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IIgs peculiarities

Just got interested in the IIgs and checked some documents about it.
But the following questions remain unanswered (or I just missed
something somewhere):

1) IIgs ROM 03 has additional bit in the shadowing register (and the
default 'enable') to include Text Page 2 ($800..$BFF), but the
firmware keeps it disabled for some reason. And the "Alternate Display
Mode" option is still available in the Control Panel.
Where is the logic to this? Just leaving the register to shadow Text
Page 2 is the way to go, and no "Alternate Display Mode" is needed at
all.

2) I tried manually setting "Slow" speed by changing the high-bit of
the appropriate register (through Monitor), but nothing happens. And
the content of the register doesn't change. Is there IRQ subroutine
keeping overwriting it? Or is there a special way to access it?

3) IIgs maximum RAM - banks $00 .. $7F are specified as RAM range.
This makes exactly 8MB. But the manuals keep saying 8.25MB. What is
the truth and where those 256KB came from?

4) Memory expansion - according to what I've seen the connector
provides for 2^10 rows/columns and 4 banks (CROW1/CROW0). This makes
4MB. How to go beyond this up-to 8MB? Is the signal "MSIZE"
responsible and how?

5) The memory expansion board may contain ROM, banks $F0+. Does the
FPI know the installed ROM on the motherboard and redirect the other
memory range to the expansion? Is pin #57 of FPI configuring this or
FPI chips on ROM 03 are newer?

6) If a ROM disk is to be present in banks $F0 .. $FB, what the format
should be? Just a ProDOS image which then shows with it's volume name?

TIA,
  -- Vlad