test-drb March 2014

test-drb@ccmp.vtda.org

175 participants
175 discussions

by rickb＠bensene.com

> Paul Anderson wrote: > It probably doesn't matter that much, but I meant take it to the bare > minimum- no EAE, no timeshare, 4K only, etc. Sorry it didn't help. No worries -- I appreciate the input! I did think that you meant stripping it down to the bare minimum, but having OS8 running makes loading the diags and testing much easier and faster -- and all that needs 8K, Mem Ext/Timeshare, and the RX8E. I don't want to remove the EAE..I just am scared of messing with the CPU stack. At least I was able to eliminate the high speed paper tape interface, the MOS RAM, and the second serial port, and get it all down to one Omnibus, which is a step in the right direction. I could strip it down to the bare, but then I'd be fussing with loading RIM, and then BIN, then pushing papertape images of the diags to the machine over serial -- it's just tedious and slow. I may give this a try later, but in light of the information below, I will probably try something else before I strip it bare. I just now put the machine back to the original configuration, and nothing changed -- the problematic behavior with the RK8E still exists. David Humphries had mentioned in a posting here that he had observed a transient on a signal related to loading the current address register in his RK8E that exhibited similar symptoms to mine. While I didn't know the specific signals that David was scoping, I guessed, from looking at the schematics, that perhaps he was monitoring the LOAD and CLK signals that drive the three 74161 counter ICs on the M7105 board that make up the Current Address Register. So, while putting the system back to its original configuration, I tacked in wire extensions to the LOAD and CLK pins of one of the 74161s to bring them out so I could scope them. Since the M7105 board is the middle board of the three-board RK8E sandwich, the only way to get access to the signals is use wire extensions. Once I got the system put back together, I toggled in a small program to repeatedly load the current address register in the RK8E with zero, e.g.,: 0200 7200 CLA CLL 0201 6744 DLCA 0202 5200 JMP 0200 I started this program running and watched the scope. There is a definite spike showing up on the CLK line. This spike could indeed cause the counter to increment after the initial address is loaded into the counter using the 6744 IOT (Load Current Address Register). The photo of the scope traces I observed is posted here: http://pail.bensene.com/RK8ESpike.jpg The top trace is the LOAD signal, and the bottom trace is the CLK signal. The negative-going spike on the CLK line is clearly obvious. The traces look quite similar to the scope image that David posted. I am hoping that David will read this and find his notes on what he did to fix the issue (installing a 7474 flip flop somewhere to eliminate the spike) and post it so I can make a similar modification and see if it fixes my problem. It isn't intuitively obvious to me where a flip flop/latch tacked into the logic would get rid of the spike. It's my hope that this is what is going on, and that David's fix will fix my RK8E/RK05 problems. Rick Bensene

10 years, 9 months

Fwd: [rescue] RT-11 manuals, VAX manuals, AUI for pickup

by jim＠deitygraveyard.com

John has had problems getting on the list and so has asked me to forward this on. Please reply directly to him at john at jfloren.net . Jim ---------- Forwarded message ---------- From: John Floren <john at jfloren.net> Date: Tue, Feb 25, 2014 at 2:48 AM Subject: [rescue] RT-11 manuals, VAX manuals, AUI for pickup To: The Rescue List <rescue at sunhelp.org> I'm cleaning out the closets and I've found a bunch of stuff that I never look at, so anyone in the Bay Area can come get: * 4 big binders of RT-11 documentation (operation manual, utilities, programming, application files) * About a dozen Sony QD-600A tapes * A whole load of VAX, VMS, and PDP-11 books from DEC * A bunch of AUI-twisted pair boxes, one AUI-thinnet box, and some AUI cables. Please please PLEASE come take all of it at once! The whole load will fit in a single car trip. I'm in Livermore. john

10 years, 9 months

Wanted: 5.25" 40t drive / 5.25" HD media

by jules.richardson99＠gmail.com

Morning all... I'm in need of a 5.25" 40-track double-sided floppy drive (i.e. the venerable "360K" in PC parlance), preferably one with direct drive to the spindle so I don't have to worry about worn drive belts. Bezel color, height etc. unimportant, I just want a 40t unit to hang permanently off my desktop PC, as hauling one out of my vintage machines every time I want to write to a disk from there gets old fast. I could also use ten or so *HD* 5.25" floppies so I can get my Compaq 286 and the pair of Compaq luggables at the local science museum up and running - I've exhausted all of the local sources that I can think of. I don't necessarily need new-in-box or anything, but of course error-free would be good :-) Anyone got anything they'd be willing to part with? (I'm in the northern US) [Also, I don't see many wanted ads on the list, although as far as I know they're not frowned upon - apologies if they are!] cheers, Jules

10 years, 9 months

PDP-8 27-Bit Floating Point Package Listing/Source Needed

by bobvines00＠gmail.com

Does anyone have the documentation, particularly the listing (or source), for the DEC-08-NFPEA-A-PB (1972-05-26) 27-Bit Floating Point Package? Thanks, Bob

10 years, 9 months

altair tapes

by ball.of.john＠gmail.com

>apears a vtr machean has come up with tapes on programes ur altair anyone >interested in it noticed it on my local buy and sell site >http://www.kijiji.ca/v-electronics/winnipeg/panasonic-vtr-nv-3020-with-15-r eels/539056526?enableSearchNavigationFlag=true For $40 I would totally digitize those tapes and upload them somewhere. Shoot, I would buy it so I have the recorder to go with my Panasonic camera. Unfortunately I'm about 3000km west of the listing.... -John

10 years, 9 months

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test-drb March 2014