test-drb September 2018

test-drb@ccmp.vtda.org

141 participants
154 discussions

by jnc＠mercury.lcs.mit.edu

> From: Mattis Lind > The H744 is a buck converter. You can read about buck converters here: > https://en.wikipedia.org/wiki/Buck_converter Wow, that was incredibly hard to read; no clear and simple explanation of the basic concept of how it works, before getting into the details! If I understand it correctly, it stores part of the incoming energy of a block of current in the field around the inductor; later, switches change state to create a loop that includes the inductor, and it uses the stored energy to cause electrons to flow around the new (temporary, because of the switch) circuit. Is that about right? The H744 manual doesn't really talk much about that aspect of the circuit's operation (at least in terms of 'we use this trick to get all the energy out of the incoming current flow'); it just describes the stuff around the coil as "an LC filter". It says "This type circuit is basically only an averaging device", which I wouldn't say is really on point - that would describe my (incorrect) prior description as well as the correct one. And just to make it even more confusing, it says "most of the input voltage is absorbed across the emitter-collector of Q5", but I looked, and Q5 is tiny, and I eventually figured out that that only applies to the +15V needed to run the voltage regulator. Noel

6 years, 3 months

Advice requested on proper disposal of Seagate ST3000DM001 disk drives

by spacewar＠gmail.com

Anyone have advice on making thermite? Ingredients, sources, proportions? The internet seems to think that just using aluminum powder with ferric oxide is relatively hard to ignite, and that some manganese dioxide would help with that. Without spending too much time shopping, it looks like I can get: * aluminum powder, 5 micron, 2 lb for $34 * ferric oxide, 10 lb for $27 * manganese dioxide, 1 lb for $39

6 years, 3 months

DEC H744 +5 supply

by jnc＠mercury.lcs.mit.edu

Oh, one thing I forgot to include: > a lot of the incoming power in that 30V AC has to be thrown away, in > producing +5V. So, if my understanding is correct, the 'switching' H744 really isn't much better than a classic linear supply. It still wastes a very large amount of the input power, and it still has a massively heavy transformer in it. Yes? So I wonder what exactly the advantage was in going to the switching approach? Yes, it keeps the output voltage steadier then a pure linear supply could - but I'll bet there are analog approaches that can do the same. (They'd need something that can produce a steady reference voltage, but the switching approach needs, and has, the same thing.) Maybe the main output transistors are happier being full-on or full-off, or something like that? Noel

6 years, 3 months

Advice requested on proper disposal of Seagate ST3000DM001 disk drives

by jnc＠mercury.lcs.mit.edu

> From: Eric Smith > That's way too good for these *&#$ing ST3000DM001 drives, and won't > provide anywhere near enough sense of satisfaction. https://www.youtube.com/watch?v=Gxm_qpKh7Jw 'Nuff said. Noel

6 years, 3 months

DEC H744 +5 supply

by jnc＠mercury.lcs.mit.edu

So there's something about the H744 I'm not sure I understand; hopefully those with more analog-fu will set me straight if I'm confused. This supply runs off 20-30V AC. It takes the input AC, rectifies it, and runs it through a cap to filter out the ripple. What's next is that it's an early switching supply; i.e. the electronics inside switches that newly-created main DC off and on very quickly to keep the output voltage at around +5V. However... My understanding is that, without using a transformer (which creates an independent circuit loop - more below), there's no way to increase the _amperage_ out of circuit over what's fed into it: since amps are electrons/second, the electrons/second out more or less have to equal electrons/second in, since one can't easily 'create' electrons - at least, in normal electonic gear! (Transformers, by creating a whole new circuit loop, can 'create' more electrons/second in the new loop; since they tie the 'out' of the new circuit back to its 'in', they can recirculate the 'extra' electrons.) And to the extent that the output is at lower voltage, the energy differential has to be dumped; hence the huge heat sinks - a lot of the incoming power in that 30V AC has to be thrown away, in producing +5V. Right? My (possibly confused) understanding is that later switching supplies take the incoming 60Hz wall AC, transform it to a higher frequency, run _that_ through a transformer (which can be a lot smaller, since it's at a higher frequency, and the higher the frequency, the smaller the transformer you can use - hence the use of high frequency AC in airplanes, to allow use of smaller - and thus lighter - transformers). That then turns out a massive amount of amps in the output loop (since with a transformer, energy out is roughly energy in, modulo resistive losses; and with constant power, if V goes down, I goes up). So the losses are a lot lower - N amps at 110V in produce ~20N amps out at +5V. (Well, depending on all the losses, ~20.) And the whole works is a lot lighter, to boot. Did this programmer get all that analog stuff correctly? Thanks! Noel

6 years, 3 months

GE2149G206 Bit slice CPU??

