From lm at mcvoy.com Sat Apr 3 03:54:18 2021 From: lm at mcvoy.com (Larry McVoy) Date: Fri, 2 Apr 2021 10:54:18 -0700 Subject: [COFF] [TUHS] Zombified SCO comes back from the dead, brings trial back to life against IBM In-Reply-To: References: <20210401145025.GA1202@naleco.com> <20210402161147.GG8268@mcvoy.com> Message-ID: <20210402175418.GH8268@mcvoy.com> On Fri, Apr 02, 2021 at 01:50:12PM -0400, Theodore Ts'o wrote: > On Fri, Apr 02, 2021 at 09:11:47AM -0700, Larry McVoy wrote: > > > Long before Linus released Linux into the wild in 1990 for the >>386<< much > > > less any other ISA, IBM had been shipping as a product AIX/370 (and AIX/PS2 > > > for the 386); which we developed at Locus for them. The user-space was > > > mostly System V, the kernel was based on BSD (4.1 originally) pluis a great > > > deal of customization, including of course the Locus OS work, which IBM > > > called TCF - the transparent computing facility. It was very cool you > > > could cluster 370s and PS/2 and from >>any<< node run a program of either > > > ISA. It has been well discussed in this forum, previously. > > > > It's really a shame that TCF didn't get more widespread usage/traction. > > That's exactly what BitMover wanted to do, I wanted to scale small cheap > > SMPs in a cluster with a TCF layer on it. I gave some talks about it, > > it obviously went nowhere but might have if we had TCF as a starting > > point. TCF was cool. > > (Moving this to COFF...) > > Out of curiousity, how was TCF different or similar to Mosix? The thing I remember most about TCF is that it virtualized struct proc, so process pointers were like vnodes and you could move a process to a different node in the cluster and ps still saw it and could dig info out of the remote kernel. From tytso at mit.edu Sat Apr 3 03:50:12 2021 From: tytso at mit.edu (Theodore Ts'o) Date: Fri, 2 Apr 2021 13:50:12 -0400 Subject: [COFF] [TUHS] Zombified SCO comes back from the dead, brings trial back to life against IBM In-Reply-To: <20210402161147.GG8268@mcvoy.com> References: <20210401145025.GA1202@naleco.com> <20210402161147.GG8268@mcvoy.com> Message-ID: On Fri, Apr 02, 2021 at 09:11:47AM -0700, Larry McVoy wrote: > > Long before Linus released Linux into the wild in 1990 for the >>386<< much > > less any other ISA, IBM had been shipping as a product AIX/370 (and AIX/PS2 > > for the 386); which we developed at Locus for them. The user-space was > > mostly System V, the kernel was based on BSD (4.1 originally) pluis a great > > deal of customization, including of course the Locus OS work, which IBM > > called TCF - the transparent computing facility. It was very cool you > > could cluster 370s and PS/2 and from >>any<< node run a program of either > > ISA. It has been well discussed in this forum, previously. > > It's really a shame that TCF didn't get more widespread usage/traction. > That's exactly what BitMover wanted to do, I wanted to scale small cheap > SMPs in a cluster with a TCF layer on it. I gave some talks about it, > it obviously went nowhere but might have if we had TCF as a starting > point. TCF was cool. (Moving this to COFF...) Out of curiousity, how was TCF different or similar to Mosix? - Ted From clemc at ccc.com Sat Apr 3 05:04:22 2021 From: clemc at ccc.com (Clem Cole) Date: Fri, 2 Apr 2021 15:04:22 -0400 Subject: [COFF] how was TCF different or similar to Mosix Message-ID: On Fri, Apr 2, 2021 at 1:50 PM Theodore Ts'o wrote: > Out of curiousity, how was TCF different or similar to Mosix? > Many similar ideas. TCF was basically the commercial implementation of the Locus, which Jerry and students built at UCLA (one 11/70s original). I want to say the Locus papers are in some early SOSPs. MOSIX was its own Unix-like OS, as was Locus [and some of this was in Sprite too BTW]. TCF was a huge number of rewrites to BSD and was UNIX. The local/remote restructuring was ad-hoc. By the time Roman and I lead TNF, we had created a formal VPROC layer as an analog to the VFS layer (more in