Oh Yes. Now your original query falls into place!

I think you ARE referring to a Flash variety with a generic 8051 name. All such confusion can be avoided by giving specific model numbers of the MCU that you are using.

You get Flash memories for code upto 64K on a single MCU. DO you need more memory than this ? In which case only you will need an external EPROM that is UV erasable ( pain in the neck ) or Flash type ( joy to work with ).

Apart from above all, you will need to resort to code-banking to handle the code that is more than 64K and that is the REAL pain in my honest opinion.

Raghu