1.4) What is the Atari 1200XL?

Introduced in December 1982 and shipped in March 1983, the Atari 1200XL was
intended to eventually replace the Atari 800 while maintaining compatibility
with the earlier model.

Innovations relative to the 400/800 include a full 64KiB of RAM and a
significantly revised XL Operating System (ROM expanded from 10KiB to 14KiB).

The 1200XL is the only 8-bit Atari computer to feature two LED indicator
lights (L1, L2).  Normally they are both <OFF>.  L1 <ON> means the keyboard is
disabled.  L2 <ON> means the new International Character Set is selected.

Keyboard enhancements introduced with the 1200XL include the new [HELP] key as
well as four programmable functions keys ([F1], [F2], [F3], [F4]).  Console
Speaker sounds (keyclicks and system beeps) output through the built-in
speaker on the 400/800 are heard from the television or monitor speaker on the
1200XL.  The toggle action of the [CAPS] key was altered compared to the
400/800.  The key auto-repeat rate is user-alterable.  The [RESET] key is
directly wired to the SALLY 6502 reset line.

  1200XL Function key effects, redefinable:
     [F1] Cursor up          [SHIFT]+[F1] Cursor to upper-left corner (home)
     [F2] Cursor down        [SHIFT]+[F2] Cursor to lower-left corner
     [F3] Cursor left        [SHIFT]+[F3] Cursor to start of physical line
     [F4] Cursor right       [SHIFT]+[F4] Cursor to end of physical line

  1200XL Function key effects, non-redefinable:
     [CONTROL]+[F1] Keyboard enable/disable (console keys unaffected)
     [CONTROL]+[F2] Screen DMA (ANTIC) enable/disable
     [CONTROL]+[F3] Key click sound enable/disable
     [CONTROL]+[F4] Domestic/International character set toggle

Additional 1200XL Operating System enhancements compared to the 400/800 OS:
- Self Test program
- Text screen fine scrolling is available
- The Resident Diskette Handler can read/write disk sectors having variable
   length from 1 to 65536 bytes.
   Default = 128 bytes (matching the 400/800 static value)
- The Resident Diskette Handler can write a sector to the disk without a
   read-verify operation always following it.
- Universal OS for both NTSC and PAL systems (including independent values
   for cassette timings and for keyboard auto-repeat functions)

A few features from the 400/800 are lacking in the 1200XL.  Most prominently,
the 1200XL has only 2 controller ports, and no Memo Pad / Blackboard mode.

With the 1200XL Atari made an apparent decision to preclude peripherals from
drawing their power from the computer via the SIO bus:
- The 1200XL lacks +12V on SIO pin 12, as was available on the 400/800.
- On the 1200XL the +5V/Ready line (pin 10) on the SIO port supplies enough
   current for the Ready ("Computer On") function but not enough current for
   peripherals designed to use the line as their power source.
   ("FIX": Replace 100 Ohm resistor R63 with a 0 Ohm to 1 Ohm resistor, or a
   jumper wire.)

The labels on several of the 1200XL keyboard keys differ slightly from those
of the 400/800:     400/800                1200XL
                    [CTRL]             --> [CONTROL]
                    [SYSTEM RESET]     --> [RESET]
                    [CAPS LOWR]        --> [CAPS]
                    [DELETE BACK S]    --> [DELETE BACK SPACE]
                    "Atari logo" key   --> "Inverse video" key

System initialization types supported:
- "ATARI" rainbow logo/graphics demo screen: Turn on computer with no
   cartridge inserted and no powered disk drive #1.
     - Press [HELP] from the "ATARI" logo screen to access Self Test program.
- Cartridge: Turn on computer with cartridge inserted.
- Cassette boot: (boot cassette may or may not require cartridge inserted)
    1. Hold down [START] while turning on the computer. (system buzzer sounds)
    2. Press [PLAY] on the program recorder with boot cassette inserted.
    3. Press [RETURN] on the computer.
- Disk boot: (boot disk may or may not require cartridge inserted)
    Turn on computer with boot disk inserted in powered disk drive #1.

Box: "A Step Into the Future"

Single version of the Atari 1200XL:
  o  Domestic version for NTSC M television (North America)
     - 6502 MPU (Atari SALLY), C014806
     - ANTIC NTSC version, C012296
     - GTIA NTSC version, C014805
     - 14KiB Operating System ROM, C060616 + C060617
        - Floating Point Package (FPP) included, identical to the 400/800 FPP
        - Most units: XL OS Rev.A
        - Rare units: XL OS Rev.B
     - Monitor port is Atari 5-pin
        - Lacks the chrominance video signal on pin 5
     - Switch Box jack for RF output for TV
     - Channel switch on back of computer selects TV output RF channel: 2 or 3
     - TV Switch Box and TV connecting cable both supplied with computer

Power: Used with an external 9 volt AC transformer power supply, input power
31 VA; shipped with Atari CA017964.

- The Atari 1200XL Home Computer Owner's Guide C061418
- Atari 1200XL Home Computer Field Service Manual FD100217

1200XL visual tour:

Scott Stilphen mentioned this 1200XL easter egg on 10 Feb 2006:
   On 1200XLs, if you select 'all tests', when it gets to the keyboard test
   it'll type out the programmer's name.

The 1200XL was manufactured at Atari's plant at 1215 Borregas, Sunnyvale CA
from January 1983 to May 1983, and was also made by Atari Taiwan Manufacturing
Corp. from April 1983 to July 1983.  Serial numbers:
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