A Single In-line Memory Module (SIMM) is a type of memory module containing Random Access Memory (RAM) which was used in computers from the early 1980s to the late 1990s (think 386, 486, Macintoshs, ...
When it comes to performance, there's a world of difference between the Raspberry Pi and Arduino. The former, after all, is technically a fully functional computer that can run games, word processors, ...