Socket AM4 is a PGA microprocessor socket used by AMD's central processing units (CPUs) built on the Zen (including Zen+, Zen 2 and Zen 3) and Excavator microarchitectures. AM4 was launched in September 2016 and was designed to replace the sockets AM3+, FM2+ and FS1b as a single platform. It has 1331 pin slots and is the first from AMD to support DDR4 memory as well as achieve unified compatibility between high-end CPUs (previously using Socket AM3+) and AMD's lower-end APUs (on various other sockets). In 2017, AMD made a commitment to using the AM4 platform with socket 1331 until 2020.