== 170 address registers == 

 Seven of the A registers were tied to their corresponding X register. Storing an address into register A1, for example, caused the contents of the central memory word referenced by that address to be fetched into register X1. Likewise, storing an address into register A7 caused the contents of register X7 to be stored to the central memory location referenced by A7. 

 Storing into A1 fetches into X1, but storing into A7 stores from X7?  Some of the seven fetch and some store?  If someone would fix or clarify…