Agnus is replaced with Super Agnus (8375) which allows a total of 2 MB chip RAM
an adaptor board plugs into the Gary socket
allows the use of trapdoor memory expansions larger than 512 kB, but needs another Gary adaptor in this case
three variants:
compact one for use in A2000 / A500
two bigger low-profile ones, which allow the use of internal A500 processor cards - these two differ only in their Agnus connector, as some A500 motherboard revisions have their Agnus socket rotated by 90°