Wikipedia
ISEPIC
The ISEPIC from Starpoint Software in USA is an extension cartridge which was introduced in June 1985 for the Commodore 64. It offers the capability to memory dump software regardless of the implementation scheme or storage medium. The resulting snapshot can be tested before saving.
Snapshots require ISEPIC to run. The cartridge vanished at the end of 1985 but still sold 20,000 units around the world, mostly by word of mouth at local computer clubs and niche magazines.
A major factor is the 2 kB RAM that could be reprogrammed And thus allowed the user to change its functionality. The 2 kB RAM is memory banked into a 256-byte page at 0xDF00 – 0xDFFF.