test-drb February 2015

test-drb@ccmp.vtda.org

203 participants
261 discussions

by jnc＠mercury.lcs.mit.edu

> From: Jacob Ritorto > Should I eliminate all this fancy bipolar and core memory and just use > an m7891? PS: I forgot to mention: that board, IIRC, _has_ to go into a Modified UNIBUS slot. Plugging it into something that's _not_ MUD will, I am pretty sure, fry something. Do you have a backplane with has MUD slots to plug it into? I _think_ DD11-C's and DD11-D's have them. > From: tony duell > A plain Variac does not provide isolation from the mains so you are > actually now working on mains-connected circuitry (read : dangerous and > you can't clip a 'scope on it). I'm clearly a little slow this morning: why can't you use a 'scope on it? > From: Mouse > Perhaps fortunately, it appears that here, at least, incandescents > aren't completely banned, just vanilla 100W ones. In the US, 'vanilla' 75W bulbs are now also banned (and I think 60W's are headed that way, too); 'specialty' bulbs (not sure of the exact definition - think coloured, etc) of 75W and 100W are still allowed. (As are, ironically, plain 150W and 200W!) Noel

9 years, 10 months

Prime?

by bbrown＠harpercollege.edu

I've heard something about a prime emulator (to run primos, premix etc).. does anyone know any info on where it is and how to get ahold of it? Anyone know of any actual prime hardware out there? Thank you! -Bob

9 years, 10 months

Heathkit H-8 Tape Sound Files?

by nf6x＠nf6x.net

Do any of y'all know of any archived tapes for the Heathkit H-8 computer that are online as audio files that I could record onto tapes, as opposed to image files containing the decoded data for use with emulators? So far, I've only found the latter, but would like to find the former for use with a real H-8. -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

9 years, 10 months

Differences between PDP-11/83-84 M8190-AB/AC and AD/AE CPU cards

by jnc＠mercury.lcs.mit.edu

So I've seen some references which say that the M8190-AB and -AC (w-o/w FPJ11 FPP chip) are 15 MHz "11/73" CPUs for QBUS use, and the M8190-AD and -AE (w-o/w FPJ11) are 18 MHz "11/83-84" CPUs for UNIBUS use (via the KTJ11-B convertor, of course). (Of course, the /83 is nominally QBUS, but let's ignore that for the moment... :-) (And I'm not even going to try to give the KDJ11- suffixes that go with these... :-) However, I'm wondering if this is correct... I have a CPU board out of a 11/84 (one owned by DEC, no less!) which says M8190-AB on the handles, but the clock crystal says "18.432", and it has a 57-19400-09 J11 chip, which seems to be the 18MHz version (the 15Mhz seems to be -04). Comparing it to a 'stock' -AB, this one seems to have the same 74S472 PROMs (6 along the lower left-hand edge), PALs (top center and lower left), etc. But they also match the ones on a 'stock' -AE, too! So clearly an -AB/AC _can_ be _upgraded_ to an -AD/-AE... but are there actually any differences between an -AB/AC and an -AD/-AE, other than the speed? I don't have my /84 up yet, so I can't plug a stock -AB in and see if it works, but I'm starting to get the impression that except for the speed of the J11 (and the crystal), and whether or not it came with the FPJ11, all four of these boards are otherwise identical. Whether it's a 73, 83 or 84 depends entirely on whether it has PMI memory and the KTJ11-B UNIBUS converter (and the correct backplane, for the latter, of course). Anyone have an confirmation one way or the other? Thanks! Noel

