>What if it's only for a few bytes (<10) at powerup?
>
The power drain only occurs in the cycles when both roms are active at the
same time.
>"by a lot" - how much?
>
About 20% to 50% shorter life if this is sustained.
>Again, what if for only a few bytes?
>
If this drain is only occuring for about 20 cycles on power up and nothing
more, the drain is not worth worrying about.
>Is there anything that can be added to help the situation?
Don't enable two roms at the same time. Either isolate the second rom and
add extra decoding logic to disable it when you new rom is to override. This
is how the GameShark and other like products work to "Patch" video games.
>
>"most cases" - Other than building something, is there
>any way to be sure?
>
When you are dealing with driving the bus with two buffers, a no no, bad
things happen and things can get unpredictable.
>I assume this isn't "wired-and" since ROMs aren't open collector?
>
It's an AND since ground tends to override an output driving the line high.
>And I assume pull-up resistors aren't necessary for logical "AND"?
No, pull up are only used for open collector outputs since the output is
either shorting the line to ground to an open circuit, the pull up resistor
will then drive the line high via the connection to 5 volts. So if two open
collector lines are tied together, either one can drive the circuit to
ground and therefore generate a logical AND.
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