joe, you dont seem to recognize the difference between ram and flash. by my calculation only .05% of cpu time to refresh and 256kbyte not 4kbyte. using mega on that same simm would give 256kbyte. i have i huge box of those am tempted to give that a try.
WARNING: using this kind of RAM will put your Arduino CPU to refresh the SIMM RAM data most of the time. It means that your sketches (programs) could run slow. Also, we need to use most of the Arduino pins to be soldered with SIMM RAM pins so there will be just few available extra pins for your project.
SIMM RAM has 12 bit address for rows and columns. Max RAM size here is 16MB. We are using just 6 pins for rows and columns, so we are limited to 4KB of RAM space.Addresses space will be of 64rows x 64columns = 4096 addresses 1 byte each = 4KB of space.
If you need to use more RAM you can solder the 3 analog pins remaining to simm ram module pins A6, A7 and A8. It will give you 256 KB of RAM space.