a minute). TNC was to be the gut of Intel's Paragon using OSF/1 as base OS. The basic idea of all of them is that the cluster is looks like a single protection domain with nodes contributing resources. A Larry says a ps is cluster-wide. TCF had the idea of features that each node provides (ISA, floating-point unit, AP, *etc*..) so if a process needed specific resources, it would only run on a node that had those resources. But it also meant that processes could be migrated from a node that had the same resources. One of the coolest demos I ever saw was we took a new unconfigured PS/2 at a trade show and connected the ethernet to it on the trade show network, and put in a boot floppy. We dialed back into a system at an LCC, and filled in some security things, details like the IP address of the new system and soon it booted and joined the cluster. It immediately started to add services to the cluster, we walked away, and (overnight) the system had set up the hard disk and started caching locally things that were needed for speed. Later I was editing a file and from another screen migrated the process around the cluster while the editing was active. The problem with VPROC (like VFS) is it takes surgery all over the kernel. In fact, for Linux 2.x kernel the OpenSSI folks did all the kernel work to virtualize the concept of process, which sadly never got picked up as the kernel.org folks did not like it (a real shame IMO). BTW, one of the neat side effects of a layer like VPROC is things like checkpoint/restart are free -- you are just migrating a process to the storage instead of an active processor. Anyway, Mosix has a lot of the same types of ideas. I have much less experience with it directly. -------------- next part -------------- An HTML attachment was scrubbed... URL: From sauer at technologists.com Sat Apr 3 06:09:46 2021 From: sauer at technologists.com (Charles H Sauer) Date: Fri, 2 Apr 2021 15:09:46 -0500 Subject: [COFF] how was TCF different or similar to Mosix In-Reply-To: References: Message-ID: <34c3d7a6-350b-36ac-d84c-340b9024e55e@technologists.com> Amazon still carries the Popek/Walker LOCUS book https://smile.amazon.com/Distributed-System-Architecture-Computer-Systems/dp/0262517191/ I haven't cracked it open in years, but I assume it is still the best starting point. On 4/2/2021 2:04 PM, Clem Cole wrote: > On Fri, Apr 2, 2021 at 1:50 PM Theodore Ts'o > wrote: > > Out of curiousity, how was TCF different or similar to Mosix? > > Many similar ideas.  TCF was basically the commercial implementation of > the Locus, which Jerry and students built at UCLA (one 11/70s > original).  I want to say the Locus papers are in some early SOSPs. > > MOSIX was its own Unix-like OS, as was Locus [and some of this was in > Sprite too BTW].  TCF was a huge number of rewrites to BSD and was > UNIX.  The local/remote restructuring was ad-hoc.   By the time Roman > and I lead TNF, we had created a formal VPROC layer as an analog to the > VFS  layer (more in a minute). TNC was to be thegut of Intel's Paragon > using OSF/1 as base OS. > > The basic idea of all of them is that the cluster is looks like a single > protection domain with nodes contributing resources.   A Larry says a ps > is cluster-wide.  TCF had the idea of features that each node provides > (ISA, floating-point unit, AP, /etc/..) so if a process needed specific > resources, it would only run on a node that had those resources.   But > it also meant that processes could be migrated from a node that had the > same resources. > > One of the coolest demos I ever saw was we took a new unconfigured PS/2 > at a trade show and connected the ethernet to it on the trade show > network, and put in a boot floppy. We dialed back into a system at an > LCC, and filled in some security things, details like the IP address of > the new system and soon it booted and joined the cluster.   It > immediately started to add services to the cluster, we walked away, and > (overnight) the system had set up the hard disk and started caching > locally things that were needed for speed.  