I never understood why you guys mentioned non-REV cards as REV 0 cards, as i think these are the latest more standardized high level of production models.
Maybe at the point they were producing cards with V2.02 DSP they either decided not to sell upgrades anymore or no one ever asked for them. Because even if someone had, it would be very simple to Creative to change the PAL code to be suitable for DSP 2.02 boards. Something changed with the DSP revisions, because i bet PCB's were exactly the same.
maybe 2.02 DSP had that problem and that's why later revisions used 2.01...
makes no sense to me as these companies redesign their chips for several important reasons like manufacturing costs, solve bugs, enable/disable features etc...
It could be that at the same time the move was intentionally to prevent older upgrade kits to work on boards with newer DSP. Probably if this is true maybe Creative was already manufacturing Sound Blaster Pro's, when they make the DSP change for the Sound Blaster 2.0. But then why manufacture the cards with the upgrade sockets?
Makes more sense to me that the changes on the DSP required a reprogrammed PAL, and at this time no one was buying upgrades or to few people bought them while at the same time the Sound Blaster Pro was already available.