List of 8-bit computer hardware graphics


This is a list of notable 8-bit computer color palettes, and graphics, which were primarily manufactured from 1975 to 1985. Although some of them use RGB palettes, more commonly they have 4, 16 or more color palettes that are not bit nor level combinations of RGB primaries, but fixed ROM/circuitry colors selected by the manufacturer. Due to mixed-bit architectures, the n-bit distinction is not always a strict categorization. Another common mistake is that some assume that a color palette of a given computer is what it can display all at once. Resolution is also a crucial aspect when criticizing an 8-bit computer, as many offer different modes with different amounts of colors on screen, and different resolutions, with the intent of trading off resolution for color, and vice versa.

Sample image Color test chart 3-bit, 8-color palette 6-bit, 64-color palette

World System Teletext

Level 1
See also: World System Teletext § Levels

World System Teletext Level 1 (1976) uses a 3-bit RGB, 8-color palette. Teletext has 40×25 characters per page of which the first row is reserved for a page header. Every character cell has a background color and a text color. These attributes along with others are set through control codes which each occupy one character position. Graphics characters consisting of 2×3 cells can used following a graphics color attribute. Up to a maximum of 72×69 blocky pixels can be used on a page.

0 1 2 3 4 5 6 7

Apple

Apple II series
See also: Apple II graphics

The Apple II series features a 16-color composite video palette, based on the YIQ color space used by the NTSC color TV system.[1][2] The Apple II features "lowres" and "hires" modes.

Number — nameYIQNumber — nameYIQ
0 — black*000 8 — brown***0.25−0.50
1 — magenta0.250.50.5 9 — orange*0.510
2 — dark blue0.25-0.50.5 10 — grey #2**0.500
3 — purple*0.50-1 11 — pink0.750.50.5
4 — dark green0.25-0.5−0.5 12 — green*0.50−1
5 — grey #1**0.500 13 — yellow0.7500.5
6 — medium blue*0.5-10 14 — aqua0.75-0.5−0.5
7 — light blue***0.75-0.50.5 15 — white*100
  • Note: Colors with italic text and marked with three asterisks (***) are out of the RGB gamut.

The Apple II features "lo-res" and "hi-res" modes. The 40x48 pixel lo-res mode allowed 15 different colors plus a duplicate gray(**).[3] *The majority of Apple graphic applications used the hi-res mode, which had 280×192 pixels (effectively 140x192 on a color monitor). The hi-res mode allowed six colors: black, white, blue, orange, green and purple.

High bitPixel pairNumber — NameYIQ
0000 — black000
0011 — purple0.511
0102 — green0.5−1−1
0113 — white100
1004 — black000
1015 — blue0.51−1
1106 — orange0.5−11
1117 — white100
Lo-res mode Hi-res mode

Atari

Atari 400/800/XL/XE

The early Atari 400 and 800 computers use a palette of 128 colors (a bit similar to the one used on the Atari 2600 console, and the Commodore 16 and Plus/4), using 4 bits for chrominance, and 3 for luminance. Screen modes may vary from 320×192 (384x240 with overscan) to 40×24, using 2 or 4 simultaneous colors, or 80×192 (96x240 with overscan) using 16 colors. After 2 years (late 1981) the CTIA graphics chip was replaced with the GTIA chip thus increasing the palette to 256 colors (CTIA and GTIA).

The ANTIC chip in the Atari 8-bit family computers (400, 800, XL and XE models) has an instruction set to run programs (called display list) which permits many more colors on the screen at once. There are a number of possible software-driven graphics modes.

Mattel Aquarius

The Mattel Aquarius computer has only a text mode with 40×24 characters, which graphic mode is obtained from low resolution blocks, providing an 80×72 resolution. The color attribute area is also on this 40×24 characters area, and used from a pixel group of 2×3. The colors used in the palette are fixed and 16.[4]

0 — black 1 — red 2 — green 3 — yellow 4 — blue 5 — magenta 6 — cyan 7 — white
8 — grey 9 — cyan_ 10 — magenta_ 11 — blue_ 12 — yellow_ 13 — green_ 14 — red_ 15 — black_

Commodore

For all the following computers of this brand, the U and V coordinates for the composite video colors are always the cosine and the sine, respectively, of angles multiple of 22.5 degrees (i.e. a quarter of 90°), as the engineers were inspired by the NTSC color wheel, a radial way to figure out the U and V coordinates of points equidistant from the center of the chroma plane, the gray. Consumers in Europe (which uses PAL) considered the Commodore colors to be more "washed out" and less vivid than those provided by computers such as the ZX Spectrum.[5][6][7]

PET/CBM
Further information: Commodore PET

The Commodore PET ("CBM" to the European market) series of home computers, which came with a built-on monitor, could only display monochrome characters, as it had no graphics capabilities at all, if one does not consider monochromatic "graphical" characters-based imagery.

