There were no LOAD or STORE instructions. Instead there were "address" registers (18 bits wide), matched to each "operand" (60 bit data) register.
When you updated an address register, that memory address was automatically read into the correspond operand register. Except for the last couple address registers - updating them performed a write from the corresponding operand into memory.
By our current way of thinking, it seems arse about. But it worked well when you understood it, and apparently improved concurrency. Loads and stores became sort-of transparent. (Remembering that memory was as fast, sometimes faster than the CPU, so a few instructions saved was worth the occasional unnecessary load.)
See "Design of a Computer, The Control Data 6600" by J E Thornton.