IIgs hardware inquiry - memory expansion slot

[derek@slab.slip.uiuc.edu (Derek Taubert)]

Just for the sake of argument...

/CDIR is only low while reads are being done in banks $02-$7F, and $F0-$FD.
That leaves a bunch of banks "unavailable" to the expansion slot.

Let's say that I have some DRAM (please, no refresh arguments here, just
assume that I've got that covered).  If I were to latch the bank address off
of the data lines on the rising phase 2 and determine that my bank was in the
range of $80-$DF, I could take the FRA0-9 inputs, the CROW0-1, and the latched
bank address and munge some sort of address/enable lines for this DRAM.

NOW...  Since /CDIR would be high, would it still be ok for me to place my data
on the data lines?  Ok, better question...  If I somehow managed to fill banks
$02-$7F with memory, would the memory manager in the IIgs bother looking beyond
$7F to see if there was anything in $80-$DF?  For that matter, how about the
space in $E2-$EF?

If so (I don't need an answer for this one), why isn't /CDIR low for all of
these unused banks?  I know that there is no shadowing going on in them, as
an empty ROM 1 will be full of data = bank address.

Happy hardware hacking,
Derek