Key games here are : Saboteur 2 (run fine with "MEM_WR=slow", does freeze with "MEM_WR=quick") and Arkanoid II (run fine with "MEM_WR=quick", too slow using "MEM_WR=slow")
[http://www.cpcwiki.eu/forum/programming/cpc-z80-commands-and-how-long-they-take/40/ CPC Z80 Commands and how long they take...]
=== Test of a real Zilog 80 ===