by holm＠freibergnet.de

Hi all, I've got an VME Bus sized CPU or GPU Board out of ebay a while before, it is equipped with 4 pcs of AM29203 Slices and an AM2910A Sequencer. It sems to be a german Product. The Sticker on one of the DIN 96 Connectors states: GE2149G206 WNr. 10488 Grund- Baugruppe Does anyone know what it is or where is it coming from? Kind Regards, Holm -- Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583 info at tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741

6 years, 3 months

HP 2000 /2100 emulator ?

by pete＠petelancashire.com

I will soon have a teletype model 35 all cleaned up and running Why like is some suggestions for something I can put in the base and emulate an HP 2000 or even in modern 2100 my goal is nothing serious I'd love to be able to do HP basic and find the version of Star Trek I think that was the name of the game just show I can demonstrate the friends how cool these machines were. If I could have my dream come true the emulator would be on a little SBC running Linux t Or even a simple OS that upon being powered up it would display login or was that log on on the teletype pretty much having the coat hard-coated but still having an area for saving files. Thanks and thanks for all the previous assistance members of this group of this list have given me

6 years, 3 months

Advice requested on proper disposal of Seagate ST3000DM001 disk drives

by cym224＠gmail.com

On 20 September 2018 at 23:20, Eric Smith via cctalk <cctalk at classiccmp.org> wrote: > Anyone have advice on making thermite? Ingredients, sources, proportions? > NIST SP 800-88 Rev. 1? There is some milspec about sanding the platters that actually specified what grit to use but I do not remember the title. N.

6 years, 3 months

Floating point math in FORTRAN IV on PDP-8

by engwalljonathanthereal＠gmail.com

My SIMH resists anything but Adventure, I am working through a Fortran IV. I think you break from the loop and confuse the machine using i. That with some error checking: .TYPE FLOAT.FT ????? DO 50 X=1,100 ????? F = FLOAT(X) ????? G = SQRT(F) IF (G) (11,11,90) 11 WRITE(4,75) G 75 FORMAT(H 5,ERROR) 90?? H = ALOG(F) ????? WRITE(4,99) F,G,H 99?? FORMAT(' ',E12.6,E12.6,E12.6) 50??? CONTINUE WRITE(4,100) F,G,H 100?? FORMAT(' ',E12.6,E12.6,E12.6) ????? END My for fortran IV book and I are the same age,LoL Jonathan Engwall engwalljonathanthereal at gmail.com On September 19, 2018, at 11:10 PM, mark--- via cctalk <cctalk at classiccmp.org> wrote: Hi Kyle Just out of interest I ran this on VAX Fortran (Compaq Fortran 77 6.6-201) and I think got the results expected: $ type for004.dat 1.000000 1.000000 0.000000 2.000000 1.414214 0.693147 3.000000 1.732051 1.098612 4.000000 2.000000 1.386294 5.000000 2.236068 1.609438 ... 98.000000 9.899495 4.584968 99.000000 9.949874 4.595120 100.000000 10.000000 4.605170 However, I am no Fortran expert! Regards, Mark. -----Original Message----- From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Kyle Owen via cctalk Sent: Wednesday, September 19, 2018 11:44 PM To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> Subject: Floating point math in FORTRAN IV on PDP-8 At VCF MW this past weekend, I was playing around with an FPP8/A stuffed into a PDP-8/M with a fan removed. This hex-wide two-board set will happily work in a quad-wide backplane, as it needs no signals that an 8/A would otherwise provide. I wanted to benchmark the FPP8/A with the software emulation that FORTRAN IV supposedly does. Mind you, I also don't have an EAE in mine, so software emulation for integer multiplication/division would also be used. I tried running a simple program to print some natural logs and square roots, which ran quite well with the FPP8/A in place. Without the FPP8/A...all of the results were wrong. Significantly. Negative numbers in many cases. No clear pattern as to what it's doing. Would anyone be able to try my program on some other real hardware (or another emulator) to verify? With and without EAE would also be desirable. I'm not sure how to disable the EAE in SIMH, else I'd try that too. Here's what SIMH looks like with my program: PDP-8 simulator V4.0-0 Current git commit id: d35b8725 sim> at rk0 disk2.fortran.rk05 sim> b rk .TYPE FLOAT.FT DO 50 I=1,100 F = FLOAT(I) G = SQRT(F) H = ALOG(F) WRITE(4,100) F,G,H 50 CONTINUE 100 FORMAT(' ',F12.6,F12.6,F12.6) END .R F4 *FLOAT/G$ 1.000002 1.000002 0.000000 2.000002 1.414215 0.693147 3.000002 1.732053 1.098614 4.000002 2.000002 1.386296 5.000002 2.236070 1.609439 [snip] 98.000001 9.899495 4.584968 99.000000 9.949874 4.595121 100.000023 10.000008 4.605171 . Much appreciated, Kyle

6 years, 3 months

In search of microchannel P390 card...

by ian.finder＠gmail.com

If you have a lead on one, please ping me off-list. I have a very specific project I'm trying to accomplish. thanks

6 years, 3 months

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test-drb September 2018