VIC-20

The Commodore VIC-20 features an MOS Technology VIC chip which produces a 16-color composite video palette.[8] The palette lacks any intermediate shade of gray, and it has only 5 levels of luminance.

The VIC-20 lacks any true graphic mode, but a 22×11 text mode with 200 definable characters of 8×16 bits each arranged as a matrix of 20×10 characters is usually used instead, giving a 3:2(NTSC)/5:3(PAL) pixel aspect ratio, 160×160 pixels, 8-color "high-res mode" or a 3:1(NTSC)/10:3(PAL) pixel aspect ratio, 80×160 pixels, 10-color "multicolor mode".

Sample image

In the 8-color high-res mode, every 8×8 pixels can have the background color (shared for the entire screen) or a free foreground color, both selectable among the first eight colors of the palette. In the 10-color multicolor mode, a single pixel of every 4×8 block (a character cell) may have any of four colors: the background color, the auxiliary color (both shared for the entire screen and selectable among the entire palette), the same color as the overscan border (also a shared color) or a free foreground color, both selectable among the first eight colors of the palette.

Multicolor mode High-res mode

On some models of the system, there are nine levels of luminance:

Number — nameYUVNumber — nameYUV
0 — black000 8 — orange0.375−0.70710680.7071068
1 — white100 9 — light orange0.625−0.70710680.7071068
2 — red0.3125−0.38268340.9238795 10 — light red0.5−0.38268340.9238795
3 — cyan0.68750.3826834−0.9238795 11 — light cyan(*)0.750.3826834−0.9238795
4 — purple0.31250.70710680.7071068 12 — light purple0.50.70710680.7071068
5 — green0.5−0.7071068−0.7071068 13 — light green0.75−0.7071068−0.7071068
6 — blue0.2510 14 — light blue0.510
7 — yellow0.6875−10 15 — light yellow*1−10

But on other models, there are only five levels of luminance:

Number — nameYUVNumber — nameYUV
0 — black000 8 — orange0.5−0.70710680.7071068
1 — white100 9 — light orange0.75−0.70710680.7071068
2 — red0.25−0.38268340.9238795 10 — light red0.5−0.38268340.9238795
3 — cyan0.750.3826834−0.9238795 11 — light cyan*10.3826834−0.9238795
4 — purple0.50.70710680.7071068 12 — light purple0.750.70710680.7071068
5 — green0.5−0.7071068−0.7071068 13 — light green0.75−0.7071068−0.7071068
6 — blue0.2510 14 — light blue0.510
7 — yellow0.75−10 15 — light yellow*1−10

C-64

The MOS Technology VIC-II is used in the Commodore 64 (and Commodore 128 in 40-column mode), and features a 16-color YPbPr composite video palette.[9] This palette is largely based on that of the VIC, but it substitutes three colors by three levels of gray. When displayed over an analog NTSC composite video output, the actual resulting colors are more vivid.

Sample image Color test chart Color palette C64 palette on NTSC (Sony CXA2025 decoder matrix)
[10]

The Commodore 64 has two graphic modes: Multicolor and High Resolution.

In the Multicolor 160×200, 16-color mode, every cell of 4×8, 2:1 aspect ratio pixels can have one of four colors: one shared with the entire screen, the two background and foreground colors of the corresponding text mode character, and one more color also stored in the color RAM area, all of them freely selectable among the entire palette.

In the High Resolution 320×200, 16-color mode, every cell of 8×8 pixels can have one of the two background and foreground colors of the correspondent text mode character, both freely selectable among the entire palette.

16-color multicolor mode 16-color High-res mode

On most models of the Commodore 64, there are nine levels of luminance:

Number — nameYUVNumber — nameYUV
0 — black000 8 — orange0.375−0.70710680.7071068
1 — white100 9 — brown*0.25−0.92387950.3826834
2 — red0.3125−0.38268340.9238795 10 — light red0.5−0.38268340.9238795
3 — cyan0.6250.3826834−0.9238795 11 — dark grey0.312500
4 — purple0.3750.70710680.7071068 12 — grey0.4687500
5 — green0.5−0.7071068−0.7071068 13 — light green0.75−0.7071068−0.7071068
6 — blue0.2510 14 — light blue0.4687510
7 — yellow0.75−10 15 — light grey0.62500

C-16 and Plus/4

The MOS Technology TED was used in the Commodore 16 and Commodore Plus/4. It has a palette of 121 composite video colors[11] consisting of sixteen hues (including black and white) at eight luminance levels. Black is the same color at every luminance level, so there are not 128 different colors. On the Commodore Plus/4, twelve colors formed a "default" palette of sorts accessible through keyboard shortcuts;[12] these colors are underlined in the table below (RGB converted colors at a saturation level of 34%).

