Re: Apple II GS Questions

[supertimer@aol.com (Supertimer)]

Jeff Lemke <lemke@terra.cira.colostate.edu> wrote:

>Brian Hammack wrote:
>> 
>>  Bob chanted almost zenlike back at me:
>> 
>>     |  I also have a Lazer 128, Apple compatible I got from Sears in
>>     | 1989.  How would this compare to the GS?
>> 
>> It compares to a //c.  The GS does 4096 colors, 11 voices, 8 megs RAM,
>> runs 16-bit forked files, slices, dices, julliens, and plain rocks.
>> 
>
>
>The IIgs may have a palatte of 4096 colors to choose from, but it cannot
>display more than 16 of those colors at a time at most, if I remember
>right, and displays even fewer colors at higher resolutions.  Not enough
>video RAM, I guess.

No, no, no.  That's 16 colors PER PALETTE out of a range of
4096.  However, the IIGS has enough video memory for
16 palettes.  Thus, it is really more of a 256 color machine.
Any one of the 16 palettes can be assigned to any scan line.
That means any particular horizontal line is restricted to a
particular 16 color palette, but the entire screen can easily
have up to 256 colors at the same time.

The IIGS also as a 3200 color mode.  In this mode, the IIGS
can display up to 3200 colors at once.  A separate 16 color
palette can be assigned to each of the 200 scan lines.  How
to do this with only enough video memory for 16 palettes?
By using the CPU to swap palettes at precisely the right
moment.

As you can imagine, 3200 color mode is mostly used to
look at GIFs and other pictures, because it steals CPU
time.

256 color mode can be found in games such as DuelTris
because it does not eat up CPU time and that time can
be used for animation.

>That's a real graphic display crippler, but it can
>be cured with a rather expensive Second Sight board.  Also, it seems I
>heard from someone that there is some kind of a drawback or two to
>having more than 6 or 7 MB of RAM, but I don't remember what that is.

More than 5MB on a ROM 3 unit will result in the need
to disable DMA on the Apple High Speed SCSI card
and the older (pre-revision D) RamFAST unit.  The
revision D RamFAST unit can DMA easily with 8MB,
so that card will solve this problem.  Apple and
early RamFAST SCSI users just need to turn off DMA,
which slows down their hard drive access a little.  Later
RamFAST users do not need to do this and can run
their hard drives with full DMA speed.