80 Column is used without Aux Card Installed

["Bryan Parkoff" <nospam@nospam.com>]

Hello,

    I have an experiment to do with Apple //e.  80 column card is not 
installed in aux slot.  I typed, "C00D:00" in the monitor prompt to turn on 
80 column.  It is now in 80 column.  You may notice that each character in 
odd position is duplicated in even position.
    Do you know why?  I may explain why.  During CAS' clock cycle falls, 
data is read from main RAM while it is floating on the data bus during Phase 
1.  Then floating data on data bus is still valid when Phase 0 rises before 
floating data is driven to the video generator.
    I can't tell if floating data bus is valid, but I do know that during 
Phase 0 and Phase 1 floating data for even/odd position is sharing the one 
74LS374 chip (video latch).
    If 80 column aux card is installed, 74LS245 chip is available to prevent 
floating data being overwritten between main data and aux data on one 
databus.  Then two 74LS374 chips are used.
    What do you think the fact if I am correct or wrong?  Hint: LDPS' is 
running at 14MHz while 7MHz is turned off.  I have no idea how LDPS' read 
twice from shared 74LS374 chip.

Bryan Parkoff