Re: Varied IIgs Q's

[nathan@visi.com (Nathan Mates)]

In article <338778f3.13043758@167.152.149.11>,
Edhel Iaur, Esq. <LOSETHECAPITALWORDSedhel@bigfoot.com> wrote:
>When I format a 3.5" disk for ProDOS in System 6.0.1, one of the
>options is 2:1 or 4:1.  What's this do?  Interleave?  If so, why would
>anyone mess with it?

   Yes, interleave. Unidisks' optimal speed is 4:1, Apple 3.5" drives
is 2:1. If you're only using one type of drive, use the speed for
that. If you're using both types, it's best to go with 4:1, as that'll
be slightly slower on Apple 3.5" drives. [2:1 on Unidisks causes it to
blow a full revolution every time it tries to read sequential sectors,
a big timesink]

>Is there an NDA that lets me view the files that Teach does?  Where is
>it?

   Try ShadowwWrite (which was later renamed Hermes I think). Look in
the usual places for software. Just found it at apple2.caltech.edu,
pub/apple2/addons/nda/shdwwrite133.shk

>My IIgs came with an AE GS-RAM+.  My ads in old _A+_ magazines say it
>was supposed to come with software.  Is there a way for me to get it
>now?

   Mine came with a disk with a memory checker. That's about it.

>What is ProDOS 16?  Is it running beneath GS/OS or something?  Is it
>backwards compatible with ProDOS 8 programs?

   When Apple released the GS, they really didn't have a good OS ready
for it, so they wrapped a 16-bit interface around ProDOS and called
that ProDOS 16. [And ProDOS became ProDOS 8 just to differentiate it].
ProDOS 8 programs don't run under ProDOS 16 or GS/OS. When Apple
finally released a good OS for the GS, that was GS/OS. GS/OS is
backwards compatible to ProDOS 16 calls and file formats, but GS/OS
adds a lot above and beyond ProDOS 16. Calling conventions and disk
file formats for executables changed in GS/OS, so a lot of newer stuff
will just not run under ProDOS 16.

   ProDOS 16 was useful mainly for taking up less disk space than
GS/OS, which is why a number of 16 bit titles used it. 

>What the heck is up with the 640 mode?  Is it normal, real, 640 x 200?
>How many colors are there really?  I thought there were only 4 per
>line, but I've seen 15 colors per line in the 640 mode.  Is this some
>really funky deal like standard & double high-res?  I zoom in on a
>blue area in the 640 mode, and I see a magenta and white dither.

   In the 32K block of memory, there are 200 scanlines, and 160 bytes
per line, giving 2 bits per pixel. Each palette still is 32 bytes wide
at 2 bytes per entry (0RGB 4bpg format), while you can place 4 8-byte
palettes in that space. The GS's hardware does some dithering tricks
to make these 4 sub-palettes appear like more colors, but as they're
dithered, you can't edit one color without affecting others. (This is
why the default 640x200 palette has 2 grays, and interesting patterns
if you put some colors next to each other) By setting all 4
sub-palettes to the same values, you can get 4 pure colors per pixel.

   Your magnification program is probably expanding stuff one pixel (2
bits) at a time, while ignoring the quirks from putting stuff in
certain bit positions as well as the other color in the same nibble (4
bits). 

>How can I associate various filetypes to various programs, so I can
>double-click th edocs in Finder, and have the right program open?

   Easiest way: get an Icon Editor (IconED 1.3 or 2.0, or DICeD --
IconED 2.0 is in the apple2/utils folder at Caltech) and make up a
custom item with the application path set to whatever program you want
to associate them with. Place this icons file on one of your disks,
and it should work. [There's the possibility of sort order problems,
so you might want to try putting your file either first or last in the
directory]

>How many disk drives can you hook up to a IIgs, and where do they get
>mapped to (slot/drive)?

   Off the disk port, up to 2 5.25" drives, and 2 3.5" (unidisks or
Apple 3.5"s). More than that, and you'll probably blow the normal
power supply. 5.25"s are mapped to S6D[12]; 3.5s go to S5D[12] first,
then spill over to slot S3D2 (S3D1 sorta reserved for ProDOS's builtin
/RAM disk using the second 64K of memory). If you've got /RAM5 active,
it's usually in S5D2 unless you're booting from it, when it drops to
S5D1.

   HDs and the like tend to spill over as much as possible elsewhere
(RamFAST's control panel lets you select what drives go where) under
ProDOS 8; under GS/OS, they're all available. GS/OS doesn't need
"slots" and "drives" anymore; they're simply given a drive "number"
and keeps around which drive # of which device driver is in charge of
it. Much more logical and expandable; too bad they didn't do that
earlier on Apple IIs. [I think the Apple III's OS had some nice stuff
like that, but I could be mistaken.]

Nathan Mates
--
<*> Nathan Mates http://www.visi.com/~nathan/      <*>
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