It looks like an 8 megabyte RAM expansion with floating point unit and real-time clock. When it's plugged in the PCMCIA slot on the left side of the computer doesn't work due to the limited addressing of the 68ec020 main processor.
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It also means that it will be difficult to install a network adapter since that typically plugs into the PCMCIA slot and that the computer is still running at the original 14 MHz clock speed.
