Changes
A complicated kernel is aware of exactly when different pushed values will be referenced and updates them live — e.g. dynamically changing the contents of a sprite that is repeated three times to make it look like three different sprites with a fixed spacing. Using the two sprites together in this manner is commonly used to produce a six-digit score line. Changing the 20 pixels of provided background information so that all 40 pixels of drawn background are distinct is also relatively common.
The Atari uses a cut-down version of the [[6502 ]] with a restricted number of address lines. As a result the window for cartridges is only 4kb. Therefore several on-cartridge banking schemes exist. Only one cartridge is known to try to extend the hardware beyond greater addressing: Pitfall II provides some additional timers and an additional built-in sound generator. The processor copies one PCM sample from the cartridge to the TIA each line.
An advantage of the primitive hardware that ties the TIA directly to the task of composite video generation is an unexpectedly large colour palette: 128 colours in its native NTSC. This is because each 7-bit colour selection is converted directly to a 4-bit phase offset applied to the colour subcarrier and a 3-bit amplitude applied to the luminance output, allowing two very cheap bits of electronics to produce a wide range of colours at the cost of those colours being dictated by the mathematics rather than by any human judgement.
[[Category:Non CPC Computers]]
