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  • daver2's Avatar
    Today, 09:53 AM
    daver2 replied to a thread Epson Fx86e in CP/M and MP/M
    I would wait for BUSY=0 and /ACK=1 (as you are doing at the moment). Next, send the desired data byte out and wait for 0.5 us (data setup time). ...
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    15 replies | 201 view(s)
  • daver2's Avatar
    Today, 09:41 AM
    daver2 replied to a thread RX02 for QUniBone is ready ... now media questions in DEC
    Thanks Al. I will have a look. Hopefully, that will save some time and hassle! Dave
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    5 replies | 87 view(s)
  • daver2's Avatar
    Today, 06:12 AM
    daver2 replied to a thread RX02 for QUniBone is ready ... now media questions in DEC
    >>> Also I played with UCSD Pascal on an Apple II recently. Cool stuff! >>> I learned LSI11 was the devleopment machine for it. >>> Any pointers to...
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    5 replies | 87 view(s)
  • daver2's Avatar
    Today, 03:05 AM
    daver2 replied to a thread Epson Fx86e in CP/M and MP/M
    The manual states CR, but you will still need to output a LF yourself (unless you have the appropriate DIP switch set). Check the words in Appendix A...
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    15 replies | 201 view(s)
  • daver2's Avatar
    March 2nd, 2021, 11:04 AM
    daver2 replied to a thread What did I do to my PDP-8 today. in DEC
    That’s one of the references I was trying to find. I suspect the voltage will fall not rise if the capacitor fails open circuit though. Dave
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    224 replies | 15643 view(s)
  • daver2's Avatar
    March 2nd, 2021, 07:05 AM
    daver2 replied to a thread What did I do to my PDP-8 today. in DEC
    Tom, My guess about the isolated transformer secondary and capacitor would be a harmonic filter of some description. If the capacitor goes...
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    224 replies | 15643 view(s)
  • daver2's Avatar
    February 28th, 2021, 02:19 PM
    daver2 replied to a thread PDP-8 core memory troubleshooting in DEC
    No, I haven’t tried this procedure before. I am just thinking out of the box :-)! It is good that you are seeing some coupling though. I do...
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    74 replies | 4837 view(s)
  • daver2's Avatar
    February 28th, 2021, 02:34 AM
    daver2 replied to a thread Memory problem with PET 2001 in Commodore
    Yes, address $0000 looks fine. However, the interesting thing would be address $0001 (as stated back in post #164). The fact that the machine...
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    177 replies | 6798 view(s)
  • daver2's Avatar
    February 25th, 2021, 07:56 AM
    daver2 replied to a thread Cbm 8050 dual drive in Commodore
    Hello again Ilpaninaro. When you say "works fine" do you mean it powers up and the green light comes on only? This is an indication that the...
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    3 replies | 107 view(s)
  • daver2's Avatar
    February 24th, 2021, 02:01 AM
    daver2 replied to a thread Hi, I am Dalmas. in Introductions
    I have been able to find the schematics for the SIM4-01 and -02 but not the -03. If they don't exist online, could I ask that you preserve them...
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    11 replies | 225 view(s)
  • daver2's Avatar
    February 24th, 2021, 12:22 AM
    daver2 replied to a thread Dick Monahan has found VCF in Introductions
    Welcome. We are a global mix of both hardware and software. Plenty of people here that would welcome a new member! I am a member of a...
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    3 replies | 126 view(s)
  • daver2's Avatar
    February 24th, 2021, 12:12 AM
    daver2 replied to a thread Hi, I am Dalmas. in Introductions
    Welcome to VCFED... Nice little card you have there. Let me get back to you presently about how much of a SIM4-03 you can test without a...
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    11 replies | 225 view(s)
  • daver2's Avatar
    February 23rd, 2021, 11:09 AM
    daver2 replied to a thread PET 2001 Cover? in Commodore
    There may be a small market for these types of covers of course... Dave
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    3 replies | 97 view(s)
  • daver2's Avatar
    February 21st, 2021, 08:07 AM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    Thanks Jos, I will add some of my microcode logic diagnostic code to the specific addresses around where it is playing with these locations to see...
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    264 replies | 31531 view(s)
  • daver2's Avatar
    February 21st, 2021, 07:07 AM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    I think (:-)) I have put all of the infrastructure back in for interrupts now... I had to remove all of my diagnostic code within the I/O reads...
