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Simulation of ZX Spectrum graphics output on a PAL TV set. The original ZX Spectrum computer produces a one bit per pixel, bitmapped colour graphics video output. A composite video signal is generated through an RF modulator, and was designed for use with contemporary 1980s television sets.
Mode 4 - 256×192 graphics with 16 colours; Mode 3 - 512×192 graphics with 4 colours; Mode 2 - 256×192 graphics with 2 colors (from 16) for each 8-wide block of pixels; Mode 1 - 256×192 graphics with 2 colors (from 16) for each 8x8 block of pixels (matching the display of the ZX Spectrum for backwards compatibility)
The ZX Spectrum (UK: / z ɛ d ɛ k s /) is ... a graphics mode that required less than 7 kilobytes of memory and implemented it on the ULA. ... in a broad agreement ...
The ZX Spectrum used 6144 bytes for the bitmap, with one byte representing eight pixels, and used 768 bytes for the colour attributes. This gives a total of 6912 bytes for the entire graphics display, a relatively small total for a computer of the Spectrum's era with "colour" capabilities.
A Mode 3 or Mode 4 screen uses four times as much RAM as a ZX Spectrum Mode 1 display, so four times the work had to be done in the same time when updating it. A small compensation was the straightforward arrangement of colour pixels in this memory, instead of the ZX Spectrum's more limited display and attributes memory.
The coarse, low-resolution graphics display mode works differently, as it can output a pattern of dots per pixel to offer more color options. These patterns are stored in the character generator ROM and replaces the text character bit patterns when the computer is switched to low-res graphics mode.
For compatibility purposes, the original 256 x 192 ZX Spectrum mode is available. New graphics modes offer expanded abilities: 640 x 200 mode, with 2 out of 16 colors per 8x1 pixels. The Profi offers a similar mode, but the ATM can use the full 16 colour set for both ink and paper.
His main contribution was the design of the graphics mode using less than 7 kilobytes of memory. He also participated in the preliminary stages of the development of the ZX Microdrive. [2] Altwasser left Sinclair at the beginning of May 1982 to establish his own company, along with Steve Vickers, author of the Spectrum's ROM firmware and manual