If anyone has investigated the latest USB technology whcih allows super speed data transfer, you need to stop and think about how that might be occurring.

Under normal operation the device containing our microprocessor is connected to a dumb peripherial. The clock that controls the data transfer is the off chip crystal clock. That clock is slow which is why it is jacked up to a much higher frequency before it gets to be the cpu clock.

Now you connect your device containing a microprocessor to another device that is not dumb. It has its own clock. And that clock is running at fast speeds. Do you attempt to use the off chip crystal clock to control data transfer or would you like to use the perhipherial device's clock?

If you look at the USB transfer speeds under various specifications you will see they are increasing substantially. Currently Super Spped is 5GBPS. An update is coming with standard of 10GBPS.

How can you possibly jack up transer rates that much using the off chip crystal clock? If you attempted to do that on the other side fo the I/O, what would that do to the input reference signal that is being multiplied on chip? You would have to deal with it somehow. But you could just as easily let the perhipehrial device's clock control the I/O and send the data to on chip registers and let CPU read the registers at is own frequency. Just as the 336 intended. And the rate of data transfer could even be a spread rate within a frequency range. It doesn't have to be fixed or in sync with anything.

This is only my opinion.

Opty