cast,
> and the programming tradition to do this a lot.
{Sighs.} You really seem to have it out for C. You'll never be able to
understand why it was so successful if you start out with the mindset that
it's total crap (even if that's not the way you thought you meant that
comment). That _is_ the implication of that "the main thing that C has"
comment - compared to things available _at the time_, like BCPL, etc, it _did_
have significant advantages.
Does it have issues? Sure. But the main reason it was so successful is that
compared to the other alternatives available _at the time_, it was, overall,
a better mouse-trap. (It wasn't just that it went with Unix - as DMR pointed
out, below, it succeeded in a lot of places that Unix didn't.)
> But it was cheap, available, and good enough to do useful work.
There's a lot of truth to that. Dennis Ritchie's HOPL presentation, "Five
Little Languages and How They Grew":
http://www.bell-labs.com/usr/dmr/www/hopl.html
has a section at the end about "how C succeeded in becoming so widely used",
and it's close to that. Some may consider your description a put-down; DMR I
expect would embrace it.
> I think the answer is simpler: Unix was adopted by a number of academic
> groups because it was available on easy terms
That certainly didn't hurt, but I don't think it was the biggest factor, by a
long way.
I think one of the biggest things is that early Unix (I'm thinking V6, V7)
was a system with an incredibly high bang/buck ratio - for the size, one got
a heck of a lot of functionality. This was important not just for _use_, for
for pedagogical reasons - to give students an example of a well-done system.
The fact that the hardware it ran on (PDP-11's) was modestly priced (for the
day) also helped a lot.
> and it was adopted by a very successful company (Sun)
Unix had taken off big-time before Sun even appeared.
Noel
On 10 May 2016 at 03:12, Eric Christopherson <echristopherson at gmail.com> wrote:
> Gmail always tells me COURYHOUSE's messages would have been treated as
> spam, if I hadn't specifically exempted the messages of this list from ever
> being blocked. I wonder if Google has a prejudice against aol.com
> addresses? :)
No, it's a problem caused by the mailing list, yahoo (and presumably
aol as well) use an authentication system to let recipients validate
that the email is legit. That doesn't work properly with many standard
mailing lists. Google 'dmarc yahoo mailing list', for example.
nope it is working
In a message dated 4/27/2016 10:48:48 P.M. Mountain Standard Time,
dkelvey at hotmail.com writes:
Has the list gone down or just dropped me again?
Hi guys,
I have a Memodyne M80 'Cassette Computer'. From what I've gathered, it's
basically just a digital tape drive (it has about 5 boards in it, including
a Z80 board with an emprom marked '1200 baud', although from one sales doc
it looks like it could have been built out to be a 'general purpose' Z80
computer. I've read these were used for a variety of purposes including
SWTPC terminals like mine.
What I cannot find though is any actual instruction manuals, etc that
explain how to use it. I did find one PDF online as part of a university
paper that described another Memodyne's system a little bit.
Wondering if anyone has any info out there. It's a neat little box to look
at, anyway.
Many thanks, esp. to those like Chuck who were able to offer some useful
advice thus far on it! :)
Brad
Hi guys,
I have a Memodyne M80 'Cassette Computer'. From what I've gathered, it's
basically just a digital tape drive (it has about 5 boards in it, including
a Z80 board with an emprom marked '1200 baud', although from one sales doc
it looks like it could have been built out to be a 'general purpose' Z80
computer. I've read these were used for a variety of purposes including
SWTPC terminals like mine.
What I cannot find though is any actual instruction manuals, etc that
explain how to use it. I did find one PDF online as part of a university
paper that described another Memodyne's system a little bit.
Wondering if anyone has any info out there. It's a neat little box to look
at, anyway.
Many thanks, esp. to those like Chuck who were able to offer some useful
advice thus far on it! :)
Brad
Hi,
I have an InterSystems DPS-1 chassis in pretty good condition
coming my way and I'd like to put an IA-2000 CPU in it. Anybody
have one they might consider selling?
Thanks,
Bill S.
Hi, all. It's been a while since I've discussed anything here. We've made
a lot of progress re-constructing a couple of Point 4 machines (as much as
one can without the actual hardware), yet still need some help from a few
knowledgeable folks in this 35+ year old OS. It was built on the DG Nova
foundation, but made by Educational Data Systems, which became Point 4, for
their Point 4 machines. So, it doesn't exactly "just run" on SimH Nova.
We've been in regular contact with Bruce Ray, who is a true expert in all
Data General and related systems. He has already helped us TREMENDOUSLY.
http://NovasAreForever.org
But other than Bruce Ray, are there any other folks here on this forum who
may have had any IRIS programming, either on the Point 4, or another system
of similarity in the late '70s to early '80s?
I've hunted down a handful of people so far on LinkedIn and scouring the
internet, and only a few of those have responded. But I just thought I'd
make a shout out here. A small handful have kindly responded, with either
limited recollection or availability, or both.
In addition to Bruce, those who have contributed so far include David
Takle, and one of the original Point 4 IRIS designers, Dan Paymar.
We've added a LOT of new content and progress to our
restoration/re-creation of what is turning out to be TWO distinct Point 4
IRIS systems.
Stop by our site if you like, and especially review the directory page
"Understranding IRIS":
http://microtechm1.blogspot.com/p/understanding-iris.html
Does anyone here have anything to add, or IRIS/Point 4 documentation that
could be helpful here (other than what we have at
http://microtechm1.blogspot.com/p/manuals.html ).
Thanks all, I always appreciate the fantastic feedback here.
-AJ
http://MightyFrame.comhttp://MicrotechM1.blogspot.com
