ZX Spectrum
The ZX Spectrum was a British 8 bit computer from Sinclair Research based on a Z80 CPU, like the Amstrad CPC, and was released earlier. It is known affectuously as the "Speccy".
It was in many respect like the Amstrad to the point that so many Amstrad CPC games were in fact ZX Spectrum ports.
But The main difference between those 2 systems was the Video Display method.
The good Old Speccy is well known for his dreaded "Colour Clashes" thanks to it ability to only display 2 bits graphics (2 colours per caracters).
It could of course display more than 2 colours on the screen thank to the technic called colour attributes (a grid is applied to the screen to give "attributes" to each caracters).
The Speccy Video Ram used only 6Ko per screen.
The Amstrad CPC was 16Ko.
As a result, the Amstrad seemed less efficient concerning animation because the Video Ram was far more demanding. But a proper coding could give better result than simply porting codes from a speccy.
The ZX Spectrum Killed the Amstrad CPC...sort of.
Also Amstrad bought the ZX Spectrum range and released it's own ZX spectrum range. And this also killed the Amstrad CPC commercially.
As an exemple, the ZX Spectrum 2+ (equivalent to the CPC 464) released by Amstrad did have 128Ko Ram.
CPC's Speccy ports were not alway that bad.
Somme of them managed to be quite good despite all.
Exemples are R-Type or PacMania.
But those games usually had the same kind of flaws :
--Monocolor : The 2 bit codes for the Graphics (sprites, tiles) meant that those games were often monochromatic. But the developpers cheated this by puting extra colours in the HUD often thanks to Rasters interrupts. Of course those Extra colours were useless indeed.
--Smaller screen : To match the actual resolution of the Speccy, those games used the Mode 1 and reduced the screen resolution (which was lower on the Speccy)
Typical exemples : Black tiger, Pac-Mania.