test-drb January 2015

test-drb@ccmp.vtda.org

175 participants
253 discussions

by evan＠snarc.net

Cctalk'rs, Very exciting news to share tonight. Al Katz and Sol Libes, who co-founded the Trenton Computer Festival based on Roger Amidon's idea, gave we "MARCHins" permission to publish their video of ENIAC's John Mauchly keynoting the 1977 show. It was the first TCF keynote: there wasn't one at the 1976 show. Claude Kagan (a Western Electric engineer who also ran a 1960s/1970s high school computer club here in central New Jersey) gave the introduction. There are also remarks by Kay Mauchly, who was an ENIAC programmer, followed by some audience Q&A. A few minutes of the video are choppy due to the original source. Please share this far and wide! Video is in two parts so here's the playlist: https://www.youtube.com/playlist?list=PL_e5fSxflvrxXO5Ddh9ZXX-cli94zF3Pc

10 years, 3 months

NTP on classiccmp

by jwest＠classiccmp.org

I just noticed that NTP on classiccmp stopped, it has been restarted. My apologies, but you?ll probably want to scroll back ? day to catch any unread messages if you didn?t notice it! J

10 years, 3 months

Free hosting for all classiccmp sites

by jwest＠classiccmp.org

Sean wrote.... ------------ I have Comcast business grade cable Internet to my home and I'm already hosting my own personal site and sites for a few other folks; no data caps; plenty of static IPs; not terribly slow; everything's protected with a Liebert double-conversion UPS... not totally a commercial datacenter in terms of available bandwidth or backup power capacity but nevertheless my uptimes are decent. ------------ I have said many times in the past, but as new list members pop on they are probably not aware of this. I host the classiccmp server (which is not just the classiccmp mailing list, but a growing truckload of user websites that are classiccmp related) gratis. I do not host it on a "Comcast business grade cable internet" connection (there's a contradiction in terms in and of itself...) This is not something I "run out of my home". One of the companies that I own is a hosting provider. We have a rather large-ish datacenter and I have dedicated a set of resources to classiccmp. Our bandwidth is many orders of magnitude greater than a "home or business connection". Not to mention, it's managed bandwidth with load balanced connections to multiple carriers. Our infrastructure is all xenserver based, so spinning up new VM's is a mouseclick. We have quite a few SAN's so storage is not a problem at all. Full HVAC monitoring & control, power backups (oh, and we have two separate powerstations from Ameren UE ON SITE). This infrastructure is professionally managed by my company 24x7. Long story short... it's not a "home" connection. More to the point, since I own the company, rest assured that hosting your site here is not a "till the boss finds out" or "my wife accidentally turned off the computer" type of situation. As a result - I'm happy to host any website, ftp site, wiki, etc. etc. that is classic computer related. As long as it meets that criteria, you can host your site with us for no charge. Best, J

10 years, 3 months

front panel LED help sought

by jnc＠mercury.lcs.mit.edu

> From: Robert Jarratt >> I've replaced LEDs many times without thinking what I am fitting. > "without thinking" is that an impostor pretending to be Tony? :-) :-) Foolish novice! Please consult: http://en.wikipedia.org/wiki/Hacker_koan#Enlightenment for enlightenment. :-) Noel

10 years, 3 months

Answer: Weekly Classic Computer Trivia Question (20150112)

by dpi＠dustyoldcomputers.com

More discussion ensued than was expected for this question. On a minimal 4k machine (no extended memory and no EAE) and no data break devices operating the longest latency would be that of a memory reference instruction with a defer (indirect address) cycle. On a Straight 8 this would be 4.5 microseconds. A single cycle data break device could have delayed the interrupt indefinitely although I know of no such devices. A three cycle break could extend the delay by an additional three memory cycles (4.5 microseconds) for a total of 9 microseconds. If the machine was equipped with an EAE then the Division instruction would have delayed entry of the interrupt service routine by up to 35 microseconds (on a straight 8). I believe this was a 9 microsecond instruction on the 8/e EAE. If the machine is equipped with extended memory then there is the CIF induced delay. CIF is the Change Instruction Field instruction. This instruction only schedules the change. The actual change does not take place until the next JMP I or JMS I instruction. The interrupts are masked by the CIF until the conclusion of the indirect branch. This is because the interrupt handler would not be able to restore the instruction field correctly in this instance. I have been unable to think of a reason why you would ever want to delay the indirect branch although you certainly could do so. That means the sequence CIF followed by a JMS I would only see the additional delay from the JMS I which is the same as the delay from a memory reference instruction with a defer. The JMP I variant would only be 3 microseconds. And the greatest source of interrupt latency on a straight 8 would have been due to the Option 189 which is the low cost A/D converter. This option added the ability to do 6 to 12 bit A/D conversions as a CPU instruction (6004). It performed a typical successive approximation conversion using the MB and AC registers. When 12 bit conversion were selected this instruction would take 56.6 microseconds to execute according to the manual. I don't have a 189 for my straight 8 but I am planning on hunting down the cards I don't have. And the answer Mr Stearns gave for this question was "No matter what it is faster than Windows." On Mon, Jan 12, 2015 at 9:10 AM, Doug Ingraham <dpi at dustyoldcomputers.com> wrote: > This weeks question comes from Warren Stearns. It is a little obscure and > specific to the PDP-8 family of computers. > > What is the source of the greatest latency in the interrupt system on a > PDP-8. > > I have three answers, two of the answers depends on the options fitted to > an 8. > > Why would this have been an important question? Interrupt latency would > be extremely important in the field of data collection which was one of the > principal early uses of these machines. My particular 8 was used for > exactly this purpose in the Summer when it was hauled to a radar site and > collected weather research data for the Institute of Atmospheric Sciences. > I believe it was used for this from 1969 through 1972. I have several > hundred DECTapes with some of this data. The surprising thing is we don't > see any problems reading DECTapes that haven't been out of their box since > the early 70's. > > Doug Ingraham > PDP-8 S/N 1175 >

