test-drb

test-drb@ccmp.vtda.org

101090 discussions

by athornton＠gmail.com

From: Liam Proven <lproven at gmail.com> > To: "Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> > Subject: Re: Motor generator > > I think because for lesser minds, such as mine, [APL is] line noise. > > A friend of mine, a Perl guru, studied A-Plus for a while. (Morgan > Stanley's in-house APL dialect.) He said to me that "when I came back > to Perl, I found it irritatingly verbose..." and then was immediately > deeply shocked at the thought. > > I seriously think this is why Lisp didn't go mainstream. For a certain > type of human mind, it's wonderful and clear and expressive, but for > most of us, it's just a step too far. > > Ditto Forth, ditto Postscript, etc. > > Plain old algebraic infix notation has thrived for half a millennium > because it's easily assimilated and comprehended, and many arguably > better notations just are not. > > The importance of being easy, as opposed to being clear, or > unambiguous, or expressive, etc., is widely underestimated. > > Yes, that. C is a great assembly language preprocessor for a PDP-11. The PDP-11 is a beautiful, intelligible architecture, where things happen one at a time in sequence. This is easy to think about. Unfortunately it's got very little to do with the way that modern high-performance silicon gets stuff done. (Aside: it's also weird that the one-thing-at-a-time sequencing is the thing that feels logical and intuitive to us since it is absolutely not how our brains work.) I would argue that Forth and Postscript are hard to understand for a different reason than APL: APL is inherently vectorized, and requires, more or less, that you treat matrices as single entities. Not many people's brains work that way. It's hard enough to learn to treat complex numbers as single entities. Forth and Postscript require you to keep a really deep stack in your brain to understand the code, and people aren't really very good at doing that for more than three or four items (much fewer than 7 +/- 2). Both of these are much more difficult for most people to work with and reason about than something imperative and infix-based. The fundamental problem is the impedance mismatch between the way most people think (which would at the very least take a radical reframing of curricula to change, and might not work anyway: look at the failure of the New Math, which was indeed very elegant, taught mathematics from first principles as set theory, and was not at all geared to the way young children _actually learn things_) and where we can continue to squeeze performance out of silicon. This is really not tractable. I think our best hope is to make the silicon really good at generating and figuring out graphs so it can dispatch lots of pieces of what feels like a sequential problem in parallel and come out with the same answer as you would have gotten doing it the naive one-step-at-a-time way. But we've already done that, and, yeah, it mostly works, but the abstraction is leaky and then you get Meltdown and Spectre. I don't have any answers other than "move to Montana, drop off the grid, and raise dental floss." Adam

4 years, 6 months

Motor generator

by cctalk＠emailtoilet.com

Many thanks for all the info. I just wanted to make sure my recesses were right. I asked about MG because, in an audio forum, I see folks paying crazy money for AC cords and power line conditioners. I thought a good MG would solve many of the 'problems' they are trying to fix.

4 years, 6 months

Motor generator

by cctalk＠emailtoilet.com

In the deep recesses of my mind I seem to remember something about S/360 machines using a motor generator. If I am right was this to create a stable power source at a certain frequency or voltage?