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    264 replies | 31531 view(s)
  • daver2's Avatar
    February 21st, 2021, 06:26 AM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    It looks like the write to ROM from the microcode is intentional (unless I have misunderstood the I/D logic somewhere - which wouldn't surprise me of...
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    264 replies | 31531 view(s)
  • daver2's Avatar
    February 21st, 2021, 03:54 AM
    daver2 replied to a thread Memory problem with PET 2001 in Commodore
    The timing should be locked to a clock pulse (one of the 8 phases) and not left to the whim of a gate delay or pull-down capability. At that...
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    177 replies | 6798 view(s)
  • daver2's Avatar
    February 21st, 2021, 02:27 AM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    Hi Monty, Yep, I have that document. This is a listing of the microcode not the firmware itself. It passes the 4052/4054 determination OK...
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    264 replies | 31531 view(s)
  • daver2's Avatar
    February 21st, 2021, 01:26 AM
    daver2 replied to a thread Memory problem with PET 2001 in Commodore
    >>> I know Dave doesn't like swapping stuff randomly, but It worked, so I would take it! Good to see that it passes my PETTESTER code (that...
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    177 replies | 6798 view(s)
  • daver2's Avatar
    February 20th, 2021, 04:24 PM
    daver2 replied to a thread Tek 405x web-browser emulator in Other
    Hi Monty, Yes and no... I keep having a go. I get a bit further and then hit a problem and get distracted by real paying work! I then go...
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    264 replies | 31531 view(s)
  • daver2's Avatar
    February 20th, 2021, 05:57 AM
    daver2 replied to a thread Tandy 1000 RL tone of death in Tandy/Radio Shack
    yep, classic short circuit tantalum capacitor across the power rails by the looks of it. Once it has gone short circuit, it takes the voltage down...
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    15 replies | 408 view(s)
  • daver2's Avatar
    February 19th, 2021, 01:20 PM
    daver2 replied to a thread Floppy disk interwseave and SYSTEM load time in CP/M and MP/M
    Chuck, That’s a nice description and avoids the ‘lazy write’ issue. Dave
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    46 replies | 759 view(s)
  • daver2's Avatar
    February 19th, 2021, 11:04 AM
    daver2 replied to a thread PDP11 GUI Crash in DEC
    I am guessing that a new build of PDP11 GUI is going to be required. Either because Microsoft have 'retired' a function or that the parameters have...
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    6 replies | 307 view(s)
  • daver2's Avatar
    February 19th, 2021, 02:31 AM
    daver2 replied to a thread Memory problem with PET 2001 in Commodore
    You need about 10 posts... From the trace back in post #123 I think we concluded that address $0000 was OK and things started to fail at address...
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    177 replies | 6798 view(s)
  • daver2's Avatar
    February 18th, 2021, 01:16 PM
    daver2 replied to a thread Memory problem with PET 2001 in Commodore
    Sorry guys, I got sidetracked with real work today. I had a quick look this morning, and then the problems started that demanded my attention. I...
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    177 replies | 6798 view(s)
  • daver2's Avatar
    February 18th, 2021, 05:51 AM
    daver2 replied to a thread PETunia's Repair Log in Commodore
    There is a schematic around - but it may be in one of the other Zimmers directories - and the transformer fitted may be different to the schematic...
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    173 replies | 10932 view(s)
  • daver2's Avatar
    February 17th, 2021, 01:58 PM
    daver2 replied to a thread Partial Altair Kit I Bought in S-100
    That sounds like the logical approach! Buy what you really want to keep that interests you when it appears for 'sensible money' - and sell off...
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    11 replies | 400 view(s)
  • daver2's Avatar
    February 17th, 2021, 12:46 PM
    daver2 replied to a thread Partial Altair Kit I Bought in S-100
    And I thought you said your collection was large enough now? Does that mean you are going to start selling things off and replacing them with...
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    11 replies | 400 view(s)
  • daver2's Avatar
    February 17th, 2021, 05:49 AM
    daver2 replied to a thread Memory problem with PET 2001 in Commodore
    Yes, weird... >>> I lose track... which memory location is currently being tested? That's why I am interested on the previous WRITE cycle. ...
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    177 replies | 6798 view(s)
  • daver2's Avatar
    February 17th, 2021, 02:10 AM
    daver2 replied to a thread Floppy disk interwseave and SYSTEM load time in CP/M and MP/M
    Mike, good thinking about the difference between the BDOS and COLD loader... Dave
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    46 replies | 759 view(s)
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SW/HW design engineer

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