Doh! My PLLs lose lock. Crosstalk?

I thought I would update on this one.

We re-laid the board. We put in filtering for the PLL pins. We checked the data and clock timing again. We cleaned everything up and.. it made no real difference. All my problems still felt like some sort of crosstalk inside the device. The more output activity, the less reliable the processing.

I fell across the answer by accident. We drive a 28 bit bus from one side of the chip at 40MHz, so that's a lot of output pins changing at the same time.

So.. I changed the current drive strength on all the outputs (except outgoing clocks and strobes) from 24mA which was the default, to 4mA.

This seems to have fixed it. At last. After three months...

:-)

Pete