Racing the Beam : the Atari Video Computer System - Index of

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2.3 The smallest vertical unit in the VCS graphics system is a single scan line. The smallest unit of horizontal space is a color clock. The detailed view of Pitfall Harry’s head and neck on the left clearly shows that the “pixel” defi ned by these is rectangular, not square. This shape became a design feature; for example, the rectangular blocks help Pitfall Harry’s legs appear longer than they would with square pixels. The Combat biplane sprite on the right appears to be comprised of square pixels because that program uses a two-line kernel, which updates the sprite graphics only every two scan lines. background color so that a part of the scan line is drawn fi rst in one color and then in another involves storing a new value in the TIA register that holds the screen background color. A store requires three of the 6502’s processor cycles to complete. (Practically, more computation has to be done to get the new color value ready. This might involve loading an eightbit number or performing some mathematical operation that yields a new value.) Because each machine cycle corresponds to three color clock cycles, and because the instruction to store a new value in the appropriate TIA register is essential in every case, a strip of background color cannot be less than 3 processor cycles × 3 color clocks per processor cycle = 9 color clocks wide—just a bit more than the width of a sprite. Figure 2.4 depicts a typical VCS frame, this one from Pitfall!, including both the visible parts of the picture and those during which the electron beam repositions itself. The fi rst three lines are called “vertical sync.” During this time, the VCS signals to the television that a new frame needs to start. The television responds by beginning to reposition the electron gun. Next comes the “vertical blank” period, which, as mentioned earlier, represents the time it takes for the television to actually reposition the beam for the next frame. This takes as long as it does to draw 37 scan lines. During this time, the VCS program can handle game inputs and run any logic needed to set up the new frame of image and sound. Next comes the main television picture. Each scan line of television picture is composed of a horizontal blanking period of 68 color counts, or 2 Combat [29]
2.4 The Atari VCS television image is broken down and key regions and measures are indicated. This television protocol image is based on the one in Wright, Stella Programmer’s Guide. a little more than 22 machine cycles, and a visible picture period of 160 color counts, or a little more than 53 machine cycles. The numbers at the top show the clock counts and those at the bottom show the machine cycles. The short horizontal blank period is used to set up the next line of the display, for example, changing sprite and playfi eld graphics. If the programmer needs to make a change mid-scan line—for example, changing playfi eld graphics for an asymmetrical playfi eld—it is necessary to cycle count to insure the TIA registers change at exactly the right position in the scan line. The relative size of both a color clock and a scan line are marked in relation to the screen in fi gure 2.4. Next comes the overscan period. At the time the Atari VCS was designed, the position of the CRT in the television casing varied considerably. The overscan period is a “safe zone” to account for this, and it provides the programmer with another thirty scan lines of time to run program logic. [30]
Page 2 and 3: Racing the Beam
Page 4 and 5: Nick Montfort and Ian Bogost The MI
Page 6: Contents Series Foreword vii Acknow
Page 9 and 10: • an awareness of and discussion
Page 11 and 12: A shout-out goes to the bloggers an
Page 13 and 14: 1982 Atari 5200 introduced; Atari V
Page 15 and 16: eception and operation of computer
Page 17 and 18: specifi c machines can reveal the r
Page 19 and 20: important contributions as well. Ce
Page 21 and 22: game encourages continued play and
Page 23 and 24: 1.1 To play Atari’s Home Pong, th
Page 25 and 26: Design of the Atari VCS The enginee
Page 27 and 28: RAM, the memory programs use to sto
Page 29 and 30: of the basic hardware capabilities
Page 32 and 33: Combat 2 The Atari VCS console was
Page 34 and 35: ROM technologies that are not truly
Page 36 and 37: and the available VCS controllers.
Page 38 and 39: allows for bits 4 (left player, up)
Page 40 and 41: Where VCS Meets TV The processor is
Page 44 and 45: For Two Players Combat imitated the
Page 46 and 47: VCS programs. Even when the machine
Page 48 and 49: Game Variations The game’s variat
Page 50 and 51: .BYTE $24 ;Game 1: 0010 0100 TANK .
