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  • daver2's Avatar
    Today, 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 | 4725 view(s)
  • daver2's Avatar
    Today, 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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    174 replies | 6384 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 | 76 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 | 134 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 | 111 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 | 134 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 | 76 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 | 31342 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 | 31342 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 | 31342 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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    174 replies | 6384 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 | 31342 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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    174 replies | 6384 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 | 31342 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 | 331 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 | 681 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 | 279 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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    174 replies | 6384 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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    174 replies | 6384 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 | 10756 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 | 354 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 | 354 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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    174 replies | 6384 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 | 681 view(s)
  • daver2's Avatar
    February 17th, 2021, 02:01 AM
    daver2 replied to a thread Memory problem with PET 2001 in Commodore
    Hi Greg, Thanks for the update. FA0 (for the refresh) is generated from RA7 (sourced from schematic sheet 8) and is a lower frequency than...
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    174 replies | 6384 view(s)
  • daver2's Avatar
    February 16th, 2021, 02:20 PM
    daver2 replied to a thread Floppy disk interwseave and SYSTEM load time in CP/M and MP/M
    Mike, There are two (2) ways of achieving the same result: physical and logical. If the physical arrangement of sectors is 1,2,3,4,... on the...
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    46 replies | 681 view(s)
  • daver2's Avatar
    February 16th, 2021, 12:07 PM
    daver2 replied to a thread Floppy disk interwseave and SYSTEM load time in CP/M and MP/M
    SECTRAN is a BIOS entry point to permit CP/M 2 to perform software sector translation (as has been stated above). If you are going to implement...
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    46 replies | 681 view(s)
  • daver2's Avatar
    February 14th, 2021, 03:35 PM
    daver2 replied to a thread Tandy 1000 RL tone of death in Tandy/Radio Shack
    The first thing is to use your eyes and nose and look / smell for the dead components... We can take it from there... My guess would be a RIFA...
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    15 replies | 331 view(s)
  • daver2's Avatar
    February 14th, 2021, 11:22 AM
    daver2 replied to a thread Teletype to linux in DEC
    The sound of a happy teletype :-)... Well done. Dave
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    12 replies | 364 view(s)
  • daver2's Avatar
    February 14th, 2021, 11:18 AM
    daver2 replied to a thread Model 1 Startup Screen in Tandy/Radio Shack
    Yes, there are. In fact, pins 2, 4, 6 and 10 of both of them should all be high. Probably worth checking while you are at it. Can you also...
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    8 replies | 139 view(s)
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SW/HW design engineer

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