Extra Half-Brite mode is a planar display mode of the Commodore

Commodore International

Commodore is the commonly used name for Commodore Business Machines , the U.S.-based home computer manufacturer and electronics manufacturer headquartered in West Chester, Pennsylvania, which also housed Commodore's corporate parent company, Commodore International Limited...

 Amiga

Amiga

The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...

 computer. It uses six bitplanes (six bits/pixel). The first five bitplanes index 32 colors selected from a 12-bit color space

RGB color model

The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...

 (4096 possible colors). If the bit on the sixth bitplane is set the display hardware halves the brightness of the corresponding color component. This way 64 simultaneous colors are possible (32 arbitrary colors plus 32 half-bright components) while only using 32 color registers. The number of color registers is a hardware limitation of pre-AGA

Advanced Graphics Architecture

Advanced Graphics Architecture is the third generation Amiga graphic chip set, first used in the Amiga 4000 in 1992. AGA was codenamed the Pandora chipset by Commodore International internally....

 chipsets used in Amiga computers.

Some contemporary game titles and animations used EHB mode as a hardware-assisted means to display shadows or silhouettes. EHB was also often used as general-purpose 64 color mode with the aforementioned restrictions.

Some early versions of the first Amiga, the Amiga 1000

Amiga 1000

The A1000, or Commodore Amiga 1000, was Commodore's initial Amiga personal computer, introduced on July 23, 1985 at the Lincoln Center in New York City....

, sold in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 lack the EHB video mode, which is present in all later Amiga models.

EHB Sliced Mode

With EHB palette switching, it is possible to produce yet more colors in a single image; this can be achieved by splitting the image into multiple horizontal blocks (slices), between which the color registers are modified during the vertical scan. This is not an official graphics mode, but a software technique made possible by the hardware. For example, by switching the palette eight times during a vertical scan, it is possible to produce up to 512 on-screen colors. Unlike the 4096 color HAM

Hold-and-Modify

Hold-And-Modify, usually abbreviated as HAM, is a display mode of the Commodore Amiga computer. It uses a highly unusual technique to express the color of pixels, allowing many more colors to appear on screen than would otherwise be possible....

 mode, this technique places no restrictions on color combinations between horizontally adjacent pixels. For example, moving parts of the image (within slice) do not require complex operations.

Comparison to EGA

Although the IBM PC

IBM PC

The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...

 Enhanced Graphics Adapter

Enhanced Graphics Adapter

The Enhanced Graphics Adapter is the IBM PC computer display standard specification which is between CGA and VGA in terms of color and space resolution. Introduced in October 1984 by IBM shortly after its new PC/AT, EGA produces a display of 16 simultaneous colors from a palette of 64 at a...

 (EGA) standard offers a 64 color space, it only allows 16 simultaneous colors (16 out of 64). EHB allows 32 colors out of 4096 plus their half-bright counterparts (32 + 32 out of 4096).

External links

• Animated demo using Halfbrite mode (requires Java)