The long-displacement facility wasn't in the first z/Architecture machine, but it followed soon thereafter. The first implementation was done in firmware — primarily to allow IBM internal testing of new software. It was implemented in hardware in any z/Architecture machine shipped after June 2003.
The presence of the facility is indicated facility indication bit 18 (facility installed) and bit 19 (facility installed in hardware) as stored by the STFL and STFLE instructions. (z/OS programmers take note: z/OS stores facility indications beginning at V=R location 200 (C8 hex), so you don't have to issue these instructions yourself.) Descriptions of newer facilities added to the architecture can be found in Chapter 1 of the PoO. Additional information as to the operation of the long-displacement facility can be found in the discussion of operand-address generation in Chapter 5, programming note 5 on p. 7-9, and elsewhere.
