Re: Why So Slow?
I was wondering this first when I realised that the original AT motherboard ran at 5MHz and was not much smaller (13.8" x 12").
I think the PCB size itself does not necessary limit the speed so much. However, if the CPU is simply a transistor for transistor substitution from the die to the PCB without any redesign, simply scaling things up might well scale up parasitic capacitances and time constants. Also, the 6502 used some dynamic registers (essentially single byte DRAMs) to reduce transistor count - scaling up the storage capacitor might also limit the clock speed by increasing the charge/discharge time constant.
I presume the 1960s transistor based computers running in the MHz range were designed on the macro-scale to control these capacitances in the first place.
Biting the hand that feeds IT
