That's only for one of the many optimisations he did, making use of different sections of memory to improve throughput. Many (all?) of the other ones don't incr

That's only for one of the many optimisations he did, making use of different sections of memory to improve throughput. Many (all?) of the other ones don't increase the memory requirements. Quite a few (such as re-rolling unrolled loops) should decrease code size (though that won't improve memory use on a ROM cartridge based system) improving cache efficiency.