9 years, 10 months

11/23 clock issue

by jnc＠mercury.lcs.mit.edu

So I'm debugging a dead PDP-11/23 board (M8186). The first thing I check is the clock; specifically the output of the first stage buffer-inverter (pin 16 of E4, a 74S240, upper right corner of page 2 of the prints), which is distributed to a number of places. Nada. Totally flat-lined. So I checked the input (pin 4), and it's sitting at about 2V. Also flat-lined. This does not seem good... :-) So here's my question: what's the likely fault here? The only thing upstream of that gate is the 13MHz crystal itself. So the fault has to be either the crystal or the S240 (which seems to be some sort of octal 3-state inverting buffer). Any guesses as to which? As usual, thanks in advance for any help! Noel

9 years, 10 months

It's time to restore the 11/45.

by jnc＠mercury.lcs.mit.edu

> From: Jon Elson > there is no part of the EUT that is at neutral potential > From: tony duell > With most 'scopes one side of the input is grounded -- you have a > coaxial cable with the shield connected to the 'scope case and true > ground. Ah. That's the part I was missing! I (naively :-) assumed that the 'scope's whole input amplifier would be 'floating', and the input signal would be taken as referenced to the 'ground' on the probe, which could itself be floating. Clearly not! (I'll have to look at the manuals/prints for my 'scopes - Tektronix 465's - to see if they are this way. Anyone happen to know, offhand?) Thanks! > In most, if not all, countries, one side of the mains is connected to > ground too. Yes, in the US that's code; neutral (aka 'return') is usually tied to ground at the main panel. (Well, at least in the state I live in - technically I suspect that it's under state law, not Federal, but I would assume the states are all the same, the way they are with commercial law.) Noel

9 years, 10 months

It's time to restore the 11/45.

by jnc＠mercury.lcs.mit.edu

> From: Jon Elson > Gee, our 11/45 (SN343) didn't have this, as far as I know. > This sounds more like an 11/70. Similar to the 11/70 in some ways, yes (a high-speed private memory bus), but very different in others (a second UNIBUS allowing another PDP-11 access to shared memory - nothing like that on the 11/70). Like I said, this is in the 1971 11/45 Processor Handbook (which I think is the first edition; I've never seen an earlier one), so I think it's original. I guess that manual's not online; if you'd like, I can scan that diagram and put it online. Noel

9 years, 10 months

MicroVAX 2000 with Network Interfaces problems.

by mattislind＠gmail.com

I have a MicroVAX 2000 that has suffered from a leaking battery. It has been cleaned and seems to be mostly working except for the network interface. The startup reports ?? NI 0011.700E V1.1 for the network interface. The switch is set for thin ethernet, and a 50 ohm T is in the connector with two terminators. What does the failure code mean? I cannot find any document identifying different failure codes. It seems that the software finds the version so at least something is working. Anyone that has an idea what is wrong? I will try to examine the content of registers at 200E0000 and 200E0004 and also if the ROM is accessible properly at 20100000 - 2011FFFF. But other than that, what can be done?

9 years, 10 months

It's time to restore the 11/45.

by jnc＠mercury.lcs.mit.edu

> From: Jacob Ritorto > Should I eliminate all this fancy bipolar and core memory and just use > an m7891? PPS: Why bother with memory at all, at least to get the CPU running at a basic level? Use the hack that someone here (I forget who, IIRC it was Johnny B.) reported, which is that you can store really small programs in the PARs - although in the 11/45, you're restricted to instructions of the form 00xxxx! Still, that's good enough for BR, CLR, INC, etc, etc. Noel

9 years, 10 months

Weekly Classic Computer Trivia Question (20150204)

by dpi＠dustyoldcomputers.com

This time lets refer to some classic fictional computers used in movies. Everyone probably knows about the HAL 9000 used in the movie 2001 a Space Odyssey. What was the name of HAL's sister computer in the movie 2010 Odyssey two? That was a warm up question. This one should be more difficult. What was the designation of the computer in the movie WarGames and what does it mean? And finally, As silly as it was the movie Hackers referred to the mainframe computer in the movie as a Gibson. Where did the term Gibson come from? -- Doug Ingraham PDP-8 SN 1175

9 years, 10 months

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test-drb February 2015