1.1) What is an Atari 8-bit computer?

Subject: 1.1) What is an Atari 8-bit computer?

Based in Silicon Valley in the U.S.A., the company known as Atari produced
a line of home computers from 1979 to 1992 often referred to collectively as
the "Atari 8-bits," the "8-bit Ataris," the "400/800/XL/XE series," etc.

The computers included the 400, 800, 1200XL, 600XL, 800XL, 65XE, 130XE, 800XE,
and the XE Game System.

These machines competed in the marketplace most directly with the likes of the
Commodore 64 series, the Apple II series, the Texas Instruments TI99/4A, and
the Radio Shack Color Computer, among others. Of these, the 8-bit Atari is
most similar to the Commodore 64.

In marketing their computers to the public, Atari always had to contend with
their company history and reputation as a maker of video games. While the
8-bit Atari computers in their heyday were technically quite comparable if not
superior in the worlds of home and business personal computing, they also live
up to the name "Atari" with a huge library of video games which were often
outstanding for their time.

The 8-bit Atari computers do not use the same cartridges or floppy disks as
any other Atari platforms, such as the 2600 Video Computer System (VCS), the
5200 SuperSystem, the 7800 ProSystem, or the ST/TT/Falcon computers. All of
these but the 5200, however, do share the same joystick/controller hardware
port.

The 5200 SuperSystem is actually nearly identical to the 8-bit computers
internally, yet cartridges for the 5200 and the 8-bit computers cannot be
exchanged, primarly due to the physically different cartridge ports.

Here are some of the performance specifications of the 8-bit Atari computers:

(Some of the rest of this section by Bill Kendrick)

CPU: 6502 (MOS Technology)

CPU CLOCK SPEED:
NTSC machines: 1.7897725 MHz
non-NTSC machines: 1.773447 MHz

SCREEN REFRESH RATE:
59.94 times per second (Hz) on NTSC Ataris
49.86 Hz on PAL machines

GRAPHICS MODES:
ANTIC CIO/BASIC Display Resolution Number of
Mode # Graphics # Type (full screen) Colors
---------------------------------------------------------------
2 0 Char 40 x 24 1 *
3 - Char 40 x 19 1 *
4 12 ++ Char 40 x 24 5
5 13 ++ Char 40 x 12 5
6 1 Char 20 x 24 5
7 2 Char 20 x 12 5
8 3 Map 40 x 24 4
9 4 Map 80 x 48 2
A 5 Map 80 x 48 4
B 6 Map 160 x 96 2
C 14 ++ Map 160 x 192 2
D 7 Map 160 x 96 4
E 15 ++ Map 160 x 192 4
F 8 Map 320 x 192 1 *
F 9 + Map 80 x 192 1 **
F 10 + Map 80 x 192 9
F 11 + Map 80 x 192 16 ***
* 1 Hue; 2 Luminances
** 1 Hue; 16 Luminances
*** 16 Hues; 1 Luminance
+ require the GTIA chip. 1979-1981 400/800's shipped with CTIA
++ Not available via the BASIC GRAPHICS command in 400/800's.

GRAPHICS INDIRECTION (COLOR REGISTERS AND CHARACTER SETS):
Nine color registers are available. Each color register holds any of 16
luminances x 16 hues = 256 colors. (Four registers are for player-missile
graphics.

Character sets of 128 8x8 characters, each with a normal and an inverse
video incarnation, are totally redefinable.

PLAYER-MISSILE GRAPHICS: (byte height and OR corrections from Piotr Fusik)
Four 8-bit wide, 120 or 240 byte high single color players, and four
2-bit wide, 120 or 240 byte high single color missiles are available.
A mode to combine the 4 missiles into a 5th 8-bit wide player is also
available, as is a mode to OR colors or blacken out colors when players
overlap (good for making three colors out of two players!) Players
and missiles have adjustable priority and collision detection.

DISPLAY LIST INTERRUPTS (DLI's):
Screen modes can be mixed (by lines) down the screen using the Display
List - a program which is executed by the ANTIC graphics chip every
screen refresh:

All other screen attributes (color, player/missile horizontal position,
screen width, player/missile/playfield priority, etc.) can be ajusted
at any point down the screen via DLI's.

SCROLLING:
Fine scrolling (both vertical and horizontal) can be enabled on any
line on the screen.

SOUND:
Four voices of 8-bit pitch-resolution, 4-bit volume-resolution,
8-distortion sound can be produced. 2 voices (1 and 2, and/or 3 and 4)
can be combined to make 16-bit pitch-resolution. Also 4-bit volume-only
modes can be enabled for digitally sampled sound replay.

A fifth "voice" is produced by the internal speaker on Atari 400/800's
(for keyclick and buzzer) and in the XL's and XE's this was
(fortunately!) rerouted through the normal audio output, and the
keyclick can be disabled.