29 Jan
2014
29 Jan
'14
2:51 p.m.
On 2014-01-29 10:00, Kyle Owen<kylevowen at gmail.com> wrote:
Eh? What? There was an option for 8-bit clean communication in the
ASR33, as well as other parity choices. But by default an ASR33 have
*MARK* parity.
And all older PDP-8 software that I've ever seen also assumes MARK
parity. If you try running older PDP-8 software with your terminal set
to even parity, it will not work.
If you are ever near an ASR33 with a paper punch, you can easily verify
that it is doing mark parity by just enabling the punch, and check what
codes you get there as you type, with the ASR33 in local mode.
Johnny
>
>I don't remember ever seeing a Model 33 with parity. And weren't
>telegrams sent in 5 level code? If not at the end, then surely before
>ASCII appeared. And of course before either, there was Morse code, which
>doesn't come with parity either.
>
>All parity can do is convert garbled characters into missing characters.
> Neither is good. Telegraph operators probably relied on having good
>signal quality, ensuring adequate bit error rate values, at which point
>parity is not particularly needed. And with Morse, you're probably relying
>on skilled operators -- ECC performed by trained brain cells.
Wikipedia seems to indicate that the Model 33 ASR sent 7-bit ASCII with
even parity. I've found that in many of the programs on my PDP-8/E, even
parity is required, which I presume stems from the Model 33 ASR days. 
29 Jan
29 Jan
3:20 p.m.
On Wed, Jan 29, 2014 at 1:51 PM, Johnny Billquist <bqt at update.uu.se> wrote:
Eh? What? There was an option for 8-bit clean communication in the ASR33,
as well as other parity choices. But by default an ASR33 have *MARK* parity.
And all older PDP-8 software that I've ever seen also assumes MARK parity.
If you try running older PDP-8 software with your terminal set to even
parity, it will not work.
If you are ever near an ASR33 with a paper punch, you can easily verify
that it is doing mark parity by just enabling the punch, and check what
codes you get there as you type, with the ASR33 in local mode.
Johnny
I punched this tape on a Model 33 ASR in local mode and it seems to have
even parity. Bonus points for deciphering it! :)
http://i.imgur.com/R3GPWIS.jpg
I'll try some more software with mark parity, but I believe CHECKMO II (the
chess game) really wants even parity.
Kyle
4:05 p.m.
On Jan 29, 2014, at 11:51 , Johnny Billquist <bqt at update.uu.se> wrote:
And all older PDP-8 software that I've ever seen
also assumes MARK parity. If you try running older PDP-8 software with your terminal set
to even parity, it will not work.
Thank you! That is good to know. My recently-acquired ASR 33 has a mark parity keyboard,
and I have been wondering whether that was a preferred configuration for use with some
future PDP-8 that I don't have yet.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
6:54 p.m.
All parity can do is convert garbled characters into
missing characters.
If you are sitting there reading text interactively, a garbled character
is no big deal, and you can ignore it/interpolate what the correct one
should be, and not care.
But, there can exist situations where KNOWING that a character is wrong is
more important, perhaps enough so that you would rather repeat the entire
transmission until you get a copy with no errors.
Likewise, "all parity memory does is make the whole PC freeze up [when a
memory error occurs] while you are trying to get important work done"
(while printing the payroll?)
Would you rather continue, unaware that an error has occured? Or have to
redo the task?
Admittedly, I think that the "recovery" options of the parity handling of
the 5150 were grossly inadequate. Consider Brett Salter's "Periscope", or
even the freeware NMIEXIT.COM
But, IBM felt strongly that they would rather face complaints about
computer stopping and not getting results, than complaints about it
producing WRONG results.
OTOH, many people would rather IGNORE all errors. Central Point's
PCTools, in order to avoid the "absolutely intolerable" situation of
disruption of their pretty screen displays by disk error messages,
intercepted the critical error vector, and changed ALL errors to an
automatic response of "IGNORE"! I found THAT out when I realized that the
disk retries that seemed to resolve, and never produced an error message
were actually loss of sector(s) of my "INCOMING ORDERS TELEPHONE LOG"
file! I immediately switched that text editing back to PC-Write.
--
Grumpy Ol' Fred cisin at xenosoft.com
8:27 p.m.
On 29 January 2014 23:54, Fred Cisin <cisin at xenosoft.com> wrote:
Central Point's
PCTools, in order to avoid the "absolutely intolerable" situation of
disruption of their pretty screen displays by disk error messages,
intercepted the critical error vector, and changed ALL errors to an
automatic response of "IGNORE"! I found THAT out when I realized that the
disk retries that seemed to resolve, and never produced an error message
were actually loss of sector(s) of my "INCOMING ORDERS TELEPHONE LOG"
file! I immediately switched that text editing back to PC-Write.
That is pretty scary, but I'm curious. Back in the day - late 1980s -
I used PC Tools heavily. It was one of my go-to, er, well, tools for
data recovery, disk defragging, rapid backup to floppy, etc.
But that's all it did. It was a utilities toolkit.
What were you using it for? It had no productivity apps that I recall...
--
Liam Proven * Profile: http://lproven.livejournal.com/profile
Email: lproven at cix.co.uk * GMail/G+/Twitter/Flickr/Facebook: lproven
MSN: lproven at hotmail.com * Skype/AIM/Yahoo/LinkedIn: liamproven
Tel: +44 20-8685-0498 * Cell: +44 7939-087884
8:50 p.m.
