# Apple IIe

The Apple IIe is a computer with many nice features, very good
expandability and a rather straightforward design, along with a
very complete documentation.

As it is now, Collapse OS is built upon ProDOS and doesn't
directly run the hardware. Maybe some day direct drivers will be
written, but the challenge is significant because the floppy
controller on the Apple IIe, unlike in many other machines, is
very bare. Sector/track detection has to be done entirely in
software with precise timing. Maybe one day...

# Reference documents

* Apple IIe Reference Manual
* Applesoft BASIC Programming Reference Manual
* Apple II BASIC Programming with ProDOS
* Beneath Apple DOS
* Beneath Apple ProDOS

# Installing Collapse OS

I didn't have the luck of having a RS-232 card on the machine I
acquired. I could have gone through some hacks (maybe the
joystick port?) which would have required the design of some
hardware adapter. Another possible route would be to craft a
floppy from another machine which could be read from the Apple
IIe, but floppy-related tools in Collapse OS are not mature
enough yet.

Since I haven't done so yet in any of the recipes, let's go with
the long, hard route: typing the whole thing in.

For this recipe, you need:

* An Apple IIe
* A floppy disk drive and some floppies
* A ProDOS disk (mine is ProDOS 8)

# The Monitor

We'll be typing in our stuff from Apple's Monitor program which
is documented in "Apple IIe Reference Manual". A cheatsheet is
available in monitor.txt.

Things can go wrong and you can lose your work. You are advised
to quickly become accustomed to ProDOS BASIC's BSAVE and BLOAD
commands to incrementally save your work to floppies.

# Typing it in

When you run "make" in /arch/6502/appleiie, in addition to
producing os.bin, it also spits the binary contents to the
screen in lines of 16 bytes and, at the end of each line, a
numerical checksum.

The idea is that with the help of these checksums, if you made a
typing error, you'll quickly locate it. The checksum is a simple
sum rather than a CRC16 because Applesoft BASIC doesn't support
fancy stuff like XOR.

After having typed a few lines (and saved them!), you can type
yourself a checksum checker in BASIC:

10 A=8192
20 N=0
30 FOR I=A TO A+15
40 N=N+PEEK(A)
50 NEXT I
60 PRINT N
70 INPUT X
80 A=A+16
90 GOTO 20

The result of "INPUT X" is ignored, but the pause give you the
opportunity to break the loop with Control+C.

You're ready for the real thing. The idea is to type it at its
home address, $2000. You'll do so in the Monitor (CALL -151).

Regularly, you'll want to come back to BASIC and save your work
with something like "BSAVE COS,A$2000,L$XXXX" with XXXX
being the length of the binary you've typed so far. Then, you
run "RUN" to do your checksum. Compare numbers you get from
BASIC with numbers you got from xcomp.fs. They're supposed to
match. The last line doesn't have a checksum, just be extra
careful with it.

Once you're ready, you can run the binary with "2000G" in the
Monitor.

# Alternative to typing: SPI hack through game port

See spihack.txt

# Creating a ProDOS boot disk

With ProDOS, it's easy to create a disk that will directly boot
to Collapse OS. To do so, begin with a bootable copy of your
ProDOS disk and remove everything from it except the "PRODOS"
file.

Then, copy your COS "BIN" file in there and make it into a SYS
file. That last part is a bit awkward. Given a BIN file named
COS, here's the BASIC commands to copy it to a SYS file:

] CREATE COS.SYSTEM,TSYS
] BLOAD COS,A$2000,L$2000
] BSAVE COS.SYSTEM,A$2000,L$2000,TSYS

If COS.SYSTEM is the only SYS file besides PRODOS, then it the
disk will boot directly to Collapse OS.