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  1. Can I bump this thread and see if anyone has...

    Can I bump this thread and see if anyone has found either documentation or media for MicroPower/PASCAL in the intervening time please?

    Cheers,

    Dave
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    I was debugging the darn things just before the...

    I was debugging the darn things just before the lockdown!

    In fact, I should be up at your end of the world now...

    Yes, USB serial things are not really 'true' RS232. Although the signal levels...
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    This looks like a 'non-standard' CPM modification...

    This looks like a 'non-standard' CPM modification to me.

    IC45 will be required as it interfaces the NAS-SYS and BASIC ROMS to the CPU along with any of the local on-board RAM/EPROM devices. Some...
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    Forgot about the ‘D’ input being grounded, so...

    Forgot about the ‘D’ input being grounded, so yes, only 0..7 and the digit not being enabled at all to give us the blank.

    Always better to ‘debunk’ with evidence rather than just stating ”April...
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    The description of the 'older' card is here...

    The description of the 'older' card is here http://www.bitsavers.org/pdf/dec/pdp11/1134/KY11-LB_MaintMan.pdf along with the 8008 firmware listing.

    The schematics of the older and newer cards are...
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    On both variants of M7859 card the seven segment...

    On both variants of M7859 card the seven segment LED displays are driven by an SN7447A BCD to 7-segment driver IC.

    Looking up the Texas Instruments datasheet for this device indicates that the...
  7. Found this: ...

    Found this:

    http://bitsavers.trailing-edge.com/pdf/dec/pdp11/handbooks/PDP11_Software_Handbook_1978.pdf

    Page 6 onwards identifies which hardware can run which O/S.

    Not much - but it's a...
  8. I do remember seeing in the documentation for the...

    I do remember seeing in the documentation for the various PDP machines that we bought a list of 'officially supported' DEC Operating Systems and software. I haven't got a concrete document I can...
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    You can never go wrong with space invaders! ...

    You can never go wrong with space invaders!

    Nice job!

    Dave
  10. That's exactly what the website referenced in...

    That's exactly what the website referenced in post #2 states for a 1640 like yours:

    "On the 1640, 2086, 3086 and 5086, you will need to upgrade the processor from an 8086 to a V30 to get the...
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    Yes, you don't want to go connecting that pin to...

    Yes, you don't want to go connecting that pin to GND without a good reason :-). As Dwight correctly states, that pin being low prevents the CPU from reading the contents of the video RAM. No wonder...
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    If the characters are ALL displayed correctly on...

    If the characters are ALL displayed correctly on the screen this means that the CPU can correctly write to the video RAM (and the results are correctly displayed) - but it is likely that the CPU is...
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    Texas Instruments have an excellent article on...

    Texas Instruments have an excellent article on this very subject.

    In general NEVER connect an input DIRECTLY to VCC/+5V. Some families of TTL are fine, others will work, but could destroy the IC...
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    Yes, we would need to know exactly what your...

    Yes, we would need to know exactly what your modification was to advise you.

    Dave
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    This all smells as fishy as a John West Tuna Bath...

    This all smells as fishy as a John West Tuna Bath to me!

    Dave
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    Good going! Chalk another one up to the...

    Good going!

    Chalk another one up to the PETTESTER... That problem would have been a ***** to find otherwise...

    Dave
  17. I am hoping to resurrect the two birds! Dave

    I am hoping to resurrect the two birds!

    Dave
  18. I was thinking the same thing. The other...

    I was thinking the same thing.

    The other possibility is that the 2716 EPROM you have purchased is too slow (the data is returned too late for the CPU to read correctly).

    Can you post a close-up...
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    Ah, you think the '

    Ah, you think the '<' is a '('. That makes more sense now...

    Agreed, Video RAM F8 first; followed by buffer E8 (74LS244) if that doesn't fix your problem.

    We need to isolate what is an artefact...
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    Let's sleep on it for tonight and see what words...

    Let's sleep on it for tonight and see what words of wisdom we get from dave_m for the morning...

    Dave
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    I am having difficulty in thinking that your...

    I am having difficulty in thinking that your problems are to do with anything other than the video RAM.

    Thoughts from anyone else?

    Dave
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    >>> And also, how a faulty video ram can cause...

    >>> And also, how a faulty video ram can cause the freeze in the execution?

    The test program is not freezing, it is constantly testing the VIDEO RAM and video circuitry until such time as it gets...
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    That looks OK to me - the PETTESTER is running...

    That looks OK to me - the PETTESTER is running OK.

    I suspect, therefore, you have a VIDEO RAM or video RAM circuitry fault somewhere.

    You ned to check the screen characters very carefully for...
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    Excellent, so you are getting there. The first...

    Excellent, so you are getting there.

    The first test is to checkout the VIDEO RAM. If the PETTEST ROM ‘jams’ at this screen there are two possibilities:

    1. The CPU has stopped executing...
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    So when you say 'nothing changed' can you refresh...

    So when you say 'nothing changed' can you refresh my memory about what you mean please.

    What is on the screen (if anything). Is the screen blank. Does it have the random characters.

    You can...
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