The effective virtual address of a word was 17 bits.

A wide variety of possible addressing modes, used to specify the effective address of an operand, exist.

Indirect memory instruction - The effective address is being read from the memory.

The effective address for an absolute instruction address is the address parameter itself with no modifications.

The effective address for a Register indirect instruction is the address in the specified register.

After determining the effective address, the value in the base register is incremented by the size of the data item that is to be accessed.

Before determining the effective address, the value in the base register is decremented by the size of the data item which is to be accessed.

Typically the effective address is in bytes, so the block offset length is bits.

Instruction execution begins by calculating the effective address.

The resulting effective address can be used by the instruction either to fetch memory contents, or simply as a constant.