test-drb January 2015

test-drb@ccmp.vtda.org

175 participants
253 discussions

by lproven＠gmail.com

Maker describes it as a cross between a C64 and an HX-20. http://www.grappendorf.net/projects/6502-home-computer -- Liam Proven ? Profile: http://lproven.livejournal.com/profile Email: lproven at cix.co.uk ? GMail/G+/Twitter/Flickr/Facebook: lproven MSN: lproven at hotmail.com ? Skype/AIM/Yahoo/LinkedIn: liamproven Cell/Mobiles: +44 7939-087884 (UK) ? +420 702 829 053 (?R)

9 years, 11 months

MSV11-D debugging question

by jnc＠mercury.lcs.mit.edu

OK, so I'm back to debugging busted memory cards. Again, I have a sitation where a bit is stuck on, and I'm curious to see if anyone has any insight into which chip (of 3) might be causing it (in an attempt to not have to try replacing them at random :-). Looking at the line from the memory chips (two chips - E26 and E27, if anyone cares - have outputs wire-or'd together) to the input of an octal tri-state latch (E40, an S373), that line goes to about +2V when the machine is powered on (which is similar to what other bits do); then, when I run a two-instruction read loop, (after writing 0 into that location), the line goes to +5V and stays there (which is distinctly unlike how other bits behave). Any guesses as to whether the culprit is the S373 or one of the memory chips? Noel

9 years, 11 months

Digital PDP11/10 PDP 11/20 Price List Dec 15, 1969

by jnc＠mercury.lcs.mit.edu

> From: B Degnan > there was a "rev 1" PDP11/10 that was used as a process control system. > You could buy the 11/20 version that had the front panel. Otherwise > they were very similar/same systems. According to my 1971 11/20-15-R20 handbook, the 11/15 (the 'rev 1' 11/10, KC11 processor) did have one significant difference from the 11/20, which is that it only supported one interrupt level, instead of four (see table pg. 2). I seem to recall reading that in other places, too. Of course, according to that table, the 11/05 (KD11-B) also only supported one interrupt level, so maybe that table is confused. Noel

9 years, 11 months

ANSWER: Weekly Classic Computer Trivia Question (20150121)