The Commodore 16 and Commodore Plus/4 have two graphic modes very similar to those of the Commodore 64: Multicolor and High Resolution.

In the Multicolor 160×200, 121-color mode, every cell of 4×8, 2:1 aspect ratio pixels can have one of four colors: two shared with the entire screen and the two background and foreground colors of the correspondent text mode character, all of them freely selectable among the entire 121-color palette (hue 0 to 15 and luminance 0 to 7 are set individually for any of them).

In the High Resolution 320×200, 121-color mode, every cell of 8×8 pixels can have one of the two background and foreground colors of the corresponding text mode character, both freely selectable among the entire 121-color palette (again setting both the hue and the luminance).

121-color Multicolor mode 121-color High-res mode
luma # 0 1 2 3 4 5 6 7
Y 0.1250.250.3750.50.6250.750.8751
hue # U V ........
0 — black00 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7
1 — white00 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7
2 — red−0.38268340.9238795 2,0 2,1 2,2 2,3 2,4 2,5 2,6* 2,7*
3 — cyan0.3826834−0.9238795 3,0* 3,1 3,2 3,3 3,4 3,5 3,6 3,7*
4 — purple0.70710680.7071068 4,0* 4,1 4,2 4,3 4,4 4,5 4,6* 4,7*
5 — green−0.7071068−0.7071068 5,0* 5,1 5,2 5,3 5,4 5,5 5,6* 5,7*
6 — blue10 6,0 6,1 6,2 6,3 6,4 6,5* 6,6* 6,7*
7 — yellow−10 7,0* 7,1* 7,2 7,3 7,4 7,5 7,6 7,7*
8 — orange−0.70710680.7071068 8,0* 8,1 8,2 8,3 8,4 8,5 8,6* 8,7*
9 — brown−0.92387950.3826834 9,0* 9,1* 9,2 9,3 9,4 9,5 9,6 9,7*
10 — yellow-green−0.9238795−0.3826834 10,0* 10,1* 10,2 10,3 10,4 10,5 10,6 10,7*
11 — pink01 11,0 11,1 11,2 11,3 11,4 11,5 11,6* 11,7*
12 — blue-green0−1 12,0* 12,1 12,2 12,3 12,4 12,5 12,6 12,7*
13 — light blue0.7071068−0.7071068 13,0* 13,1 13,2 13,3 13,4 13,5 13,6* 13,7*
14 — dark blue0.92387950.3826834 14,0 14,1 14,2 14,3 14,4 14,5* 14,6* 14,7*
15 — light green−0.3826834−0.9238795 15,0* 15,1 15,2 15,3 15,4 15,5 15,6* 15,7*

Notes

Tandy

Tandy Color Computer 3

The Tandy Color Computer 3 could display all of the modes of the Tandy Color Computer 1 and 2, except the Semigraphics modes, plus resolutions of 160, 256, 320, or 640 pixels wide by 192 to 225 lines from a palette of 64 colors. The 320 mode allowed 16 simultaneous colors, while the 640 mode allowed 4.

Thomson

For Thomson computers, a popular brand in France, the most common display modes are 320×200, with 8×1 attribute cells with 2 colors. The Thomson TO7 can only display the 8 "saturated" colors. The Thomson TO7/70 and Thomson MO5 have the 16 color palette shown below as a fixed palette (just like on C64 or MSX1). On later models, these 16 colors can be chosen from 4096 and other video modes are available, removing the block constraints but reducing either the color count or the horizontal resolution.

