I run my Olivetti M380XP9, originally with i386-33, with a Cyrix 486DLC plus Cyrix FPU. It does not have the speed of a real 486-33, but I like that machine. There is only one thing, when I enable all features of the Cyrix CPU, Windows 3.11 does not detect the Sound Blaster Pro card, so no sound. In DOS mode no problem, all games, demos, mod players etc play sound nice with all CPU speed features on. To have sound in Windows, I have to disable all these optimisations, but the PC is still a bit faster as with a i386-33.