by dpi＠dustyoldcomputers.com

And this question must have been too obscure to elicit any response. The answer is C) 50. After posting the trivia question I came up with a way on the PDP8 to measure time events to a resolution of 1.5 microseconds and went back and retested the High Speed Paper tape reader hardware. The earlier version could only measure to 3.0 microseconds resolution. Here is the 1.5 microsecond version of the program: / ADVANCED HIGH SPEED PAPER TAPE TIMING PROGRAM / / USES FIELD 1 AND LINK/AC TO MEASURE TIME DELAY / WITH INTERRUPTS. *0000 .-. / INTERRUPT ENTRY POINT RSF / MAKE CERTAIN IT WAS A HSR INTERRUPT HLT / HOUSTON WE HAVE A PROBLEM DCA I AUTO0 / SAVE COUNT AND LINK AS A 24 BIT RAL DCA I AUTO0 / SAVE LINK JMP MORE *0010 AUTO0, .-. / MORE, ISZ Z FRM1 / CHECK FOR DONE JMP NEXT / EXIT INTERRUPT AND CONTINUE TIMING TAD Z COUNTS / POINT AT START OF ARRAY DCA Z AUTO0 TAD Z CNTS / GET BACK ORIGINAL COUNT OF SAMPLES DCA Z FRM1 TLS / PRIME THE PUMP PRLP, TAD I Z AUTO0 / GET 12 BIT PART DCA Z BASE TAD I Z AUTO0 / GET LINK PART CLL RAR / RESTORE THE LINK TAD Z BASE / COUNT IS IN LINK AND AC TAD Z C0002 / ADD 2 WHICH CORRECTS TIMING FOR START DELAY DCA Z BASE / SAVE FOR PRINTING RAL / PRINT THE LEADING OCTAL DIGIT TAD Z CHZERO / ADD IN '0' TO GET LEADING DIGIT JMS PRINT / AND WE DONT HAVE TO WORRY ABOUT THE LINK ANYMORE TAD Z M0004 / INITIALIZE DIGIT COUNTER DCA Z DIGCNT DIGLP, TAD Z BASE / OCTAL DIGIT IS IN UPPER 3 BITS RTL RAL DCA Z BASE / NEXT DIGIT IS IN UPPER 3 BITS TAD Z BASE / NEED TO SHIFT ONCE MORE TO GET IN LOWER 3 BITS RAL AND Z C0007 / KEEP JUST THE LOWER 3 BITS TAD Z CHZERO / ADD IN THE OFFSET FOR ASCII 0 CHARACTER JMS PRINT / AND GO PRINT IT ISZ Z DIGCNT JMP DIGLP TAD Z CHSPC / PRINT A SPACE JMS PRINT TAD Z CHCR / PRINT CR JMS PRINT TAD Z CHLF / PRINT LF JMS PRINT ISZ Z FRM1 / ARE WE DONE? JMP PRLP / NO HLT / ALL DONE JMP START / GO AGAIN NEXT, CLA CLL / LINK AND AC MAKE A 13 BIT COUNTER ION / INTERRUPTS ON. CIF THAT FOLLOWS DELAYS THIS CIF 10 / SWITCH TO FIELD 1 AT THE JMP I CZERO RFC / START THE NEXT READ JMP I C0000 / START COUNTING (ADDS 2 TO THE ACTUAL COUNT) PRINT, .-. / PRINT THE CHARACTER IN THE AC TSF / WAIT FOR LAST CHARACTER TO FINISH PRINTING JMP .-1 / WAIT TLS / SHIP IT CLA CLL / RETURN WITH AC CLEAR JMP I PRINT / RETURN / CONSTANTS C0000, 0 C0002, 2 C0007, 0007 / MASK CIAC, IAC / IAC CONSTANT CHLF, 0012 / CONSTANT FOR LINE FEED CHCR, 0015 / CONSTANT FOR CARRIAGE RETURN CHSPC, 0040 / CONSTANT FOR A SPACE CHARACTER CHZERO, 0260 / CONSTANT FOR '0' CHARACTER COUNTS, ARRAY-1 / POINTER TO COUNTS ARRAY-1 FOR AUTO INCREMENT INITIALIZE M0004, -4 / VARIABLES FRM1, 0000 / FRAME COUNT KEPT HERE CNTS, 0000 / COPY OF FRAME COUNT READ FROM SWITCHES BASE, 0000 / TEMPORARY STORAGE OF WORD BEING PRINTED DIGCNT, 0000 / COUNT OF DIGITS WHEN PRINTING *0200 START, CLA DCA FRM1 / FILL ALL OF FIELD 1 WITH IAC INSTRUCTIONS CDF 10 FILL, TAD CIAC / GET THE CIAC INSTRUCTION DCA I FRM1 / PUT IT ON FIELD 1 ISZ FRM1 / BUMP AND CHECK FOR DONE JMP FILL / NOT DONE CDF 00 / RESTORE TO FIELD ZERO AGAIN, LAS / READ SR CMA / INITIALIZE FRAME COUNT FROM SR FOR ISZ DCA Z FRM1 TAD Z FRM1 DCA Z CNTS / KEEP A COPY FOR USE WHEN PRINTING TAD Z COUNTS / INITIALIZE THE AUTO INCREMENT REGISTER DCA Z AUTO0 JMP NEXT / AND GO MAKE A PASS *0400 ARRAY, .-. /STORE THE COUNTS HERE $ The program fills field 1 with IAC instructions and then reads the switch register to find out how many frames to process. Each frame is timed and the result stored in words pairs starting at 0400. Counts are 0-8191 which on a straight 8 would represent 0 - 12286.5 microseconds. The actual time is 2 counts more than this because of the JMP I C0000 to switch fields and start execution of the timer. Once the switch register count of frames is reached the contents of the array plus 2 is dumped out as 5 octal digits to the teletype. In the case of the Type 750 and PC01 the first character read sets the flag immediately so the first entry in the table shows as 2 which for the purpose of my emulator I fixed the first entry. My emulator of course gives the same answers as the 8 but then it has to because it uses the table generated by the real 8. The only other place I ran it was on Sim8 which always gives 0145 as the answer which is not even close. I will come up with something of more general interest for the next trivia question. I have something in mind already. Doug Ingraham PDP-8 S/N 1175 On Wed, Jan 21, 2015 at 11:27 PM, Doug Ingraham <dpi at dustyoldcomputers.com> wrote: > Many of us on this list are collectors of one sort of computer or > another. I don't think of myself as a collector so much as a caretaker of > my PDP-8. Of the things it has been fairly easy to get in recent years are > the CPU and its related cards for the models that were produced in fairly > large numbers. What is not easy to get are peripherals for these > machines. So here is a question relating to the Type 750 high speed paper > tape reader found on the early models. A few years back we were working on > getting the CPU back in good working order. We needed to read in the > diagnostic paper tapes but the reader was not reliable. Went through the > tuning procedure and found that it was trying to read the tape at nearly > 450 cps. After tuning it up the full speed now sits at 342 cps. > > The question is how many frames does it have to read before it reaches > full speed? > > A) 1 > B) 10 > C) 50 > D) 100 > > This is probably a somewhat squishy number and would depend somewhat on > tuning. I wrote a couple of programs to determine this so I could add > correct delays to my emulator. I was able to obtain a 3 microsecond > resolution count of the delay. How that was accomplished might make for > another trivia question. > > > > > -- Doug Ingraham PDP-8 SN 1175

