The Fujitsu chip is the maker of the EPROM device not the map, in the same way Intel make the processor for your PC.
The Subaru JECS ECU was designed to have the spare slot for Group'N' rally regulations. These were, the car had to run the standard manufacturers ECU.
It didn't say anything about being able to run a different map, which Subaru overcame by fitting the Fujitsu 27C1024 EPROM device in a spare location on the eCU motherboard.
The Polar chip is a Fujitsu 27C1024 blank device which is then programmed with my map.
Interested to here how it compares to the other 2
