test-drb May 2021

test-drb@ccmp.vtda.org

128 participants
102 discussions

by knowak＠alumni.calpoly.edu

Hi All, I have two Maxtor XT-4380E drives, one is a Series Code 3 and the other is 4. Is it OK to swap the boards between the two or is this a bad idea? They physically appear to look the same. Also a general question about PCB cleanup. Is there a method or solvent of some sort to clean boards? I've always used 99% alcohol in the past. -Kurt

4 years

Pipelining and Dec Jupiter thoughts....

by dick.curtis＠ymail.com

> From: Paul Koning <paulkoning at comcast.net> > Message-ID: <9D8BADA7-B597-42E1-99C8-4CC751F838C5 at comcast.net> > Another part of the puzzle was figuring out how to feed 100 watts of power to a chip,?> and get rid of that amount of heat, neither of which were anywhere close to what was > done at the time.? I still have some of the tech reports that describe that piece (and I?>contributed a wild idea -- which unfortunately DEC didn't get around to patenting?>before the project was shut down). Back in the mid-90s, there was an outfit in Britain which made some laptops using Alpha processors.? There was a rumor inside DECin the same time-frame about DEC engineers prototyping an Alpha-based laptop (which never made it to market). The rumor included the internal code-name... "BURNS". Dick

4 years

Pipelining and Dec Jupiter thoughts....

by dick.curtis＠ymail.com

On Friday, May 7, 2021, 11:07 CDT,?Zane Healy <healyzh at avanthar.com> wrote: > These if I needed OpenVMS on a laptop, I'd simply run it via emulator or virtualization?> (not an option for Itanium).? I gather that at least some development on OpenVMS 9.2 > is being done on VM's running on the developers laptops. Well, the latest version shipping from Bolton is V9.0-H, which has the long-awaited support for VMware, and IIRC some non-zero number of compilers available.? It's still pretty well set in the "bleeding-edge" field of software though.? It's labelled as V90EAK, with the last three letters indicating "Early Adopters' Kit", and made available to a rather small number of VMS customers who are interested in making their own products run on X64-86 platforms (as well as work properly on Itanics running v9.x) I don't know whether VSI has any particular policy about making the field test kits available to hobbyists/end-users quite yet.? Bear in mind that there's a LOT of VMS components which aren't really ready to use yet.? If memory serves, the V9.1 kit will also be labelled as 'field test', but will be made available to a larger number of customers/test sites, and is expected to include working versions of the components currently 'in progress'. Regards,Dick

4 years

400 Hz

by charlesmorris800＠centurytel.net

On 5/8/21 12:00 PM, cctalk-request at classiccmp.org wrote: > Message: 8 Date: Fri, 7 May 2021 21:59:08 +0000 From: W2HX > <w2hx at w2hx.com> To: Andrew Back <andrew at carrierdetect.com>, "General > Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> > Subject: RE: 400 Hz Message-ID: > <de37431b96cf4c82ba5ddb2b9daf1873 at EXBE015SV3.NA02.MSEXCHANGEOUTLOOK.COM> > Content-Type: text/plain; charset="utf-8" I will add that aircraft are > one of the main users of 400 Hz. This is because weight is always an > critical design consideration. So with smaller transformers, smaller > capacitors, etc, you can save a LOT of weight on electronic devices in > an aircraft. 73 Eugene W2HX -----Original Message----- From: cctalk > <cctalk-bounces at classiccmp.org> On Behalf Of Andrew Back via cctalk > Sent: Wednesday, May 5, 2021 11:26 AM To: cctalk at classiccmp.org > Subject: Re: 400 Hz On 05/05/2021 16:07, Grant Taylor via cctalk wrote: >> Were the higher frequencies used because it directly effected the >> amount of time / duration in (fractions of) seconds between peaks of >> rectified (but not yet smoothed) power? > Haven't read the rest of the thread and so at the risk of being profoundly wrong... Benefit of 400Hz mains is that transformers can be much smaller. Think of switching power supplies that rectify to DC and then switch up into kHz, which are then able to use far smaller transformer cores than an old linear PSU. At least this is a key motivation with 115V/400Hz 3-phase aviation power AFAIK. > > By coincidence we've just built a big 28VDC power supply, so that we can run a vintage 400Hz aircraft rotary inverter, which will then be used to power up old mil surplus kit that wants this. A classic adventure in yak shaving. Anyway, here's the 28VDC bit. > > https://www.rs-online.com/designspark/constructing-a-high-current-28v-dc-po… That's a very neat repackaging of the Lambda power supplies! Do they have the surge capability to start that rotary inverter (which may require a LOT more than 44 amps until the armature gets moving)... I hope you tested them first ;) I bought a 1 KVA 115V 400 Hz supply, a PP-7482/G from Fair Radio back when they still had them ("Reparable") a few years ago. The H-bridge TO-3 transistors were all blown, some with holes melted through their lids. I replaced them with BUX48A parts and it works again. It really sings that A-flat though ;) But I don't have anything to run with it! When I was young, 400 Hz surplus gear was a dime a dozen because no one had 400 Hz power. Now I do and all that gear has disappeared... -Charles WB3JOK/0 since '76 :)

4 years

400 Hz

by cctalk＠gtaylor.tnetconsulting.net

I have found the Motor Generator thread to be fascinating and enlightening. But it has made many a reference to the 400 Hz or other frequency much higher than mains line frequency. Despite the comments about the frequency, I'm still confused as to why the higher than mains frequency was used. Were the higher frequencies used because it directly effected the amount of time / duration in (fractions of) seconds between peaks of rectified (but not yet smoothed) power? I ask because it seems to me like the percentage of time / duty cycle of raw rectified but not yet smoothed) power would be the same at any and all frequencies. Is this assumption / understanding correct or completely off the mark? A few different people made references to the amount of capacitance needed at 400 Hz et al. vs 50/60 Hz mains frequency. Someone even spoke about high power DC being produced by polyphase converters and the possibility to tweak tweak winding voltages in order to possibly do away with the need for capacitors. Am I starting to understand the motivation behind the 400 Hz or is there something else behind it? Is this really playing to the (dis)charge time of capacitors in between peaks of rectified (but not smoothed) sources? Aside: I started a new thread for this very specific minutia to not mire the other Motor Generator thread down. Thank you for all the comments and those who respond to help me learn something new today. :-) -- Grant. . . . unix || die

4 years

400 Hz

by cctalk＠gtaylor.tnetconsulting.net

First, thank you to everyone who replied and gave me things to think about and learn from. On 5/5/21 9:26 AM, wrcooke at wrcooke.net wrote: > Hope this helps. Yes, indeed, very much. Thankfully, your description happened to mesh with the weird way that my brain processes things and your message just clicked confirming what I was learning but still processing what other people had written. Thank you Will. -- Grant. . . . unix || die

4 years

cctalk Digest, Vol 80, Issue 5

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

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

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

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

← Newer
1
...
5
6
7
8
9
10
11
Older →

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

test-drb May 2021