10 years, 3 months

Dan Tumey

by wh.sudbrink＠verizon.net

Is he on this list? The University of Iowa's PDP-8 restoration site says he is producing beautiful replacement Teletype hammer pads: http://homepage.cs.uiowa.edu/~jones/pdp8/UI-8/log.shtml I'd love to get a few for my tty. Bill S.

10 years, 3 months

Knowledge Base (was RE: Restoration technique [Was: Re: Bay Area: IBM 4341 and HP3000]

by jwest＠classiccmp.org

So.. about this "knowledgebase" of restoration techniques. Apparently new folks don't know and some older listmembers don't remember... We did start a "wiki" for people to post restoration tips, repair tips, etc. This was done about 8 years ago. When I first brought up the idea there was a lot of discussion on the list as to if it was a good idea or not. Many people had very good thoughts as to why it would be wonderful, and many other people had equally good thoughts as to why it would not be wonderful. In any case, I set it up. We found that there was an initial flurry of posting, and then virtually nothing. Statistics showed it was not used very much at all. There were a handful of issues as I recall (not my implementation of it, but in the general idea of a repair/troubleshooting/restoration "wiki"). I only remember one of them at the moment... and that was that someone would post an article without really having detailed expertise in that given area and then someone that DID have expertise in that area would (for lack of a better term) contramand that article or write a separate one with conflicting info which made it hard for a novice to really sift through the information. In short, everyone has an opinion and at times the articles directly conflicted with another and someone seeking knowledge wouldn't know who to believe. That being said, if people really want to give this another try, I would be happy to turn on the old classiccmp knowledge base (I'm 99% sure it's stored but just not turned on), or I could easily have one of my support staff dump a wiki installation to a folder there (under classiccmp) and we could give it a try again. I'm all for it, but for it to be successful - it has to be due to contribution/acceptance by the membership at large. My proclivity at this point would be to install a new wiki and then pull articles already posted in the old "wiki" into it. And yes, if it's to be in the classiccmp.org domain, I'd have to host it. I have not yet seen a scenario where we'd be willing to point an a-record off-site (but that's not to say some future situation might get a different response). Best, J

10 years, 3 months

Restoration technique [Was: Re: Bay Area: IBM 4341 and HP3000]

by jnc＠mercury.lcs.mit.edu

> From: Robert Jarratt > It wouldn't be hard to create a wiki where this kind of information is > collected > ... > Isn't there someone on the list who has been offering lots of server > capacity? It could be hosted there. Umm, that might have been me - I have offered to host things on a number of occasions, and do in fact host the older ClassicComputers archives (the newer ones are^H^H^Hwere at www.classiccmp.org). I'm not sure I can help in this case, though. I do have access to a lot of space (so hosting the archives is not a big deal), _but_ i) I'm a guest on this machine, and hosting active content like a wiki would be something I'd have to get OK'd, and ii) technically, hosting a wiki is a whole different ball of wax from hosting static content (which I can just put in place, and forget), and I'm not sure I have the time/energy. If someone did, that would be great, because I think a wiki about restoring old computers would be a really powerful resource. Not for detailed technical content (as someone already pointed out, we have the manuals), but for: - Articles laying out how to start, where to get stuff, what you need to know (with lists of recommended books/etc in fields such as digital logic, etc, etc) - Articles on what tools/etc it's useful to to have, and recommendations for manufacturers, models etc (e.g. an oscilloscope is pretty much a must), and where to find them cheap - Lists of which systems are good targets (because they're easy to find, have good documentation available, parts availability is good, etc, etc) - Articles on specific topics which aren't covered in literature (e.g. the whole discussion about capacitor reforming; the heat soak for old tapes/floppies, etc) - Etc, etc, etc. All stuff that's not really written down anywhere, but which a beginning collector (especially one who didn't work on these things 'back in the day') would find invaluable. Noel

10 years, 3 months

Announcing TCP/IP for RSX-11M-PLUS

by jnc＠mercury.lcs.mit.edu

> From: Johnny Billquist > And tcp/ip already exists. At least on TOPS-20. There are at least two TCP/IP's for PDP-10's - the other, written by Ken Harrenstien, is the one for ITS. I'm not sure how closely related the TWENEX one is the TENEX one done at BBN - I vaguely seem to recall that DEC re-wrote it extensively, but I don't know much about that code. > From: Pontus Pihlgren > Do you mean to say that bytes are 8-bit wide on PDP-11? Why would > PDP-10 be so much harder?3 TCP/IP header fields are all multiples of 8 bits. So anytime you want to read/write one on a PDP-10, you have to start LDB'ing and DPB'ing through byte pointers/descriptors all over the place. Which I'm sure is no biggie for most experienced PDP-10 coders, but it would drive me bonkers. Noel

10 years, 3 months

Compaq Portable knob

by dgriffi＠cs.csubak.edu

Does anyone here have a contrast knob from a Compaq Portable or good-looking substitute? -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

10 years, 3 months

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test-drb January 2015