4 years, 6 months

Lecture: Forth: from the minicomputer to the microcontroller, 2021-05-08, 19:00

by stueberahoo＠yahoo.de

Hi all, you're invited to the Update computer club[0] public lecture series "Updateringar"[1]! Update is a Swedish computer club founded in 1983 whose members tinker with all kinds of computers, from Raspberry Pi to PDP-12. The club has a big collection of historic computers. In this lecture series we'll talk about everything related to computers: Historic and modern computers, operating systems, programming, hardware projects, creating art with computers, building a computer museum, and more. When: 2021-05-08, 19:00 CEST Where: https://bbb.cryptoparty.se/b/upd-0mo-m2u-aq8 Forth: from the minicomputer to the microcontroller Forth is an almost esoteric programming language in the eyes of most modern programmers, but still worth learning if only to expand your horizon. On modern microcontrollers the strengths that made Forth stand out in on 1970s minicomputers are relevant once again: fast enough execution, low worst case latency, full control over the system, powerful metaprogramming, and interactive development. This presentation will show how to overcome the initially near vertical learning curve and get the Mecrisp Stellaris Forth system running on a STM32 microcontroller without breaking the bank. Prior exposure to microcontrollers or assembler is helpful, but not required. Once the Forth system is running we will use it to explore either the hardware it's running on or its implementation and available implementation tradeoffs. Jan Bramkamp (CCCHB) The lecture is free and open to everyone. Upcoming: 2021-06-12, 19:00: How to start and run a computer museum. Thiemo Eddiks (Oldenburger Computer-Museum) Hope to see you there, Anke P.S.: I hope this is not too offtopic, but I assume there are people interested in Forth here. [0] http://www.update.uu.se/index_eng.html [1] https://www.update.uu.se/wiki/doku.php/projekt:updateringar

4 years, 6 months

cctech Digest, Vol 80, Issue 5

by athornton＠gmail.com

Message: 18 > Date: Thu, 6 May 2021 15:18:04 +0200 > From: Liam Proven <lproven at gmail.com> > To: Jay Jaeger <cube1 at charter.net>, "General Discussion: On-Topic and > Off-Topic Posts" <cctalk at classiccmp.org> > Subject: Re: That VAXStation4000vlc 3W3 video connector > Message-ID: > < > CAMTenCGKYnC++cT2gfpCvvntTjv-FrvivhuoXLcjWDesf2WC9w at mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > On Wed, 5 May 2021 at 17:59, Jay Jaeger via cctalk > <cctalk at classiccmp.org> wrote: > > > I, for one, did find this helpful - one could make one of these up to > > test before possibly forking over the funds to build one properly. > > If anyone were up to making a small batch of these, I'd be happy to > pay for a few, plus shipping etc. I have 3 ? 4000VLCs and only 1 > monitor for 'em, and I hope to get them running again sometime... > > > I'd buy at least one, seeing as how it was my original question, and whatever I end up stitching together will be really gross. If whoever is doing it would ALSO do the much simpler DEC 15-pin to VGA adapter, I'd probably buy some of those too. Adam

4 years, 6 months

That VAXStation4000vlc 3W3 video connector

by prd＠decarchive.org

> On 4 May 2021, at 19:00, cctalk-request at classiccmp.org wrote: > > Message: 17 > Date: Mon, 3 May 2021 16:22:45 -0700 > From: Adam Thornton <athornton at gmail.com> > To: "General Discussion: On-Topic Posts" <cctech at classiccmp.org> > Subject: That VAXStation4000vlc 3W3 video connector > Message-ID: > <CAP2nic2zsyqsLo1dFTTPh4WFV6utS1Tt_4RMsROjsmw78+8zKQ at mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > I assume it would be way too much to hope that HD BNC would fit it? Does > anyone have a pointer to the actual physical dimensions of the itty-bitty > BNC-ish connector in the video port of the VAXStation4000vlc? If I can get > red, green, and blue out (assuming since there are only 3 connectors it's > sync-on-green) I can put together a sync splitter and turn it into VGA. I > have at least one decent multisync VGA monitor still, although none with > the RGB BNC inputs. Firstly, apologies if my response doesn't show up nicely in this thread --- I only receive the daily digests so I'm not sure how best to reply to a specific post... But on the subject of sourcing / making video cables with 3W3 connectors on one end, I also balked at the cost of the coaxial insets and decided to make an only marginally dodgy (if I do say so myself) cable out of half of an old VGA cable, three of the 'sleeves' / female connectors contained, in abundance, in every female D-sub connector, and a few bits of heat-shrink (see https://media.decarchive.org/DEC/VAX/VAXstation%204000-VLC/IMG_3941.jpg for a photo of this cable from an albeit sub-optimal angle). The resulting connections were surprisingly stable, however, were I to make another one, I'd replace the grounding alligator clip with a lug that can be screwed onto one of retaining nuts next to the VLC's 3W3 connector, and use longer bits of heat-shrink to fully insulate the outside of the RGB connectors... And just FYI, even as shown, the video quality was more than adequate (considering the resolution of the VLC's LCG framebuffer), however, I suppose one could always attach a shielded DA15 shell to provide a bit of extra noise suppression (as well as mechanical protection). Hope this helps, Peter