Saturated colors for Thomson SA color palette
0 — black
1 — blue
2 — red
3 — magenta
4 — green
5 — cyan
6 — yellow
7 — white

Examples
Example of 16 fixed color palette 1
0x0 0x1 0x2 0x3 0x4 0x5 0x6 0x7
0x8 0x9 0xA 0xB 0xC 0xD 0xE 0xF
Example of 16 fixed color palette 2
0x0 0x1 0x2 0x3 0x4 0x5 0x6 0x7
0x8 0x9 0xA 0xB 0xC 0xD 0xE 0xF
Example of 16 fixed color palette 3
0x0 0x1 0x2 0x3 0x4 0x5 0x6 0x7
0x8 0x9 0xA 0xB 0xC 0xD 0xE 0xF

BBC Micro

BBC Micro has 8 display modes, with resolutions like 640×256 (max. 2 colors), 320×256 (max. 4 colors) and 160×256 (max. 16 logical colors). No display modes have cell attribute clashes. The palette available has only 8 physical colors, plus a further 8 flashing colors (each being one of the eight non-flashing colors alternating with its physical complement every second), and the display modes can have 16, 4 or 2 simultaneous colors.

0 — black
1 — blue
2 — red
3 — magenta
4 — green
5 — cyan
6 — yellow
7 — white

Sinclair

ZX Spectrum
Main article: ZX Spectrum graphic modes

The ZX Spectrum (and compatible) computers use a variation of the 4-bit RGBI palette philosophy. This results in each of the colors of the 3-bit palette to have a basic and bright variant, with the exception of black. This was accomplished by having a maximum voltage level for the bright variant, and a lower voltage level for the basic variant. Due to this, black is the same in both variants.

The attribute byte associated to every 8×8 pixel cell dedicates (from LSB to MSB): three bits for the background color; three bits for the foreground color; one bit for the bright variant for both, and one bit for the flashing effect (alternate foreground and background colors evenly in time). So the colors are not selectable as indices of a true palette (there are not color numbers 8 to 15).

The color numbers can be employed with the following statements to choose:

  • BORDER n, the color for the surrounding area outside the pixel graphical area.
  • PAPER n, the background (pixel bit value of 0) color for an 8×8 pixel cell.
  • INK n, the foreground (pixel bit value of 1) color for an 8×8 pixel cell.
Simulated image Sample image
Color number Binary value BRIGHT 0 BRIGHT 1
0 000 black black
1 001 basic blue bright blue
2 010 basic red bright red
3 011 basic magenta bright magenta
4 100 basic green bright green
5 101 basic cyan bright cyan
6 110 basic yellow bright yellow
7 111 basic white bright white

SC-QL
256×256 512×256
black black
blue
red red
magenta
green green
cyan
yellow white
white
Further information: Sinclair QL

SAM Coupé

The 128 color master palette used by the SAM Coupé is produced via a unique method — it effectively contains 2 groups of 64 "RGB" colors of mildly different intensity, and ultimately derived from a 512 color space.[13] The closest equivalent in more popular and well-known machines would be the Commodore-Amiga's 64-color "Extra Half-Brite" mode (with 32 explicitly set colors using 5 bitplanes, which are displayed with full or half brightness depending on the bit setting of a 6th plane).

Two bits are used for each of Red, Green and Blue and give a similar result to a normal 6-bit RGB palette (as seen with the IBM EGA or Sega Master System); the seventh bit encodes for "brightness", which has a similar but more subtle effect to the Spectrum, increasing the output of all three channels by half the intensity of the lower bits of the main six (in this way, it does make a genuine 128 colors — rather than 127 colors with "two blacks" and only a 7-level grayscale). The layout of the byte that encodes each color is complicated and appears like a Spectrum color nybble transferred to a full byte's width, and an extra RGB bit-triplet then prefixed to it, with the MSB left unused.

SAM Coupé color palette and bitmask
0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F
0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F
0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F
0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F
0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F
0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 0x5A 0x5B 0x5C 0x5D 0x5E 0x5F
0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D 0x6E 0x6F
0x70 0x71 0x72 0x73 0x74 0x75 0x76 0x77 0x78 0x79 0x7A 0x7B 0x7C 0x7D 0x7E 0x7F
0x01 (low blue) 0x02 (low red) 0x04 (low green) 0x08 (brightness) 0x10 (high blue) 0x20 (high red) 0x40 (high green)

Amstrad

CPC series

The Amstrad CPC 464/664/6128 series of computers generates the available palette with 3 levels (not bits) for every RGB primary. Thus, there are 27 different RGB combinations, from which 16 can be simultaneously displayed in low resolution mode, four in medium resolution mode and two in high resolution mode.[14]

Simulations of actual images on the Amstrad's color monitor in each of the modes (160×200, 16 colors; 320×200, 4 colors and 640×200, 2 colors) follows. A cheaper green monochrome display was also available from the manufacturer; in this case, the colors are viewed as a 16-tone green scale, as shown in the last simulated image, as it interprets the overall brightness of the full color signal, instead of only considering the green intensity as might, e.g., the Philips CM8833 line.

