Changes
/* Machine comparisons */
They have a similar screen size. Amstrad's screen can be reduced in size to match the Spectrum's (256x192). Normal display size on Amstrad is 320x200.
Spectrum (128K model and later) and Amstrad both have an AY-3-8912 sound chip. (1.7Mhz clock for AY in spectrum, 1.0Mhz clock for AY in Amstrad). (Spectrum 48K had a 1-bit beeper sound. It is possible to translate this into similar AY sounds)
The size and aspect of the pixels in the Spectrum's bitmapped display are comparable to the pixels in Amstrad's mode 1 bitmapped display.
The Spectrum 48k can't do double buffering in hardware, the Amstrad can. (To fix this problem on Spectrum they stored a bitmap in ram which they drew to, and then wrote changes to the screen). On the Amstrad you can use hardware double buffering, but then you need to sacrific twice as much video ram (e.g. 2 x 16K).
The Spectrum has a fixed palette of 16 colours (8 colours with 8 bright versionsof each making 16 in total). 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 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. The Amstrad's screen doesn't have this , and there is no restriction on how the colours can be placed as you choose.
The Spectrum has 1 interrupt per 50Hz frame, the Amstrad has 6 in fixed locations through the frame.
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.
Neither had hardware sprites, therefore you have to use the CPU to both draw and erase the sprites.
Amstrad has hardware scrolling, Spectrum does not.
===Consequences===
The Amstrad CPC was one of the best 8-bit computers of its time in terms of graphical capabilities. But those advanced capabilities had an impact on CPU resources. As so many games were ported from the Spectrum, a machine with decidedly lower visual specs, the Amstrad range could hardly benefit from its main advantage while lack of optimization meant that aspects as scroll or playing area fared even worse than the Spectrum versions. You have to remember that Spectrum had less resources taken by Video RAM, so could handle animation or scrolling more easily. It is also a misconception to believe the screen was downsized in those games to gain processor resources. It was only done to use the Speccy graphics more easily, and we can doubt the code was (re-)designed so such a screen reduction would even gain CPU resources.
Interestingly, games in Mode 1 could have been good despite the lack of colours, if only those colours were used properly more often.
