Pixel

Pixel is a contraction of Picture Element. A single, indivisible unit that makes up an image when used in conjunction with many (perhaps thousands or millions) other pixels. Typically, the visible part of the Mega Drive screen consists of 71,680 pixels, since it has a display resolution of 320×224.

Units

• 1 megapixel (MPixel) = 1 million pixels
• 1 gigapixel (GPixel) = 1 billion pixels (1000 MPixels)

Fillrate

The term fillrate refers to the number of pixels a video card or graphics chipset can render in a second, and the number of pixels it can write to video memory. This is also known as the rendering fillrate. Traditionally, fillrate was dependent on video memory bandwidth, the rate at which bytes can be written to, or read from, video memory, but this is no longer the case with modern GPU.

The term effective fillrate is used in reference to tilemap/scanline/tiled rendering engines which minimize the amount of pixels that need to be drawn on screen, read from memory, or written to memory, by rendering graphics data as tiles rather than pixels, thus reducing fillrate and bandwidth requirements to a small fraction or percentage of what would be required from traditional bitmap/framebuffer rendering engines. The fillrates of tiled rendering engines are usually measured in terms of tiles, rather than pixels, thus the term effective fillrate refers to the equivalent amount of pixels that would be required from a traditional bitmap/framebuffer rendering engine to display the same amount of tiles as a scanline/tiled rendering engine. Tiled rendering engines are supported by all Sega consoles, and most Sega arcade systems, from the G80 (1981) to the Hikaru (1999) and NAOMI 2 (2000).

The units used to measure fillrate:

• 1 megapixel/sec (MPixel/s) = 1 million pixels per second
• 1 gigapixel/sec (GPixel/s) = 1 billion pixels per second (1000 MPixels/s)

Fillrates for Sega consoles:

• SG-1000 (1983) — 3.579545 MPixels/s (read), 1.789772 MPixels/s (write)
• Master System (1985) — 5.369317 MPixels/s (read), 1.789772 MPixels/s (write)
• Mega Drive (1988) — 6.934358 MPixels/s (read), 6.41376 MPixels/s (write), 6.934358–36.325644 MPixels/s (effective tile fillrate)
  • CD (1991) — 6.934358 MPixels/s (read/write), 6.934358–36.325644 MPixels/s (effective tile fillrate)
  • 32X (1994) — 18.181818 MPixels/s (32,768 colors), 36.363636 MPixels/s (256 colors)
• Saturn (1994)
  • VDP1 — 28.6364 MPixels/s (32,768 colors), 57.2728 MPixels/s (256 colors)
  • VDP2 — 14.21875–114.5456 MPixels/s (bitmap fillrate), 125.82912–503.31648 MPixels/s (effective tilemap fillrate)
• Dreamcast (1998) — 3.2 GPixels/s (opaque polygons), 500 MPixels/s (translucent polygons)

For the fillrates of Sega arcade systems, see List of Sega arcade systems.

Texel

A texel (texture element or texture pixel) is the fundamental unit of texture space. Textures are represented by arrays of texels, just as pictures are represented by arrays of pixels.

Units

• 1 megatexel (MTexel) = 1 million texels
• 1 gigatexel (GTexel) = 1 billion texels (1000 MTexels)

Texture Fillrate

• 1 megatexel/sec (MTexel/s) = 1 million texels per second
• 1 gigatexel/sec (GTexel/s) = 1 billion texels per second (1000 MTexels/s)

The texture fillrate was the same as the rendering fillrate for Sega consoles up until the Sega Saturn. The Sega Dreamcast has differing fillrates for rendering and texturing. For Sega arcade systems, it varies depending on the hardware.