a604n fault trace

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Don't Panic. Please wash hands.

    Hi Jens, I messaged you a short while back on twitter about a schematic for the a604n and you said it was closed source, which I understand completely.

    I wonder if there is some redacted information you can offer. Really I just want to continuity check the pins of the ECS socket to each destination to eliminate, or repair bad solder connection. Of course the bottom side traces are easily visible, but not the hidden or topside traces. If there's any info you can offer I would be grateful. You can DM me in twitter if you'd like to keep any info private. Thanks jim (fuzzweed)

    Some A604n units have a connection between Denise-socket pin#35 (originally a 7MHz signal on the A500), and A600-trapdoor pin#67 (mostly labelled 14MHz in all the A600 schematics I have). This connection needs to be OPEN, which is why the units we've been delivering for years have a cut trace there.


    The reason is that many A600s have an Agnus chip installed that has a VBB designation, so pin#67 of the A600 trapdoor connector carries a negative voltage. This does not damage anything, but that voltage would be clamped by Indivisino ECS V2/V3, and the computer does not start (or start with garbled graphics).


    All the rest of the Denise socket is connected to the most logical pins on the A600 trapdoor connector.


    Like I wrote on Twitter/X, this memory expansion has been copied down to the last mechanical detail (minus the riser board - probably too complicated for the guy), and it appears to work for some customers. I don't care if people copy my work that way - after all, it's a clear sign that I've done a good job in designing this, and there's nothing to improve. The one thing I'm p*ssed about is that they don't give credit, and that support cases end up in this forum, so I have the work, and someone else makes the money.


    Jens

    I did understand correct, and your question was already answered.


    The marked pins are colour output pins from the ECS flicker fixer (or Denise), and they are not used on the A604n. Indivision ECS will detect that it's mounted on an A600 and go into "Denise shadow mode" where it sniffs the chip bus for data that is sent to Denise. The picture will be replicated in the flickerfixer, then written to the frame buffer and output at higher frame rate, just like all flicker fixers do.


    The special thing about this is that you don't even have any direct picture data on the trapdoor bus. You only have the chipset bus, but that's enough to replicate the picture that Denise outputs. Once you've understood the concept, you should understand that the colour output pins on the Denise socket are not used for anything in this configuration.


    Jens