4 years, 6 months

PDP-8/I Negative-bus termination

by michael.99.thompson＠gmail.com

> > Date: Wed, 5 May 2021 00:03:05 -0700 > From: Josh Dersch <derschjo at gmail.com> > Subject: PDP-8/I Negative-bus termination > > Hey all -- > > Until this point I've never had any peripherals for my negibus systems > (apart from teletypes), and it occurs to me that I have no idea if the bus > needs to be terminated (and if so, with what). There are 6 slots in the > RF08 backplane (D01-D06) for daisy-chaining to the next device, which is > where I assume they'd go; the RF08 manual does not make it clear what this > looks like or if it's actually required, and I've gone through the > available PDP-8/I docs and I'm still at a loss. > > Can anyone with negibus experience point me in the right direction? > > Thanks, > Josh > The DEC Field Service Technical Manual has some notes on bus termination. It says: Termination is required on I/O cables longer than 20 ft., and may be desirable on shorter cables. For negative bus, use 220 Ohm shunt resistors to ground on IOP 1, IOP 2, IOP 4, BTS 1, BTS 3 and Initialize. No special termination module exists for the negative bus. -- Michael Thompson

4 years, 6 months

Motor generator

by michael.99.thompson＠gmail.com

> > Date: Wed, 5 May 2021 13:20:59 +0100 > From: <dave.g4ugm at gmail.com> > Subject: RE: Motor generator > > We had a Motor/Generator for our Honeywell L66. Not sure it was because it > wanted US voltages or just for a clean supply > Dave > I also worked on a Honeywell L66 that had two motor-generators. We used one at a time, and swapped the operational one each month. They cleaned up the noise in the incoming 208VAC 3-phase power, and the really heavy flywheel provided a little ride through for short term power drop outs. -- Michael Thompson

4 years, 6 months

400 Hz

by erik＠baigar.de

..not to forget, that the 400Hz equipment was readily available from powering aircraft on the ground before the engines take over. So although not cheap, they where cheaper than a custom design at an arbitrary new frequency

4 years, 6 months

400 Hz

by erik＠baigar.de

> Incidentally, a way to get three phase power at a frequency of your > choice is to use a "variable frequency drive". Please be careful with this! Have quite some experience in building three phase inverters from such small boxes for my various avionics projects. (1) The normal ones rectify the mains voltage (in EU this gives around 320V DC) and from this make PWM outputs on three lines. Yes, you can enter voltage and frequency (sometimes even more than 400Hz) digitally, but the outputs are ALWAYS PWM switching between 0V and 320V in the EU. Consequence: If you rectify these outputs you will get back your 320V, completely independent of your settings! You need to use a device called Sinus-Filter, i.e. a low pass using caps and Ls to smooth out and get rid of the PWM - only than you get the correct three phase. (2) The small boxes are only for motors (inductive loads). Connecting someting else (does not matter whether three phase or not) which e.g. has got EMC filters at the input containing caps, the relatively high frequency (e.g. 16kHz, often selectable) will easily toast them leading to a short. (3) The PWM-boxes do not isolate from mains, so you will have pretty high voltages at the PWM outputs with high frequencies which can be a challenge for isolations - so even if you set the inveter to 110V only, but power it >from 240Vmains, the isolation of your device needs to handle the full 320V! My biggest inverter based on such a small PWM motor drive inverter is described in my blog (including schematics)... http://www.baigar.de/TornadoComputerUnit/TimeLine.html#inverter1500 (4) DO NOT use these three phase boxes connecting one output and one input pin to your device thinking that this is a single phase output. Creating a "neutral" line at the output of such an inverter can be done, but it requires additional components and than you can use it as single phase device: Here I used a special transfomer after the Sinus filter with input in triangle and output in star configurations. So I get neutral PLUS insulation to mains... Good luck!

4 years, 6 months

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