30 Mar
2006
30 Mar
'06
1:04 p.m.
There is also
another circuit board mounted underneath the one with
the EPROMs that contains lots of other chips: M74LS22P, M74LS08P x 2,
HD14002BP, M74LS00P, M74LS138P, M74LS02P, MC14013B, MC14011B.
Ouch! A lot more logic than I was expecting (I was hoping it was
just an
address decoder mapping the ROMs into one of the gaps in the HHC's
memory
map). This would appera to be some kind of paging circuit (you've
got a
couple of D-type flip-flops there that could be used to hold the
selected
bank number).