Later I was editing a file > and from another screen migrated the process around the cluster while > the editing was active. > > The problem with VPROC (like VFS) is it takes surgery all over the > kernel.   In fact, for Linux 2.x kernel the OpenSSI >  folks did all the kernel > work to virtualize the concept of process, which sadly never got picked > up as the kernel.org folks did not like it (a real > shame IMO).   BTW, one of the neat side effects of a layer like VPROC is > things like checkpoint/restart are free -- you are just migrating a > process to the storage instead of an active processor. > > Anyway, Mosix has a lot of the same types of ideas.  I have much less > experience with it directly. > > > > _______________________________________________ > COFF mailing list > COFF at minnie.tuhs.org > https://minnie.tuhs.org/cgi-bin/mailman/listinfo/coff > -- voice: +1.512.784.7526 e-mail: sauer at technologists.com fax: +1.512.346.5240 Web: https://technologists.com/sauer/ Facebook/Google/Skype/Twitter: CharlesHSauer From dave at horsfall.org Wed Apr 7 07:20:50 2021 From: dave at horsfall.org (Dave Horsfall) Date: Wed, 7 Apr 2021 07:20:50 +1000 (EST) Subject: [COFF] Happy birthday, the Internet! Message-ID: Born on this day in 1969 with the publication of RFC-1 "Host Software" by Steve Crocker, it basically specified the ARPAnet and the IMPs. Oh, and it really peeves me when the stupid media call it "the internet"; it's a proper noun, hence is capitalised. -- Dave From gtaylor at tnetconsulting.net Wed Apr 7 08:01:46 2021 From: gtaylor at tnetconsulting.net (Grant Taylor) Date: Tue, 6 Apr 2021 16:01:46 -0600 Subject: [COFF] Happy birthday, the Internet! In-Reply-To: References: Message-ID: On 4/6/21 3:20 PM, Dave Horsfall wrote: > Oh, and it really peeves me when the stupid media call it "the > internet"; it's a proper noun, hence is capitalised. /The/ /Internet/ is one of a number of /internets/. With "the" and the capital I referencing a specific one. Sadly we are starting see the bifurcation of The Internet. -- Grant. . . . unix || die -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 4013 bytes Desc: S/MIME Cryptographic Signature URL: From jim at deitygraveyard.com Wed Apr 7 08:57:54 2021 From: jim at deitygraveyard.com (Jim Carpenter) Date: Tue, 6 Apr 2021 18:57:54 -0400 Subject: [COFF] Happy birthday, the Internet! In-Reply-To: References: Message-ID: On Tue, Apr 6, 2021 at 5:21 PM Dave Horsfall wrote: > > Born on this day in 1969 with the publication of RFC-1 "Host Software" by > Steve Crocker, it basically specified the ARPAnet and the IMPs. That website is wrong. Saying the Internet's birthday is when RFC-1 came out is like saying a child's birthday is when mom's water broke. It was getting close but it was not born yet. I'll celebrate October 29, which is when the first data went over the Arpanet. But even that isn't really correct, as the Internet is a network of networks and Arpanet was all alone. Jim From rudi.j.blom at gmail.com Wed Apr 7 13:38:47 2021 From: rudi.j.blom at gmail.com (Rudi Blom) Date: Wed, 7 Apr 2021 10:38:47 +0700 Subject: [COFF] Happy birthday, the Internet! Message-ID: did you know ... capitalising internet means you have to hold the shift-key -- the more I learn the better I understand I know nothing. From jnc at mercury.lcs.mit.edu Wed Apr 7 14:04:14 2021 From: jnc at mercury.lcs.mit.edu (Noel Chiappa) Date: Wed, 7 Apr 2021 00:04:14 -0400 (EDT) Subject: [COFF] Happy birthday, the Internet! Message-ID: <20210407040414.87C6D18C0A7@mercury.lcs.mit.edu> Re: [COFF] Happy birthday, the Internet! > From: Jim Carpenter > But even that isn't really correct, as the Internet is a network of > networks and Arpanet was all alone. Correct: the ARPANET was merely an ancestor (albeit an important one) of the Internet. (The most important, in terms of technical influence, was CYCLADES, "the key intermediate technical step