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 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.(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 is are comparable to the pixels in Amstrad's mode 1 bitmapped display.
The Spectrum's video ram takes approx 6K. The Amstrad's video ram takes 16K (approx 12K when screen is reduced).
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 versions). 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. The Amstrad's screen doesn't have this restriction, 4 the colours can be chosen from a palette of 27, and can be placed as you choose.
The Spectrum has 1 interrupt per 50Hz frame, the Amstrad has 6 in fixed locationsthrough the frame.
===Consequences===
On the other hand, as mentioned before, those games weren't always bad. Games with no need of scrolling and with re-coded graphics could actually be good.
=The killer-list of the infamous speccy ports=