> PCTools, in order to avoid the "absolutely
intolerable" situation of
On Thu, 30 Jan 2014, Liam Proven wrote:
That is pretty scary, but I'm curious. Back in the
day - late 1980s -
I used PC Tools heavily. It was one of my go-to, er, well, tools for
data recovery, disk defragging, rapid backup to floppy, etc.
But that's all it did. It was a utilities toolkit.
What were you using it for? It had no productivity apps that I recall...
"PC Desktop"?? within it.
TSR text editor, and other "accessory" programs.
Did they drop those from later PCTools?
It provided some simple basic task switching for DOS, without the extreme
overhead of Windoze.
Until I ran into the disabled critical error handler, it was doing OK.
10:40 p.m.
On 30 January 2014 01:50, Fred Cisin <cisin at xenosoft.com> wrote:
"PC Desktop"?? within it.
TSR text editor, and other "accessory" programs.
Did they drop those from later PCTools?
It provided some simple basic task switching for DOS, without the extreme
overhead of Windoze.
Until I ran into the disabled critical error handler, it was doing OK.
Oh, OK. I don't think I ever saw that. My big speciality in the DOS
days was memory optimisation - wringing every last byte of
conventional RAM out of a 386. I tended to avoid TSRs - they were
memory hogs. I used DesqView, Windows 2 or Concurrent DOS if I really
needed multiple tasks.
--
Liam Proven * Profile: http://lproven.livejournal.com/profile
Email: lproven at cix.co.uk * GMail/G+/Twitter/Flickr/Facebook: lproven
MSN: lproven at hotmail.com * Skype/AIM/Yahoo/LinkedIn: liamproven
Tel: +44 20-8685-0498 * Cell: +44 7939-087884
8:44 p.m.
On Jan 29, 2014, at 6:54 PM, Fred Cisin <cisin at xenosoft.com> wrote:
True. Until you get a double bit error, of course. And that requires parity errors to
produce a distinctive error indication, as opposed to simply causing the character to be
ignored. I don?t know what old style printing terminals did. (It sounds like the ASR33
never did parity on receive.) What you describe did appear in the PLATO terminals, which
indeed had a crude NAK and retransmit scheme that helped with modest link error rates.
paul
All parity can
do is convert garbled characters into missing characters.
If you are sitting there reading text interactively, a garbled character
is no big deal, and you can ignore it/interpolate what the correct one
should be, and not care.
But, there can exist situations where KNOWING that a character is wrong is
more important, perhaps enough so that you would rather repeat the entire
transmission until you get a copy with no errors. 
30 Jan
30 Jan
11:35 a.m.
I punched this tape on a Model 33 ASR in local mode and it seems to have
even parity. Bonus points for deciphering it!:)
http://i.imgur.com/R3GPWIS.jpg
Guessing the bit layout and assuming ASCII characters, I got:
"THIS IS A TEST OF THIS COOL TELETYPE. WELCOME TO"
Do I get the bonus points :-)
(I didn't see any parity errors, or any hanging chad!)
Regards,
Peter Coghlan.
3:09 p.m.
Eh? What? There was an option for 8-bit clean
communication in the
ASR33, as well as other parity choices. But by default an ASR33 have
*MARK* parity.
I am not sure what you mean by '8 bit clean' here.
As far as I know :
Every ASR33 punch and reader are 8-bit clean in that the former wil
lpunch the 8 incoming bits, the latter reds the 8 data tracks on the tape
and sends them unchanged.
Every ASR33 -- in fact every Model 33 -- typing unit ignores the 8th bit.
There are 2 versions of the keyboard. One does Mark partiy, the other
Even parity, I don;t think, for example, Odd parity was ever available.
-tony
4:18 p.m.
On Jan 30, 2014, at 3:09 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I'm pretty sure that's what was meant; the ASR33 will receive and
send 8-bit tape sequences unmolested. Thus "clean", as opposed
to what would happen if it tried to interpret either side as 7-bit
with or without parity.
- Dave
Eh? What?
There was an option for 8-bit clean communication in the
ASR33, as well as other parity choices. But by default an ASR33 have
*MARK* parity.
I am not sure what you mean by '8 bit clean' here.
As far as I know :
Every ASR33 punch and reader are 8-bit clean in that the former wil
lpunch the 8 incoming bits, the latter reds the 8 data tracks on the tape
and sends them unchanged.
31 Jan
31 Jan
5:30 p.m.
On Jan 30, 2014, at 3:09 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I'm pretty sure that's what was meant; the ASR33 will receive and
send 8-bit tape sequences unmolested. Thus "clean", as opposed
Sure. My confusion comes from the word 'option;. As far as I know, all
ASR33s do this, it cannot be disabled, there is no option to add
automatic parity generation/checking to the paper tape punch or reader,
etc.
-tony
Eh? What?
There was an option for 8-bit clean communication in the
ASR33, as well as other parity choices. But by default an ASR33 have
*MARK* parity.
I am not sure what you mean by '8 bit clean' here.
As far as I know :
Every ASR33 punch and reader are 8-bit clean in that the former wil
lpunch the 8 incoming bits, the latter reds the 8 data tracks on the tape
and sends them unchanged.
3831
days inactive
3832
days old
11 comments
9 participants
participants (9)
-
ard＠p850ug1.demon.co.uk -
bqt＠update.uu.se -
cctech＠beyondthepale.ie -
cisin＠xenosoft.com -
fraveydank＠gmail.com -
kylevowen＠gmail.com -
lproven＠gmail.com -
nf6x＠nf6x.net -
paulkoning＠comcast.net