With the CR2032 backup battery installed I did some experiments with the data retention and how the PX-4 handles RAM Disk disconnects and reconnects. The Epson RAM Disk manual states that a disconnected RAM Disk does not retain its information. With some simple experiments it shows the fully static replica is more reliable. Two scenario's are tested:

- Disconnect and reconnect with the PX-4 switched off.

Here the PX-4 didn't even notices the disconnect.

- Disconnect the RAM Disk, start the PX-4 and initialize the Internal RAM Disk. Then switch it off and reconnect the RAM Disk.

Here the PX-4 re-initializes and asks if the RAM Disk should be formatted. When answered No, the old RAM Disk is accepted and it works as expected. Internally the RAM Disk has check sums for each section/page and if these match the contents, the contents is assumed valid. This is BTW another test for the proper operation of the auto-increment feature in the GAL.

Allowing disconnects of the RAM Disk is an useful feature as the connection between PX-4 and the RAM Disk in its current form isn't as robust as the original.