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33904Re: [midatlanticretro] 6502 mystery motherboard on Ebay - what is this?

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  • joshbensadon
    Jan 4, 2014

      ---In midatlanticretro@yahoogroups.com, <ragooman@...> wrote:

               oh yea, 
      But there's also no telltales signs of any mass storage , eg, cassette ports, floppy ports
      There's a 100mil header on the bottom left side, usually meant for a keyboard cable
      Also appears to be a Char Generator IC in column N at the top right -  but that would be needed regardless.
      But I don't see any connector where the CRT would be cabled, maybe it's shared with that same 100mil header.
      One thing that looks interesting is there are 2 separate Xtals right beside the 6502.
      As if it has the option to select a diff speed  - not sure unless we can clearly see all of the actual part# on there.
      But that could've be done using just a clock divider
      Would be nice to see a hi-res photo for this instead of that blurry pic

      Hi Dan,  Good point about the lack of mass storage.  I would guess the 100mil connector would be used for power, there's a few filter caps right there.  Lots of pins, so video can come out too.  Video is also available on some test pins right above the EPROM, There's Video,Horizontal and Vertical.  A monitor could tie into those points.  Interesting is the 50Hz signal in the row above that.  Could this be a European model?  But where's the keyboard connector? Under the board perhaps? Or perhaps the open socket at E7?  My guess about the two crystals.  One is used to get the right video speed, the other is used for the right baud rates.  The CPU would likely use a divided tap off the video clock to simplify the sharing of RAM etc.  The UART and CPU can always synchronize through the use of UART status flags.
      Finally, I think you are right about the char generator being that chip at N7 (top right).

      I think it's more fun that it's a fuzzy picture!  I hope Bill wins it and uploads a high res picture.

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