*[[FDC|765 FDC]] is bloated with 40 pins, compared to 28 pins for the WD1772 FDC used in the [[Atari ST]]. It is also a black box internally, while the [[C64]] uses a regular 6502 (with its own ROM and RAM) as FDC.
And unlike the [[ZX Spectrum ]] and the [[MSX]], on the Amstrad CPC and Plus things can go catastrophically wrong if bus timings are not accurately emulated.
Thankfully, many tools and tests exist to help emulation authors.