Changes
/* Video */
*The Spectrum's video ram takes approx 6K. The Amstrad's video ram takes 16K (approx 12K when screen is reduced).
*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.
*'''Amstrad CPC''' has a '''palette of 27 colours.''' And 3 different [[Video Modes]]. 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 colours in 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.''' Yet with the Attributes limitation (2 colours per 8x8pix squares...) *The Amstrad can only do the same in mode 0, but this has wider pixels (approx 2x1 ratio). If the CPC's mode 1 resolution is chosen, it is not possible because only 4 colours can be chosen. Anyway some raster interrupt tecniques enable to mix (with horizontal limits) different modes or even to change the palette so more than the theoricall inks number can be displayed on the full screen. Such way was actually often used in many Speccy ports.
*Normally Spectrum graphics is stored in 2 colours, which means 8 pixels for each byte. In Amstrad mode 1, each byte defines 4 pixels. So for the same graphics you often need twice the RAM on the Amstrad. (This is a case where graphics without transparency are used). If transparency is used, then the amount of data can be the same.
