The PDI 256 provides up to 256KB of user memory with parity on a single expansion board for the IBM Personal Computer.
Memory is organized as 4-64KB memory banks, each bank can be set to any 64K boundary within the 1 MB address space.
Individual memory banks may also be deselected.
All address mappings are made by DIP switch settings for easy configuration.
All RAM chips are socketed to allow for easy memory add-on or replacement.
Memory refresh for PDI series memory boards coincides with the planar board’s refresh.
No wait-states are required for expansion memory accesses.

The board is currently set up to add 256KB of memory to a 256KB motherboard.