between the ARPANET and the Internet".) The ARPANET was later sort of subsumed into the Internet, as its original long-haul backbone ("sort of" because the ARPANET's main protocol was discarded, in doing so), but that's not too important. If you want to select _a_ birthday for the Internet, I'd pick the day they settled on the IPv4 packet format; we know when that was, it was the second day of the 15/16 June, 1978 meeting (see IEN-68). I'm not wedded to that date, if someone has a better suugestion (e.g. the firt PRNET to ARPNET test), I'm open to hearing why the alternative's preferable. Noel From gtaylor at tnetconsulting.net Thu Apr 8 05:20:19 2021 From: gtaylor at tnetconsulting.net (Grant Taylor) Date: Wed, 7 Apr 2021 13:20:19 -0600 Subject: [COFF] Happy birthday, the Internet! In-Reply-To: References: Message-ID: On 4/6/21 9:38 PM, Rudi Blom wrote: > did you know ... > > capitalising internet means you have to hold the shift-key Nonsense. I can press the caps-lock key, type the "I", and then press the caps-lock key again. I'm sure there's a copy and paste method too. ;-) -- Grant. . . . unix || die -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 4013 bytes Desc: S/MIME Cryptographic Signature URL: From grog at lemis.com Thu Apr 8 10:01:45 2021 From: grog at lemis.com (Greg 'groggy' Lehey) Date: Thu, 8 Apr 2021 10:01:45 +1000 Subject: [COFF] Typing "Internet" (was: Happy birthday, the Internet!) In-Reply-To: References: Message-ID: <20210408000145.GB32218@eureka.lemis.com> On Wednesday, 7 April 2021 at 13:20:19 -0600, COFF wrote: > On 4/6/21 9:38 PM, Rudi Blom wrote: >> did you know ... >> >> capitalising internet means you have to hold the shift-key > > Nonsense. > > I can press the caps-lock key, type the "I", and then press the > caps-lock key again. ... assuming that you have a CapsLock key. > I'm sure there's a copy and paste method too. ;-) Or a spell checker. Or an Emacs macro :-) Greg -- Sent from my desktop computer. Finger grog at lemis.com for PGP public key. See complete headers for address and phone numbers. This message is digitally signed. If your Microsoft mail program reports problems, please read http://lemis.com/broken-MUA.php -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 163 bytes Desc: not available URL: From skogtun at gmail.com Thu Apr 8 19:06:37 2021 From: skogtun at gmail.com (Harald Arnesen) Date: Thu, 8 Apr 2021 11:06:37 +0200 Subject: [COFF] Typing "Internet" (was: Happy birthday, the Internet!) In-Reply-To: <20210408000145.GB32218@eureka.lemis.com> References: <20210408000145.GB32218@eureka.lemis.com> Message-ID: <1ef2630c-347d-fd11-f607-e6b6ec1d4a5e@gmail.com> Greg 'groggy' Lehey [08/04/2021 02.01]: > On Wednesday, 7 April 2021 at 13:20:19 -0600, COFF wrote: >> On 4/6/21 9:38 PM, Rudi Blom wrote: >>> did you know ... >>> >>> capitalising internet means you have to hold the shift-key >> >> Nonsense. >> >> I can press the caps-lock key, type the "I", and then press the >> caps-lock key again. > > ... assuming that you have a CapsLock key. > >> I'm sure there's a copy and paste method too. ;-) > > Or a spell checker. Or an Emacs macro :-) Or you can install something like "matchbox-keyboard" and use the mouse for everything :-) -- Hilsen Harald From tih at hamartun.priv.no Thu Apr 29 17:02:01 2021 From: tih at hamartun.priv.no (Tom Ivar Helbekkmo) Date: Thu, 29 Apr 2021 09:02:01 +0200 Subject: [COFF] DEC terminal line driver chips? Message-ID: I've got a number of DEC terminals, ranging from the VT220 to the VT520 (sadly, I got rid of my VT100 and VT102 many years ago, before I started collecting DEC equipment instead of just using it), and some of them have one or more burned out serial ports. Before I start taking them apart to find out what chips were used, I figured I'd check if any of you folks happen to know. I'd like to order a stash of replacements, and it would be nice to have them handy before I clear the work bench to start dismantling terminals... Oh, and for the record: the