test-drb

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101090 discussions

by alexandre.tabajara＠gmail.com

Dear sirs, Imagedisk is my savior, and I image all kind of disks I know with it :) But now I got a pair of TRS-80 model III single-sided disks. How do I image it using imagedisk? Can I use a double-sided floppy drive to image it? Or do I need to put the single-sided drive on my PC? Please, help! :) Thanks Alexandre --- Enviado do meu Apple IIGS (pq eu sou chique) Meu site: http://www.tabalabs.com.br Meu blog: http://tabajara-labs.blogspot.com

10 years, 12 months

Memory options for an HP 1000 (HP 21MX / 2112A)

by marc.verdiell＠gmail.com

My soon to arrive HP 2112 has a 2102A memory controller and 3x 2102A cards of 8k memory each. I suppose I could add more 2102As to fill it up the 5 remaining slots and bring it up to 64k. But the recently posted IO manual says it can support way more - up to 1.28M. I'm not sure yet how the HP 1000 memory works. Can I put larger (>8k) capacity HP 1000 memory boards in there to expand memory beyond 64k? Do I need to replace the memory controller with one that matches the larger capacity cards then? Marc

10 years, 12 months

UNIBUS extension card/cable sets

by jnc＠mercury.lcs.mit.edu

> From: Paul Koning >> Right, but the very similar QBUS does have terminations (of a sort - >> the rules for when you need terminations on QBUS extensions are so >> complex that I don't really grok them yet) 'in the middle' > That doesn't seem likely. ... the definition of 'termination' is > something that you learn in EE 101 and are unlikely to forget. I agree with your sentiments, _but_ all I know is that if you look at, e.g. the 1982 'microcomputers and memories' handbook, pg. 251, you'l see a three-backplane system, with terminations at the start _and_ end of the first backplane (and also at the end of the third backplane). I've seen other similar diagrams elsewhere, that's merely the first one I ran across in a quick search for this post. Like I said, I cheerfully admit that I don't really fully understand what's going on there in the analog domain, but I've seen this in more than one place in the DEC QBUS multi-backplane configuration instructions. Noel

10 years, 12 months

Transmission lines Was: UNIBUS extension card/cable sets

by jnc＠mercury.lcs.mit.edu

> From: John Wilson > I chose the digital version of EE as my major precisely because I knew > I'd flunk Fields and Waves. Transmission lines are black magic as far > as I'm concerned! I too have a hard time with analog in general, but transmission lines I seem to be OK with. The way I think about them is to model them as pipes, and the signal as a sound (single pulse) sent down the pipe. Proper termination is like a piece of cotton at the end of the pipe, it sucks up the sound and you don't get a reflection. If you just cap off the end of the pipe (i.e. no termination), the sound bounces, and you get an echo. So if you have a small un-terminated branch, part of the pulse bounces off the end, and comes back out, and then propogates both ways, so the original pulse gets a messy trailer tacked on the back of it. Etc, etc. I dunno how accurate this model of mine is, but it seems to work OK! :-) Noel

10 years, 12 months

organizing a trip to Cuba

by billdegnan＠gmail.com

http://millennialmainframer.com/2014/12/ibm-still-waiting-cuba-pay-mainfram… Who's up for it? B

10 years, 12 months

UNIBUS extension card/cable sets

by jnc＠mercury.lcs.mit.edu

> From: tony duell > There are 3 40 pin Berg headers, one row of each appears to be ground Ah, hadn't noticed that! But then again, I hadn't looked at them closely yet! :-) Yes, they do connect to ground - all the UNIBUS ground pins are ganged together, and connected to the A-row Berg pins on all 3 connectors. So every other wire on the 40-conductor flat cables should be ground - that's even better than the classic BC11A, where almost every other line is, from what I can see, simply left floating (which is better than nothing, but not as good as grounding them, is my understanding). >> I was wondering if maybe the M9015 was an M9014 with termination >> resistors, or something (the way the QBUS versions come with and with >> termination) > I would be very surprised. Unibus is normally terminated at the ends > and not in the middle. Right, but the very similar QBUS does have terminations (of a sort - the rules for when you need terminations on QBUS extensions are so complex that I don't really grok them yet) 'in the middle', so... I just couldn't find out _anything_ about M9015's, so I was just guessing in the dark. Real data gratefully received. > From: John Wilson > I was kind of assuming that there's some impedance-matching (etc.) > problem with using ribbon cables for more than one hop. Hmm. Well, I dunno; that may be beyond my (minimal :-) level of analog expertise. I would have assumed that it's the _change_ from one impedance level to another that's the issue (you can get a reflection off the junction), so whether one's using long or short cables between a pair of M9014's, it shouldn't be _that_ big a deal (modulo propagation delays, which _are_ an issue with length). Perhaps someone else can opine? But I hope we can do fairly long runs with the 40-conductor (aka BC05L-xx), that could save us when we run out of BC11A's, if that strange Flexprint flat white cable the BC11A uses is no longer available. Noel PS: From what I can see so far (done half the pins), the M9014 and M9042 do have an identical pinout on the Berg connectors.

