The [[GBZ80]] (Sharp SM83) that powers the original [[Nintendo GameBoy]] is an in-between the [[Intel 8080]] and Z80. [https://gbdev.io/pandocs/CPU_Comparison_with_Z80.html Source]
The ASCII [[R800]] that powers the MSX TurboR is a seriously beefed up version of the Z80.:
* The ALU of the R800 is 16-bit instead of 4-bit for the Z80. This change allows instructions that were being executed in 4 clocks to be done in 1 clock.
* The instruction set of the R800 is almost identical to the Z80. Only 2 instructions have been added: MULUB and MULUW. And many of the undocumented instructions of the Z80 were made official.
[[Zilog]] itself offers the [[eZ80]] processor, a binary-compatible upgrade of the Z80, which runs at up to 50MHz but performs like a 150MHz Z80 due to being 3 times faster at the same clock speed.