Q-bus PDP-11/23 uses 9636ACP and 9637ACP for output and input, respectively, while the VAX-11/630 substitutes a 9639ATC optocoupler for the 9637ACP differential receiver. (I have a couple of spare CPU boards with damaged ports, as well, so these are all on my shopping list already.) -tih -- Most people who graduate with CS degrees don't understand the significance of Lisp. Lisp is the most important idea in computer science. --Alan Kay From dave at horsfall.org Thu Apr 29 18:57:38 2021 From: dave at horsfall.org (Dave Horsfall) Date: Thu, 29 Apr 2021 18:57:38 +1000 (EST) Subject: [COFF] Dilbert on Unix Message-ID: https://dilbert.com/strip/1993-11-09/ Ageless... -- Dave From brad at anduin.eldar.org Thu Apr 29 22:21:49 2021 From: brad at anduin.eldar.org (Brad Spencer) Date: Thu, 29 Apr 2021 08:21:49 -0400 Subject: [COFF] DEC terminal line driver chips? In-Reply-To: (message from Tom Ivar Helbekkmo via COFF on Thu, 29 Apr 2021 09:02:01 +0200) Message-ID: Tom Ivar Helbekkmo via COFF writes: > I've got a number of DEC terminals, ranging from the VT220 to the VT520 > (sadly, I got rid of my VT100 and VT102 many years ago, before I started > collecting DEC equipment instead of just using it), and some of them > have one or more burned out serial ports. Before I start taking them > apart to find out what chips were used, I figured I'd check if any of > you folks happen to know. I'd like to order a stash of replacements, > and it would be nice to have them handy before I clear the work bench to > start dismantling terminals... > > Oh, and for the record: the Q-bus PDP-11/23 uses 9636ACP and 9637ACP for > output and input, respectively, while the VAX-11/630 substitutes a > 9639ATC optocoupler for the 9637ACP differential receiver. (I have a > couple of spare CPU boards with damaged ports, as well, so these are all > on my shopping list already.) > > -tih I will not speak specifically about DEC serial terminals, but rather an experience I had many years ago with Data General terminals at the University I was at that may or may not be helpful. I spent part of a summer fixing the DG terminals. The problems mostly in that case were the last set of driver chips after the CPU that blew. The University was running a current loop set up with very long runs all over campus and lightening would tend to take out a serial terminal from time to time. We later build our own lightening suppressors, but that is another story. Only in one case I remember did we blow a CPU. In the case of the DG, the CPU was an 8085 or some variant that had a serial port on it. This then was sent to a set of driver level chips that did the 5v TTL serial to whatever you needed conversion, be it regular RS-232 or the current loop specification that was used. The terminal took both and it was this last set of drivers that would often burnout. We usually found out what was really wrong by just replacing the drivers and if that didn't work, replace the CPU. We also saw many cases where a terminal would transmit but not receive, or vise versa. We tested for this too with a cross over cable from another known working terminal. You did not mention the age of these terminals, but I would also suspect caps going bad somewhere. In any case, good luck. If you have a cheap scope, available for just a small bit of $ on Amazon, you may be able to determine where the problem actually is in a much simpler way if you can't get the schematics. Serial ports are pretty slow and pretty simple to see with a scope. Of course, if you can find schematics it will be a whole lot simpler. -- Brad Spencer - brad at anduin.eldar.org - KC8VKS - http://anduin.eldar.org From clemc at ccc.com Thu Apr 29 23:17:27 2021 From: clemc at ccc.com (Clem Cole) Date: Thu, 29 Apr 2021 09:17:27 -0400 Subject: [COFF] DEC terminal line driver chips? In-Reply-To: References: Message-ID: If you look at the schematics for the VT-100 (which are available on bitsavers) as well as most terminals of the day used the Motorola MC1488/1489 driver pairs [early on, TI marked them as 75488/75498 but I doubt you'll see that old]. Anyway, for any terminal of those times, I'd be surprised if the later devices (like VTx20 series) did not them [the issue with these devices is you need all of 5 and +/- 12 volts]. These terminals are new enough that they might have used MAX232 (single 5 v power - there are even 3.3v versions these days). All of these devices are very available online. I would suggest putting high quality (*i.e.