10 years, 12 months

UNIBUS extension card/cable sets

by jnc＠mercury.lcs.mit.edu

> From: Alan Perry > FYI, in my 750, the UNIBUS expansion has a L0010 in the main cabinet > and a M9014 in the expansion cabinet. > From: tony duell > If it's any help I pulled an M9014 out of the Unibus Out slot of my > 11/730. There's currently an M9302 in there. Very interesting! Thanks for the data. This seems to indicate that the M9014 could function as either end of the cable. I was wondering if maybe the M9015 was an M9014 with termination resistors, or something (the way the QBUS versions come with and with termination), so I tried to find a picture of one, but... I can't even find a picture! Has anyone even seen an M9015? >> I see 'three' different kinds of 'UNIBUS to cables' cards listed: >> M9014 UNIBUS to 3 H854s >> M9015 3 H854s to UNIBUS >> M9031 UNIBUS to 3 3M cables for 11/74 >> M9042 UNIBUS to 3 H854, Dual So I have compared an M9014 and an M9042; the former is a 'normal' height dual module, the latter is a 'short' dual module. I suspect that they have the same pinout on the Berg headers; I tried a couple of UNIBUS signals, and they led to the same pin on the Bergs on the two different units. If and when I get energetic I will make a complete pinout list for the two units (I haven't been able to find any documentation on any of them online). Some day I'll even try joining a BA11 to an -11 with a pair of M9014's, and see if it does indeed work. Also, does anyone out there with an 11/70 know what the M9031 is used for? (I.e. does your system have one/more, and if so, where are they?) Noel

10 years, 12 months

cctalk Digest, Vol 12, Issue 5

by marc.verdiell＠gmail.com

Good info David. Thanks once more. ------------- "J. David Bryan" <jdbryan at acm.org> said: Subject: Re: HP 2113e Battery resistor >I might put NiMH batteries instead.... That may not be advisable, given the continuous constant-current trickle charger in the CPU power supply. The Panasonic "Nickel Metal Hydride Technical Handbook" recommends charging for no more than 10-20 hours, saying: "The overcharging of nickel-metal hydride batteries, even by trickle charging, causes a deterioration in the characteristics of the batteries. To prevent overcharging by trickle charging or any other charging method, the provision of a timer to regulate the total charging time is recommended." Panasonic's "Nickel Cadmium Batteries Technical Handbook," on the other hand, says explicitly that continuous trickle charging for Ni-Cds is a recommended charging method. -- Dave ------------

10 years, 12 months

George!

by COURYHOUSE＠aol.com

Great save! By the Way Evan I like the photo of that self contained Syston Donner Analogue computer in your book! Ed# _www.smecc.org_ (http://www.smecc.org) In a message dated 6/22/2015 1:01:29 P.M. US Mountain Standard Time, evan at snarc.net writes: Here's a new picture of "George" -- aka the Philbrick analog computer that MARCH rescued two months ago. It was used at M.I.T. from 1958-1970. http://snarc.net/george.jpg

10 years, 12 months

Strange DEC PC05 paper tape reader: doc for M705 needed

by j_hoppe＠t-online.de

Hi all, I could acquire *four* rotten PC05 Papertape Reader/Punches for PDP-11. I'm now restoring them. One of these is strange: Normally, the feed hole (between data hole 3 and 4) is used to clock in bits from the data holes. But this very special PC05 does not have a phototransistor for the feed hole, so the data clock signal must be generated by the stepper motor driver. Maybe it's a very old model: the READER CONTROL module is M705, not the usual M7050. And there's no doc for it. Does anybody has a FPMS with schematics for the M705 modul? Perhaps as part of some PDP-8 doc? Thanks, Joerg

10 years, 12 months

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