Quote:
Originally Posted by SiriusHardware
On the prototypes (Mine, Tim's) the capacitors from A0-A7 to 0V were never fitted and fitting them could have unintended consequences. The ones from A8-A11 to 0V were necessary - 180pf-200pf in my case, to resolve the problem where software attempting to write to a location in any given memory page would sometimes write to the same location in a different memory page as well.
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My suspicion is that the capacitors on A8 to A11 were required due to the combined load effect of the inputs of the pic and the 74ls ttl address decoding on the mk14. An alternate to the buffers or capacitors might be to swap the 74ls address decoding for 74hct.
Then we might start getting into an argument about where to draw the line for retro hardware, though I think the pic already sets an era that would allow 74hct, but that is on a separate board rather than a mod to the mk14.
If Ian’s board doesn’t show memory corruption with the buffers we probably need to experiment with taking them out to confirm they are the fix and not just some other effect due to the board layout etc.