2 colors 4 colors 16 colors 16-tone green scale
0 – Black (5) 1 – Dark blue (0,14) 2 – Blue (6) 3 – Dark red 4 – Dark magenta 5 – Violet 6 – Red (3) 7 – Magenta-red 8 – Magenta (7)
9 – Dark green 10 – Dark cyan (8) 11 – Cyan-blue (15) 12 – Dark yellow (9) 13 – Grey 14 – Light blue (10) 15 – Orange 16 – Pink (11, 15) 17 – Light magenta
18 – Green (12) 19 – Cyan-green 20 – Cyan (2) 21 – Yellow-green 22 – Light green (13) 23 – Light cyan 24 – Yellow (1, 14) 25 – Light yellow 26 – White (4)

The number in parentheses means the primary ink number for the Locomotive BASIC PEN, PAPER and INK statements (that is, "(1)" means ink #1 defaults to this color). Inks can also have a secondary color number, meaning they flash between two colors. By default, ink #14 alternates between colors 1 and 24 (blue and bright yellow) and ink #15 alternates between colors 11 and 16 (cyan-blue and pink). In addition, the paper defaults to ink #0 and the pen to ink #1, meaning yellow text on a dark blue background.

0 – Dark blue (1)
1 – Yellow (24)
2 – Cyan (20)
3 – Red (6)
4 – White (26)
5 – Black (0)
6 – Blue (2)
7 – Magenta (8)
8 – Dark cyan (10)
9 – Dark yellow (12)
10 – Light blue (14)
11 – Pink (16)
12 – Green (18)
13 – Light green (22)
14 – Dark blue (1)
15 – Cyan-blue (11)

MSX systems

Original MSX

The MSX compatible computers feature a Texas Instruments TMS9918 chip which uses a proprietary 15-color composite color encoded palette[15] plus a transparent color, intended to be used by the hardware sprites and simple video overlay. When used as an ordinary background color, it is rendered using the same color as the screen border.

The MSX series has two graphic modes. The MSX BASIC Screen 3 mode is a low-resolution mode with 15 colors, in which every pixel can be any of the 15 available colors. Screen mode 2 is a high-resolution mode with 15 colors, in which each of every eight consecutive pixels can be one of two out of the 15 available colors.

15-color screen mode 3 15-color screen mode 2
Number — nameYUVNumber — nameYUV
0 — transparentN/AN/AN/A 8 — medium red0.53−0.3770.868
1 — black000 9 — (light red)0.67−0.3770.868
2 — medium green0.53−0.509−0.755 10 — dark yellow0.73−0.7550.189
3 — light green0.67−0.377−0.566 11 — light yellow0.80−0.5660.189
4 — dark blue0.401−0.132 12 — dark green0.47−0.453−0.642
5 — light blue0.530.868−0.075 13 — magenta0.530.3770.491
6 — dark red0.47−0.3210.679 14 — gray0.8000
7 — cyan0.730.434−0.887 15 — white100
Note: The colors inside the parentheses are out of RGB gamut.

MSX2

The MSX2 series features a Yamaha V9938 video chip, which manages a 9-bit RGB palette (512 colors) and has some extended graphic modes. Although its graphical capabilities are similar, or even better than of those of 16-bit personal computers, MSX2 and MSX2+ (see below) are pure 8-bit machines.

Screen mode 6 is a 512×212-pixel mode with a 4-color palette chosen from the available 512 colors.

Screen modes 5 and 7 are high-resolution 256×212-pixel and 512×212-pixel modes, respectively, with a 16-color palette chosen from the available 512 colors. Each pixel can be any of the 16 selected colors.

Screen mode 8 is a high-resolution 256×212-pixel mode with an 8-bit color depth, giving a palette of 256 colors.[16] From the MSB to LSB, there are three green bits, three red bits, and two blue bits. This mode uses half of the available colors overall, and can be considered a palette in its own right.

