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.
> 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".
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'.
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.
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...
WB3JOK/0 since '76 :)
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
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
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."
Many thanks for all the info. I just wanted to make sure my recesses were
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.
you're invited to the Update computer club public lecture series
"Updateringar"! 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
When: 2021-05-08, 19:00 CEST
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
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,
P.S.: I hope this is not too offtopic, but I assume there are people
interested in Forth here.