Apple IIc+ boot disk for DOS3.3 - test-drb@ccmp.vtda.org

6 Aug 2000

...
  > There are, of course, many other features in the
ROM; it's just a matter of
...
  > digging up the programming info.  And (since you
have such a late member of
...
  > the ][ series) there are also features in the
hardware, such as double-
 > resolution text, low-res, and high-res modes, that the ROM was never updated
...
   to handle.
 How do you get at these modes? Are they in the IIgs, also?

 Speaking of which, can you drive the IIgs graphics chip and sound chip,
 whatever they're called, from Applesoft? 
The double-resolution text mode is 80-column mode, and can be turned on
with PR#3.  This mode is supported by the ROM.

The double low-res (twice as wide, not half as wide!) and double hi-res
modes are not supported by the ROM.  You can write BASIC routines to use
them, but it is much faster to use assembly language routines called by
BASIC.  These modes are also in the Apple IIe and IIc.

The IIgs has super-res modes with hardware color fill available.  I am not
a IIgs programmer (I use mine as a IIe) but there may be ROM routines in
the toolbox to support those modes.  The same may be true for the IIgs
sound chip.  I have seen a BASIC program that used the sound chip, but all
it did was POKE the data into memory.

No Apple II has real support for even the built-in speaker in the ROM,
except for the Programmer's Aid #1 option for Integer BASIC which had tone
routines.

Paul R. Santa-Maria
Ann Arbor, Michigan  USA
paulrsm(a)ameritech.net