4-color screen mode 6 16-color screen mode 5 256-color screen mode 8
Red #000000 #240000 #490000 #6D0000 #920000 #B60000 #DB0000 #FF0000
Green #000000 #002400 #004900 #006D00 #009200 #00B600 #00DB00 #00FF00
Blue #000000 #000055 #0000AA #0000FF

MSX2+

The MSX2+ series (released in 1988) features a Yamaha V9958 video chip which manages a 15-bit RGB palette internally encoded in YJK (up to 19,268 different colors from the 32,768 theoretically possible)[17] and has additional screen modes. Although its graphical capabilities are similar, or even better than of those of 16-bit personal computers, MSX2 (see above) and MSX2+ are pure 8-bit machines. YJK color encoding can be viewed as a lossy compression technique; in the RGB to YJK conversion, the average red and green levels are preserved, but blue is subsampled. As a result of every four pixels sharing a chroma value, in mode 12 it is not possible to have vertical lines of a single color. This is only possible in modes 10 and 11 due to the additional 16-color direct palette. This can be used to mix 16 indexed colors with a rich colorful background, in what can be considered a primitive video overlay technique.

Screen modes 10 & 11 – 12,499 YJK colors plus a 16-color palette. In this mode, the YJK technique encodes 16 levels of luminance into the four LSBs of each pixel and 64 levels of chroma, from −32 to +31, shared across every four consecutive pixels and stored in the three higher bits of the four pixels. If the fifth bit of the pixel is set, then the lower four bits of the pixel points to an index in the 16-color palette; otherwise, they specify the YJK luminance level of the pixel.

Screen mode 12 is similar to modes 10 and 11, but uses five bits to encode 32 levels of luminance for every pixel, thus it does not use an additional palette and, with YJK encoding, 19,268 different colors can be displayed simultaneously with 8-bit color depth.

Screen mode 10 & 11 Screen mode 12

Fujitsu

Fujitsu's FM-77 AV 40, released in 1986, uses an 18-bit RGB palette. Any 64,000 out of 262,144 colors can be displayed simultaneously at the 320×200 resolution, or 8 out of 262,144 colors at the 640×400 resolution.

IBM PC/XT and compatible systems
For the palettes of more advanced original IBM AT, IBM PS/2 and better PC compatibles hardware displays, please visit IBM PC/AT and compatible systems in the List of 16-bit computer color palettes article.

The original IBM PC launched in 1981 features an Intel 8088 CPU which has 8-bit data bus technology, though internally the CPU has a fully 16-bit architecture. It was offered with a Monochrome Display Adapter (MDA) or a Color Graphics Adapter (CGA). The MDA is a text mode-only display adapter, without any graphic ability beyond using the built-in code page 437 character set (which includes half-block and line-drawing characters), and employed an original IBM green monochrome monitor; only black, green and intensified green could be seen on its screen. Then, only the CGA had true graphic modes.

The IBM PC XT model, which succeeded the original PC in 1983, has an identical architecture and CPU to its predecessor, only with more expansion slots and a hard disk equipped as standard. The same two video cards, the MDA and the CGA, remained available for the PC XT, and no upgraded video hardware was offered by IBM until the EGA, which followed the introduction of the IBM Personal Computer/AT, with its full 16-bit bus design, in 1984.

CGA
Main article: Color Graphics Adapter

The Color Graphics Adapter (CGA) outputs what IBM called "digital RGB"[18] (that is, the R, G, B (and I) signals from the graphics card to the monitor can each only have two states: on or off). CGA supports a maximum of 16 colors. However, its 320×200 graphics mode is restricted to fixed palettes containing only four colors, and the 640×200 graphic mode is only two colors. 16 colors are only available in text mode or the "tweaked text" 160×100 mode. A different set of 16 colors is available in composite mode with an NTSC composite monitor. (Independent groups have also demonstrated much larger composite color sets—over 256 colors—on a composite monitor by the use of artifact color techniques. See Color Graphics Adapter#High color depth.)

The full standard RGBI palette is a variant of the 4-bit RGBI schema. Although the RGBI signals each have only two states, the CGA color monitor decodes them as if RGB signals had four levels. Darker colors are the basic RGB 2nd level signals except for brown, which is dark yellow with the level for the green component halved (1st level). Brighter colors are made by adding a uniform intensity one-level signal to every RGB signal of the dark ones, reaching the 3rd level (except dark gray which reaches only the 1st level), and in this case yellow is produced as if the brown were ordinary dark yellow.