* auget style / machined pins) sockets. The nice thing about 1488/1489 is that they were doped to fuse the output section on failure, so just replacing them will in fact resurrect most serial port failures. Frankly, I never understood why more manufacturers did not put them in sockets for easy replacement. That said before you open up the case, I make sure you are cabled correctly. If you are using so-called 3-wire cables, then you need to ensure RTS/CTS [4-5] are strapped and DSR/DCD/DTR [6/8/20] are also strapped. The terminal will ignore any I/O unless it sees these pins asserted. On Thu, Apr 29, 2021 at 3:11 AM Tom Ivar Helbekkmo via COFF < coff at minnie.tuhs.org> wrote: > I've got a number of DEC terminals, ranging from the VT220 to the VT520 > (sadly, I got rid of my VT100 and VT102 many years ago, before I started > collecting DEC equipment instead of just using it), and some of them > have one or more burned out serial ports. Before I start taking them > apart to find out what chips were used, I figured I'd check if any of > you folks happen to know. I'd like to order a stash of replacements, > and it would be nice to have them handy before I clear the work bench to > start dismantling terminals... > > Oh, and for the record: the Q-bus PDP-11/23 uses 9636ACP and 9637ACP for > output and input, respectively, while the VAX-11/630 substitutes a > 9639ATC optocoupler for the 9637ACP differential receiver. (I have a > couple of spare CPU boards with damaged ports, as well, so these are all > on my shopping list already.) > > -tih > -- > Most people who graduate with CS degrees don't understand the significance > of Lisp. Lisp is the most important idea in computer science. --Alan Kay > _______________________________________________ > COFF mailing list > COFF at minnie.tuhs.org > https://minnie.tuhs.org/cgi-bin/mailman/listinfo/coff > -------------- next part -------------- An HTML attachment was scrubbed... URL: From ewayte at gmail.com Thu Apr 29 23:25:23 2021 From: ewayte at gmail.com (Eric Wayte) Date: Thu, 29 Apr 2021 09:25:23 -0400 Subject: [COFF] Dilbert on Unix In-Reply-To: References: Message-ID: And this one: https://dilbert.com/strip/1995-06-24/ On Thu, Apr 29, 2021 at 04:57 Dave Horsfall wrote: > https://dilbert.com/strip/1993-11-09/ > > Ageless... > > -- Dave > _______________________________________________ > COFF mailing list > COFF at minnie.tuhs.org > https://minnie.tuhs.org/cgi-bin/mailman/listinfo/coff > -- Eric Wayte -------------- next part -------------- An HTML attachment was scrubbed... URL: From dave at horsfall.org Fri Apr 30 17:34:59 2021 From: dave at horsfall.org (Dave Horsfall) Date: Fri, 30 Apr 2021 17:34:59 +1000 (EST) Subject: [COFF] DEC terminal line driver chips? In-Reply-To: References: Message-ID: On Thu, 29 Apr 2021, Brad Spencer wrote: > I will not speak specifically about DEC serial terminals, but rather an > experience I had many years ago with Data General terminals at the > University I was at that may or may not be helpful. [...] We had a network of serial lines extending for several km over a few suburbs; after every lightning strike I would get to replace the 1488/1489 chips which were *soldered* in. Eventually I just bought a set of high-quality sockets, and merely swapped the chips as each terminal came in after being zapped by Thor. As an aside, not only did I chuck out the bad chips but I took care to bend their pins over backwards, in case some idiot saw them... -- Dave, who once destroyed a $US10,000 Ethernet card for the CCI Power 6/32 From dave at horsfall.org Fri Apr 30 17:42:04 2021 From: dave at horsfall.org (Dave Horsfall) Date: Fri, 30 Apr 2021 17:42:04 +1000 (EST) Subject: [COFF] DEC terminal line driver chips? In-Reply-To: References: Message-ID: On Thu, 29 Apr 2021, Clem Cole wrote: > That said before you open up the case, I make sure you are cabled > correctly.   