9 years, 11 months

RA81 removal

by jnc＠mercury.lcs.mit.edu

> From: Johnny Billquist > If that was the case, then the previous user was sloppy. In addition to > that latch, you are also supposed to screw in four (I think it is) > screws from the rail to the drive there too. Yup, manual confirms 4. Anyway, maybe that's why they got rid of that feature on the RA81 - people were being lazy and depending on the latches, and not putting in the screws. Noel

9 years, 11 months

RA81 removal

by jnc＠mercury.lcs.mit.edu

> From: Johnny Billquist > You are supposed to remove the two tiny screws that holds the slide to > the drive when you remove it. Yeah, that seems to be the conclusion. What's odd is that RL0x's use almost identical (maybe they are identical) slides, but on the RLOx's, there _is_ (I think) a way to take the drive out without undoing screws; there's a little latch at the very front of the slide, and it looks like if one trips that latch, the rail along the side of the drive case will slide out out of the slides. I wonder why they didn't do that on the RA8x's as well? Maybe because those weigh so much more? Noel

9 years, 11 months

RA81 removal

by jnc＠mercury.lcs.mit.edu

> From: Johnny Billquist > you then have some additional small locks and tricks if you want to > extend them beyond their normal point, as needed if you actually plan > to remove them from the slides. Sorry, I was not clear enough: that is exactly what I want to do - remove them from their slides (i.e. from the cabinet). I do know how to do that by taking out the two machine screws in each side which secure the slides to the disk case. However, is there some way to remove the drive completely, without doing that? I.e. a way to separate the slide into two parts, one of which stays with the cabinet, and one with the disk drive? Noel

9 years, 11 months

Digital PDP11/10 PDP 11/20 Price List Dec 15, 1969

by billdeg＠buzz1.com

I scanned some info on the launch of the Digital PDP11. As the documents show, there was a "rev 1" PDP11/10 that was used as a process control system. You could buy the 11/20 version that had the front panel. Otherwise they were very similar/same systems. The "rev 2" PDP11/10 is the unit most people are more familiar with, the core system is interchangeable with the 11/05. Most references I have seen on the WWW do not include the original PDP11/10, anyone have one? http://vintagecomputer.org/browse_thread.cfm?id=593 Bill

9 years, 11 months

RA81 removal

by jnc＠mercury.lcs.mit.edu

> From: Johnny Billquist > You mean sliding them out on their rails or removing them from the > rails? Sliding them out on their rails. (Removing them from their rails I've figured out how to do! :-) Noel

9 years, 11 months

found a 1702

by dgriffi＠cs.csubak.edu

I found a 1702 EPROM rattling around in the bottom of one of my boxes of stuff. I have no idea what's on it. Can someone give me some advice on just reading the thing with a TL866? If/when I decide I want to program it, I'll make something like this: http://www.tronola.com/html/1702a_prom_programmer.html -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

9 years, 11 months

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test-drb January 2015