old MAC's

"Bill Layer" <b.layer(a)vikingelectronics.com> wrote: No. The 68040 (all variants including the LC and EC) require a double-speed clock input, but the internal pipeline does NOT execute at the double speed. A 68040 with 33 and 66 MHz clock inputs actually runs at 33 MHz. Motorola documentation is very clear on this. As soon as Motorola atarted sending out "advanced information" data sheets it became apparent that this would cause a lot of confusion. Think of it more like a 2 MHz 8080 that requires a two-phase clock. It does some internal things on one phase and some on the other. The 68040 is similar but derives the phases internally from a double-speed clock. And before someone tries to "correct" me, yes, I do know that the 68040 is CMOS, and does not use traditional two-phase NMOS logic structures like the 8080. The reason it needs multiple phases is simply due to the way the pipeline is structured. More modern high-end microprocessors have internal PLLs or DLLs to synthesize the various necessary internal timing signals so that there is only one clock input, and usually that clock input is at a much lower frequency than the pipeline.