I have seen real products in applications with 8051's with as few as 128 bytes code and just a few bytes RAM. On the other hand I have seen an implementation of an 8051 program that was implemented with external bank switched EPROM and RAM. There was 512K bytes EPROM and 128K bytes of RAM.

I suggest that it is a near impossible question you ask.

On the other hand with the direction today of using on-board ISP supported FLASH the best judgement these days is it say biggest program goes to size of onboard memory resources in almost all cases. Plus if you have need for a larger program than that then you are most likely writing it in C and there are far better choices (and many many choices at that) for building systems with different microprocesors than 851 types.

I would not try to build a board that anticipates a solution for "all of what I will ever need". Goodness the first PCs had 64K of DRAM and I heard many times people that said "Why would anybody ever buy the 256K option?". And today we are fast approaching the time when a PC may routinely contain 1 or 2 GByte is RAM.

Michael Karas