Socket AM4


Socket AM4 is a microprocessor socket used by AMD's central processing units built on the Zen 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 and AMD's lower-end APUs. In 2017 AMD made a commitment to using the AM4 platform with socket 1331 until 2020.

Features

The AM4 socket specifies the 4 holes for fastening the heatsink to the motherboard to be placed in the corners of a rectangle with a lateral length of 54×90 mm. Previous sockets have 48×96 mm.
Some heat sinks for older sockets are not compatible. However, some cooler manufacturers are reported to be offering brackets allowing previously manufactured coolers to work with AM4, while other coolers will be redesigned. Alternatively, some motherboard makers are including both AM3 and AM4 cooler mounting holes, allowing previous generation coolers to be used.

Chipsets

Socket AM4 is currently a base for 6 chipset models. While the processors for this socket have been designed as systems on a chip, with the traditional northbridge and southbridge on board the processor, the motherboard chipset will increase the number of PCI Express lanes and other connectivity options. These connectivity options include: NVMe, SATA, and USB 3.2 Gen 2.

Criticism

In 2020 AMD faced some criticism when it was announced on 7 May that the Zen 3/Ryzen 4000 microprocessors would only be compatible with newer 500-series AM4 motherboards. This was explained as motherboard BIOS's sizes not being large enough to support the full range of AM4 socket processors. This had upset some of the user base as, described by Anandtech, they "...had assumed that this meant any AM4 platform based motherboard would be able to accept any processor made from 2016 to 2020, including the new Zen 3...". After the announcement some motherboard manufacturers announced they were planning to add in support for Zen 3 processors via BIOS updates.
However on 19 May 2020 AMD changed its position and stated that Zen 3 would be coming to selected older X470 and B450 motherboards via a BIOS update. This would be achieved by disabling support for some older AM4 processors in the BIOS ROM in order to allocate space to support the newer processors.