A chip with a girl's name?!

One of the three legendary custom chip in Commodore's Amiga line of computers. The name derives from it being a Display ENcoder. The original display encoder found on the Amiga 1000 was called Daphne, the Denise name came into being with the Amiga 500 and 2000. The Denise had a number of different graphics modes, including resolutions of 320x256 (lo-res), 640x256 (hi-res), 320x512 (lo-res interlaced) and 640x512 (surprise! -- hi-res interlaced).

Capabilities

Since Amigas were built to output to TV displays or video recorders as well as computer monitors, the Denise could do both PAL and NTSC output. The vertical resolutions listed above are for PAL output (since this noder is European), NTSC output had 200 vertical lines rather than 256 in normal mode, and 400 rather than 512 in interlaced mode. In lo-res, Denise could output displays of 2, 4, 8, 16, 32, 64 (EHB) and 4096 (HAM) colours, and featured a palette of 4096 colours (popular PCs at the time could go all the way up to 16 colours, if they had cool and expensive graphics cards).

The two special colour modes, EHB and HAM, took advantage of some special features in the chip. EHB stands for Extra-HalfBrite, and created a 32 colour palette with 32 extra indexes that are half-brightness copies of the first 32. HAM (Hold And Modify) mode used a 16-colour palette, and used some funky display tricks to allow use of all 4096 colours, at the expense of some image quality (each pixel that had a colour index outside of the first 16 discoloured two pixels to its right).

Later refinements

A later version, the so-called Super Denise featured on ECS (Enhanced Chip Set) Amigas (the Amiga 500+, Amiga 600 and Amiga 3000), could do even higher resolutions, going up to 1280x512 pixels at up to 16 colours. The Denise was finally replaced by the Lisa in AGA (Advanced Graphics Array) Amigas like the Amiga 1200 and Amiga 4000. Lisa had 16.7 million colours and a few more resolution options. Denise and "her" successor Lisa were discontinued when Amiga went under, the various Amiga knockoffs (like the Draco) did not use the characteristic custom-chip design of the original Amiga.

References

  • http://amiga.emugaming.com/customchips.html
  • http://home.austarnet.com.au/wardy/amiga.html

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