Page 52 and 53: Storing a large set of instructions
Page 54 and 55: two human players, as it had no AI.
Page 56 and 57: Adventure 3 What video game could b
Page 58 and 59: computer platforms of the early 198
Page 60 and 61: PF0 PF1 PF2 bits: bits: bits: 4 5 6
Page 62 and 63: merely press the joystick in a comp
Page 64 and 65: of Tank had been developed jointly
Page 66 and 67: Turning a missile on for the entire
Page 68 and 69: 3.2 If Adventure had used bounding
Page 70 and 71: 3.3 This map of the world in Advent
Page 72 and 73: why the cursor matches the walls an
Page 74 and 75: Today, there are perhaps a handful
Page 76: different perspective to let the pl
Page 79 and 80: Pac-Man did fairly well in Japan, b
Page 81 and 82: More important than the sheer amoun
Page 83 and 84: equirements of the TIA playfi eld,
Page 85 and 86: 4K ROM provides greater fl exibilit
Page 87 and 88: Pac-Man would have been unrecogniza
Page 89 and 90: a very unusual production run, give
Page 91 and 92: 4.3 The VCS Ms. Pac-Man has bonus f
Page 94 and 95:
Yars’ Revenge 5 In 1981 Yars’ R
Page 96 and 97:
power, graphics, and controller set
Page 98 and 99:
Asteroids, on the other hand, makes
Page 100 and 101:
some cases, as important as the ses
Page 102 and 103:
up and down are both laid out in RO
Page 104 and 105:
There are reasons for these intrica
Page 106 and 107:
The Code Zone Yars’ Revenge featu
Page 108 and 109:
Color port of Yars’ Revenge in 19
Page 110:
mechanic), and up from the bottom (
Page 113 and 114:
[100] our contribution to the compa
Page 115 and 116:
hundred people. These teams are div
Page 117 and 118:
Design Center. The company later ad
Page 119 and 120:
(COLUP0/COLUP1) and graphics (GRP0/
Page 121 and 122:
comprises Combat’s planes, Slot R
Page 123 and 124:
that this idea would make an intere
Page 125 and 126:
As stated here, the high bit of the
Page 127 and 128:
contemplated all at once. It offers
Page 129 and 130:
Another graphical detail can be see
Page 132 and 133:
Star Wars: The Empire Strikes Back
Page 134 and 135:
tribution through Sears, the compan
Page 136 and 137:
In U.S. toy industry reports and tr
Page 138 and 139:
ships, and many other sorts of lucr
Page 140 and 141:
movie are fairly clearly represente
Page 142 and 143:
“original” concept needed to be
Page 144 and 145:
andom in one of a few locations on
Page 146 and 147:
VCS, including Bachelor Party, Beat
Page 148:
Things could have come about very d
Page 151 and 152:
like the NES, which had two action
Page 153 and 154:
enjoyed so little success in the ma
Page 155 and 156:
endering requirements, the sprite-m
Page 158 and 159:
Afterword on Platform Studies As cr
Page 160 and 161:
een applied to digital media as wel
Page 162 and 163:
tational platforms, such as Ben Fry
Page 164 and 165:
Notes We discuss the technologies u
Page 166 and 167:
25. The discussion that followed th
Page 168 and 169:
9. Alexander, “Video Games Go Cru
Page 170 and 171:
21. Activision’s method is clearl
Page 172 and 173:
Bibliography Texts Aarseth, Espen.
Page 174 and 175:
Herman, Leonard, Jer Horwitz, Steve
Page 176 and 177:
Williams, Geoff. “10 Businesses F
Page 178 and 179:
Higinbotham, William. Tennis for Tw
Page 180:
Coppola, Francis Ford. The Godfathe
Page 183 and 184:
Alcorn, Al, 7 Amidar (VCS game), 12
Page 185 and 186:
Combat (cont.) handicapping adjustm
Page 187 and 188:
Journey Escape, 124 Joysticks, 22-2
Page 189 and 190:
Pixels, 28, 29 Platforms, 16, 23, 4
Page 191 and 192:
Sports-themed games, 65 Sprite grap
Page 193:
Yars’ Revenge (VCS game), 81-97 a
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