Changes
/* Machine comparisons */
*Spectrum and Amstrad both have a Z80 CPU.
* The CPU runs at a similar speed (3.5Mhz in Spectrum, 4Mhz in Amstrad) (Note, both systems do not run at optimum speed due to waits inserted by the video hardware).
*Spectrum and Amstrad both have a bitmapped display.
*The Spectrum 48k can't do double buffering in hardware, the Amstrad can. The Spectrum 128K can do double buffering. On the Amstrad and Spectrum 128K you can use hardware double buffering, but then you need to sacrific twice as much video ram (e.g. For Amstrad: 2 x 16K).
*The Spectrum has a fixed palette of 15 colours (8 colours with bright versions of each making 15 in total - LIGHT black is still black). Amstrad has a palette of 27 colours. In mode 0 you can choose 16 of these, in mode 1 you can choose 4 of these, in mode 2 you can choose 2 of these. The Amstrad's palette includes equivalent colours that match closely the Spectrum's colours.
*The Spectrum's screen is "attribute" based. Each 8x8 cell can be assigned a background and foreground colour (and both colours must either be non-bright or bright). There is also the choice to flash the coloursin each cell (the flash is a fixed rate and alternates between paper/pen and pen/paper). This colouring results in "attribute/colour clash" on the Spectrum. The Amstrad's screen doesn't have this, and there is no restriction on how the colours can be placed. * The colours of each 8x8 "attribute" cell is defined by a block of ram following the Spectrum's bitmapped screen, each byte represents one cell and each byte defines paper colour, pen colour, flash enabled and bright enabled. The colours for the pens on the Amstrad are defined by writing to the Gate-Array's palette I/O registers. The pens are read from the pixel data and the resulting colour is looked up in the palette registers.
*The Spectrum can display all 15 colours on the screen. The Amstrad can only do the same in mode 0, but this has fatter pixels. If the CPC's mode 1 resolution is chosen, this is not possible because only 4 colours can be chosen.
====Colours & Colour Clash====
The cell based colouring used on the Spectrum has its disadvantages. [[image:clash.png|right|thumb|Colour clashing in Knight Tyme. Observe the appearance of the character sprite as it merges with the background. (Background colours have priority here in this game.)]]
When moving a sprite over a background, or a sprite over another sprite, and if both have colours you have to decide which colours take priority.
It is not possible to have all the colours together because of the colour limitation within each 8x8 cell.
* If cell based movement is done, then CPC version has the same movement whereas it could be pixel perfect on CPC.
* If black border is used, CPC has the unnecessary black border.
* Because the The CPC can't replicate the Spectrum's colour attribute system in mode 1, this means the mode 1 version has even less colours than the Spectrum version. The CPC version has 4 colours, compared to up to 16 possible colours on the Spectrum.
What they should do for CPC:
