I know. But I only have cycle info for a 4 MHz. I thought the calculators used RC pairs anyway, which means it technically clocks at ~6 MHz +- about 20% for capacitor tolerance. TGaArdvark@aol.com wrote: > > > 2.5 us v.s. 3 us on a 4 MHz z80? > > It's 6 MHz. -- Bryan Rittmeyer mailto:bryanr@flash.net http://www.bridges.edu/horizon/