0 — black 8 — dark gray
1 — low blue 9 — high blue
2 — low green 10 — high green
3 — low cyan 11 — high cyan
4 — low red 12 — high red
5 — low magenta 13 — high magenta
6 — brown 14 — yellow
7 — light gray 15 — white

The color numbers above are not arbitrary; they are based on the following bitmask:

Binary Decimal Color
1000 8 intense, high, or bright
0100 4 red
0010 2 green
0001 1 blue

*A few earlier non-IBM compatible CGA monitors lack the circuitry to decode color numbers as of four levels internally, and they cannot show brown and dark gray. The above palette is displayed in such monitors as follows:

0 — black 8 — black*
1 — low blue 9 — high blue
2 — low green 10 — high green
3 — low cyan 11 — high cyan
4 — low red 12 — high red
5 — low magenta 13 — high magenta
6 — low yellow* 14 — yellow
7 — light gray 15 — white
  • 16-color palette modes
16-color, 80×50 mode 16-color, 160×100 mode
  • 2-color palette mode

In the 640×200 graphic mode (BIOS mode number 6), every pixel has only a single bit. A value of 0 is always black, while a value of 1 is the color set in the bits 0 to 3 (bit3=I, bit2=R, bit1=G, bit0=B) of the CRT Color Selector Register (in 3D9h). The foreground color can be set with a call to the function 0Bh of the BIOS's INT 10h. The default foreground color is white.

2-color palette mode 0 — black 1 — [user-defined]
  • 4-color palette modes

In the 320×200 graphics mode, every pixel has two bits. A value of 0 is always a selectable background-plus-border color (with the same register and/or BIOS call used for the foreground color in the 640×200 graphic mode; black by default), and the three remaining values 1 to 3 are indices to one of the predefined color palette entries.

The selection of a palette is a bit complex. There are two BIOS 320×200 CGA graphics modes: modes 4 and 5. Mode 4 has the composite color burst output enabled (in the Mode Control Register at I/O address 3D8H, bit 2 is cleared), and mode 5 has it disabled (the same bit 2 is set). Mode 5 is intended mainly for a monochrome composite video monitor, but because of a specific intentional feature of the CGA hardware, it also has a different palette for an RGBI color monitor. For mode 4, two palettes can be chosen: green/red/brown and cyan/magenta/white; the difference is the absence or presence of the blue signal in all three colors. (The palette is selected with bit 5 of the Color-Select Register at I/O address 3D9h, where the bit value 1 selects the cyan/magenta/white palette [a/k/a "palette #1" because it is the BIOS default] and 0 selects the green/red/brown palette [a/k/a "palette #2"]. This bit can be set using BIOS INT 10h function 0Bh, subfunction 1.) The palette for BIOS video mode 5 is always cyan/red/white: blue is always on, and red and green each are controlled directly by one of the two bits of the pixel color value. For each of these three palette options, a low or high intensity palette can be chosen with bit 4 of the aforementioned Color-Select Register: a value of 0 means low intensity and 1 means high intensity. (No BIOS call exists to switch between the two intensity modes.) The selected intensity setting simply controls the "I" output signal to the RGBI monitor for all colors in the palette. As a result, the green-red-brown palette appears as bright-green/bright-red/yellow when high intensity is selected. The combination of color-burst enable/disable selection, palette selection, and intensity selection yields a total of 6 different possible palettes for CGA 320×200 graphics.

Mode 4, palette #1 Mode 4, palette #2 Mode 5
Low intensity
High intensity
Simulated Grayscale
Mode 4, palette #1, low intensity 0 — [user-defined] 1 — cyan 2 — magenta 3 — light grey
Mode 4, palette #1, high intensity 0 — [user-defined] 1 — bright cyan 2 — bright magenta 3 — bright white
Mode 4, palette #2, low intensity 0 — [user-defined] 1 — green 2 — red 3 — brown
Mode 4, palette #2, high intensity 0 — [user-defined] 1 — bright green 2 — bright red 3 — yellow
Mode 5, low intensity 0 — [user-defined] 1 — cyan 2 — red 3 — light grey
Mode 5, high intensity 0 — [user-defined] 1 — bright cyan 2 — bright red 3 — white
Simulated grayscale 0 — black 1 — light grey 2 — dark grey 3 — white

PCjr and Tandy 1000 series

The IBM PCjr features a "CGA Plus" video subsystem, consisting mainly of a 6845 CRTC and an LSI video chip known as the "Video Gate Array", that can show all 16 CGA colors simultaneously on screen in the extended low-res graphic modes. The near-compatible Tandy 1000 series features almost 100% PCjr-compatible video hardware implemented in a Tandy proprietary chip. This graphics adapter is better known by the name Tandy Graphics Adapter, because the PCjr was short-lived but the Tandy 1000 line was quite popular for many years. The video mode capabilities of early-model Tandy 1000 computers are exactly the same as the PCjr's. (Later Tandy 1000 models featured "Tandy Video II" hardware which added a 640x200 16-color mode but surrendered PCjr hardware register-compatibility for CGA register-compatibility.)