If you are using so-called 3-wire cables, then you need to > ensure RTS/CTS [4-5] are strapped and DSR/DCD/DTR [6/8/20] are also > strapped.   The terminal will ignore any I/O unless it sees these pins > asserted.  I used to do that so often for so many terminals that I could practically do it in my sleep... Having the correct crimping tool also helped :-) -- Dave, who has yet to see a full implementation of RS-232 i.e. the secondary channel etc From tih at hamartun.priv.no Fri Apr 30 21:55:57 2021 From: tih at hamartun.priv.no (Tom Ivar Helbekkmo) Date: Fri, 30 Apr 2021 13:55:57 +0200 Subject: [COFF] DEC terminal line driver chips? In-Reply-To: (Brad Spencer's message of "Thu, 29 Apr 2021 08:21:49 -0400") References: Message-ID: Brad Spencer writes: Thanks for your advice, Brad! > The University was running a current loop set up with very long runs > all over campus and lightening would tend to take out a serial > terminal from time to time. That would do it. In my case, it's carelessness with connections between different in-house power circuits. I live in an older house, with three phases in, and pairs of them used for the individual 240v circuits, of which I have two in my hobby room. Imbalances (caused by exterior faults) can cause ugly spikes when connecting or disconnecting; I've become very careful about making sure all computer equipment in the room is on the same circuit, with good ground connections. ...which reminds me: I once worked for a company whose offices stretched throughout the same floor in two adjacent city buildings. Never really gave that fact a second thought, until I grabbed a grounded metal RS232 connector with one hand, rested the other on the grounded metal chassis of the machine it was connected to, and pulled the connector. The other end of the cable was grounded in the other building. I needed a short break after that before continuing work... > You did not mention the age of these terminals, but I would also > suspect caps going bad somewhere. Mm. Old caps do that. I recently had one blow in a DEC BA23 power supply, which I pulled, and replaced with a spare one I had on hand. That lasted all of five minutes before the same capacitor blew in the replacement. Turns out they have noise suppression caps on the line input, and these go bad and explode. Doesn't affect anything else, though, so I just swapped in new ones, and the supplies work fine. -tih -- Most people who graduate with CS degrees don't understand the significance of Lisp. Lisp is the most important idea in computer science. --Alan Kay From tih at hamartun.priv.no Fri Apr 30 22:12:37 2021 From: tih at hamartun.priv.no (Tom Ivar Helbekkmo) Date: Fri, 30 Apr 2021 14:12:37 +0200 Subject: [COFF] DEC terminal line driver chips? In-Reply-To: (Clem Cole's message of "Thu, 29 Apr 2021 09:17:27 -0400") References: Message-ID: Clem Cole writes: > [...] Motorola MC1488/1489 driver pairs [...] Thanks! That's useful info. I'll add a small pile of each to my shopping list. > [...] they might have used MAX232 [...] Ah, yes, I remember those. Checking Mouser now, I see that there's an awful lot of variants of them, though. I think maybe I should open up my VT520 (the newest terminal I have), and check what it's using. It's down from four to one working serial interface, and it's such a nice terminal, I'd really like to have it fully operational. > If you are using so-called 3-wire cables, [...] I usually call those RS-237. :) -tih -- Most people who graduate with CS degrees don't understand the significance of Lisp. Lisp is the most important idea in computer science. --Alan Kay