I am designing new 8051 derivatives. I am using a stacked-die approach to put large amounts of flash in with the 8051. The smallest flash die I can get is 512 K-bytes, but I can get a 2 M-byte die for a modest increase in cost. Most of my chips are replacements for existing 8051-derivitives that have been discontinued, so I do not need the extra flash in these applications. On the other hand, the engineer in me can't stand the idea of just throwing the excess flash away, so I added bank switching to provide access to the full flash memory.

Since most existing applications are <64K, is there really a need to make an effort to provide the extra flash? If it is there in a -668 type processor, would anyone use it?

Is there any reason to try to push the limit to 2M-bytes, or beyond? I suspect that applications requiring that much code may also require a higher performance processor.

And, would the presence of an extra SRF register (in an unused address) for bank switching create problems be likely to create problems with existing code?

I would appreciate hearing thoughts on the subject.