The PCjr adds three video modes to the CGA mode set: 160×200 16-color "low-resolution" graphics, 320×200 16-color "medium-resolution" graphics, and 640×200 4-color "high-resolution" graphics. All PCjr/Tandy 1000 graphics modes can reassign any color index to any palette entry, allowing free selection of all palette colors in modes with fewer than 16 colors (including the plain CGA modes) and enabling color cycling effects in all modes. The PCjr also offers a graphics blink function which causes 8 colors to alternate between the low and high halves of the 16-color palette at the text blink rate. (A PCjr must be upgraded with a PCjr-specific internal 64 KB memory expansion card in order to use the latter two of these modes or any 80-column text mode. Tandy 1000 base models can use all video modes.)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Side-by-side comparison

Since there are many 8-bit computers to compare, a comparison table has been compiled to make comparing the systems easier.

8-bit computer color palettes
Computer(s) Picture sample(s) Entire palette(s) Number of colors on screen Resolution(s)
Apple II Hi-res:

Lo-res:

Hi-res:

Lo-res:

6 (high resolution mode), or 16 (low resolution mode) 280x192 in high resolution or 40x48 in low resolution
Atari 8-bit line Mode 15 (with color interrupts and MCS): 9 colors per scanline on mode 15 via masking the 4 sprites for colors, and interrupts. Ranges from 320x192, with 1 color, to 80x192 with 9 colors.
Mattel Aquarius 16 colors 40x24 characters
BBC Micro
Ranges from 2 to 8 colors Ranges from 640x256 to 160x256
Commodore 64 High res mode:

Multicolor mode:

 All 16 colors can be present in one screen. However, 4 can be present in one 4 x 8 cell in multicolor mode, and three of those colors must be shared. 2 colors can be present in every 8 x 8 cell in high resolution mode. 320 x 200 in high resolution mode

160 x 200 in multicolor mode

See also

References
  1. "The Laboratorium : Why Did the Apple II Have Six Colors?". laboratorium.net.
  2. http://www.downloads.reactivemicro.com/Public/Users/Grant_Stockley/Apple2MoreColorsBYTEJun1979.pdf
  3. http://apple-2.com/pdf/bbfront.png
  4. http://atariage.com/forums/uploads/monthly_07_2014/post-3819-0-00736800-1405189983.jpg
  5. "Spectrum vs C64" match, Italy, 1985 "The blue was simply stunning. The red made the room warm. The magenta was like an exotic icecream. The green was something like freshly rained grass. The cyan was like the ocean's water. The yellow seemed got off from a fluorescent pen. And the white was clean and soft ... The C64 screen first became black (but not too much), then became white (an exaggerated white), then orange, then something like bluish, then a vaguely magenta, then a poor water-greenish, then a bright bluish, then a faded yellow, then a weird brown, and then a light gray... well, all "pastel-like" colours"
  6. ZX Spectrum vs Commodore 64 – the playground argument settled "you will remember the playground taunts regarding washed out colours, peeks and pokes and the relative lack of software in your local WH Smith"
  7. ZX Spectrum vs Commodore 64 "the C64 had muddy colours...but whack up the colour saturation of your TV and most of that was alleviated"
  8. "The 6561 VIC chip". Archived from the original on 2010-04-01. 090420 fpgaarcade.com
  9. Philip 'Pepto' Timmermann (12 March 2001). "All you ever wanted to know about the colors of the commodore 64". pepto.de.
  10. "C64 Emulator Palette from my NTSC 1702 - Page 2 - Commodore 64 (C64) Forum". lemon64.com.
  11. Commodore Hacking #12 : Talking to TED Archived 2009-01-05 at the Wayback Machine
  12. Color codes Archived 2007-09-27 at the Wayback Machine
  13. Cooke, Simon; et al. (1994). "The Graphics Hardware" (PDF). The Unofficial SAM Coupé Technical Manual (sampler edition). Σntropy. pp. 16–20. Retrieved 5 February 2013.
  14. "The Amstrad CPC Firmware Guide"
  15. VDP Registers 00h-07h: Basic MSX1/MSX2 Video Registers from "Portar MSX Tech Doc" Archived 2007-11-30 at the Wayback Machine
  16. Bits M1-M5 of VDP register 0 and 1: Video Screen modes, Screen 8 from "Portar MSX Tech Doc" Archived 2007-11-30 at the Wayback Machine
  17. "The MSX Plaza". msx-plaza.eu.
  18. Richard Wilton, Programmer's Guide to PC & PS/2 VIDEO SYSTEMS, 1987, Microsoft Press.
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