All –
I’m working on a simulation project where I’m using two Codex 2121 LDSU (local data service unit) modems to simulate a leased line setup to a DECSYSTEM-2020. These modems use 2-pair cabling (TX+,TX-/RX+.RX-) and DCE DB25 connections. I believe each modem is working in loopback mode, but I can’t get it to work over the 2-pair interface between the modems (i.e., a loop back plug on one modem and terminal on the other). The only manual I’ve been able to locate is the sales brochure, not any kind of user manual.
Anyway, have the interface cross-connected (i.e., TX to RX) but there are no polarity markings so I just used each pair in the same color order.
Has anyone used this kind of modem before, have a manual, or know how to connect them? Thanks!
Rich
--
Rich Cini
http://cini.classiccmp.orghttps://github.com/RichCini
Test ( sorry guys for cluttering , but I'm puzzled since I'm using Hotmail so... should not have this kind of issues )
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Punchcards? You want punchcards? I got punchcards. Not exactly what I think you are looking for but a large sample. Please check out www.punchcardarchive.com
Check the Stats page for a quick summary. Beware the Album page. It takes a while to load. After all, it has to display 25532 cards.
Not a full program but doing a search on CCROS in the Title field will show a few cards that represent a few bits of a read only S/360 program.
Donald
I asked this before a few years ago but didn't come to a firm conclusion. The two parts are shown in this picture: https://rjarratt.wordpress.com/wp-content/uploads/2023/12/img_20231221_1123…
They are from a VT100 Monitor board. There is no schematic for my version of the board, but a related schematic is on p58 of this schematic: https://bitsavers.org/pdf/dec/terminal/vt100/MP00633_VT100_Schematic_Feb82.…. They are labelled Q414 and CR406, but the Feb 82 revision uses a different board and those two parts are in TO-220 packages rather than TO-3 as here..
I have removed both of them and tested them with a DMM. Neither of them measure as two diodes, they do not measure open circuit in any direction, so either they are both faulty or they are not transistors (unlikely). I have found a spec for a 2SB411 at https://alltransistors.com/transistor.php?transistor=10279. This seems to be a germanium transistor. When I last asked about this I had a conversation with Tony Duell, who was very sceptical that these could be germanium transistors, so naturally I am very doubtful that they are 2SB411 transistors. However, in the schematic Q414 is shown as NPN, the 2SB411 is PNP and this seems to match the way the part is connected on my board (Collector to HORIZ GND). I am working on a reverse engineered schematic.
Can anyone tell me what these components are so I can find a datasheet for them? Better still a suggested replacement would be really helpful, especially if they are 2SB411s because they seem to be hard to find.
Thanks
Rob
Nice, Jay! Thank you
> On Feb 22, 2026, at 18:44, Jay Jaeger <cube1(a)charter.net> wrote:
>
> On 2/21/2026 9:27 AM, Jacob Ritorto via cctalk wrote:
>> Hiya.
>> Is DECnet for RT-11 still lost? If not, anyone got a link to it?
>> thx
>> jake
>
> I may have *SOME* of it. I have three RX50's and one RX02 that have some DECNet RT V2.1 files. They are NOT distribution disks, and the disks have hand-written labels, so they might not even contain what the handwritten label indicates - I have not checked them out under SimH.
>
> Anyway, I just put them in my "bitsavers contribution" area of my Google Drive, and they can be found on my Google Drive at:
>
> https://drive.google.com/drive/folders/1fiOScGSpvLiVQ0yyOg2yC5EpqRKiKWQ5?us…
>
> JRJ
Hello,
I'm an employee with the National radio astronomy observatory here in Socorro New Mexico.
As part of our NGVLA upgrades, we are seeking to get rid of old data tapes from the tape reel days of Computing. These contain things such as the boot loaders, OS, specific collection programs and antenna movement programs.
I personally would hate to see these just wind up in the literal dumpster and would like to see them sent out to a museum or an archiving body that can preserve them and keep them safe as a dynamic part of history.
If anyone is interested or knows someone who would be interested in the VLAs data tape library please let me know.
V/R
Danielle Werts
Front end engineer
VLA Socorro New Mexico
I've started working on a disassembly of the Digital VT320 video
terminal, so I'm diving into 8051 assembler.
At the moment, I'm using the D52 disassembler and am getting decent
results, although I wished I hadn't used the analyse option to produce
a starting control file; it doesn't cope at all well with code
involving lots of jump tables because the control flow appears to
break, and it decides that much of the code is just data. Ho hum.
Nevertheless, the code looks pretty understandable at the moment, so
the next stage is to annotate by hand, instead of updating the control
file, and to assemble whenever I make a change so that I can be sure
that I can produce the original ROM.
There isn't an "A52" to match D52, so I was wondering if anyone has
recommendations for a FOSS macro assembler that will take D52's output.
I ask for a macro assembler because there are some modifications I'd
like to make to the source file to clear things up. One of these would
be to cope with the fact that DEC decided that all of their jump tables
would have addresses in little-endian format, despite the 8051 being a
big-endian device. So, the normal "dw" directive is not going to work
for me, and I'll need to do something like:
dwl macro %1
db low(%1), high(%1)
endm
(Totally pulling that syntax out of my bum, btw.)
A quick search finds as31 and naken_asm - anyone use these?
I'd also love to hear recommendations for emulator code for the 8051,
preferably simple C because I'm going to need to hook up a 2681
DUART, 5911 EEPROM and DC7081 video chip (all presumably new code) to
get this working.
Paul.
On 2/21/26 07:48, emanuel stiebler wrote:
> Everex had their own Unix version (5.4?), "ESIX" which ran on intel.
> Probably they ran that?
No, it ran SCO Unix, which was the business version popular at the time.
I found the ad and edition of computerworld in the Internet Archive: The
issue is the June 22nd 1992 one and it has all sorts of interesting
articles and predictions from people like Gates, Jobs, Wang, Bell, and
others. Going to be worth a read here.
Anyway, on the PDF download it starts at page 186-189.
They benchmarked it against a Dec 433MP (could also do 6 processors) and
a SystemPro (2) with 60 user loads. Wow.
A buddy of mine showed off his Wyse 520 and was wondering if anyone on here
has one and if you use it. It's a nice looking keyboard but I'm not that
fond of the small screen.
Daniel
sysop | Air & Wave BBS
finger | calcmandan(a)bbs.erb.pw
