The Disk System has a diagnostic test programmed into it. When starting up a Famicom connected to a Disk System, press and hold Start and Select. It will check the functionality of the RAM adaptor. If your RAM is ok, it'll read "PRAM CRAM OK." That's RAM for program storage (32k) and RAM for character storage (8k).

The RAM functionality test will look like this.

To find out if your Disk System is a version 1 or version 2, press and hold Start and Select, but before the RAM adaptor check screen appears, hit Right on the D-pad and the A button. If the screen reads "Dev. No. 2," you've got a version 2 Disk System; otherwise, you've got a version 1 Disk System.

The Disk System version test will look like this for a version 2 FDS.

The differences between the two version is minimal. If you've got a "Dev 2" version Disk System, it means your Disk System has slightly improved copy protection.

The version can also be determined by checking inside your Disk System. Take off the cover and ensure that the yellow eject button is pushed in. Now peer into the hole centered behind the drive head and locate the chip underneath.

The chip can be seen through the circled hole.

The Disk System's chip will either read "FD7201P" or "FD3206P". If you've got a 7201, then your disk system has little copyright protection and you can more easily use that FDS for rewriting disks. A 7201 Disk System is the earlier version of the Disk System.

The FD7201P chip.

Some have suggested that the easiest way to tell if you Disk System is a 7201 is to look at the color of the label on the bottom of the Disk System's outer casing. That label came in both pink and white. But 7201s have shown to come in Disk Systems with both pink and white labels.