AM4 was launched in September 2016 and was designed to replace the socketsAM3+,FM2+ andFS1b as a single platform. It has 1331pin slots and is the first from AMD to supportDDR4 memory as well as achieve unified compatibility betweenhigh-end CPUs (previously usingSocket AM3+) and AMD's lower-endAPUs (on various other sockets).[3][4] In 2017, AMD made a commitment to using the AM4 platform with socket 1331 until 2020.[5][6][7]AM5 succeeded the AM4 platform in late 2022 with the introduction of theRyzen 7000 series, however, AMD has continued to release new CPUs for AM4 even after the release of AM5.[8][9][10][11]
The AM4 socket specifies the four 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.[14][15] Some cooler manufacturers, however, are reported to be offering brackets allowing previously manufactured coolers to work with AM4,[16] while other coolers will be redesigned.[17][18] Alternatively, some motherboard makers are including bothAM3 and AM4 cooler mounting holes, allowing previous generation coolers to be used.[19] AM4 coolers that use a two-pronged bracket approach (such as the AMD Wraith Prism) to mount the cooler will work with AM4 and all the way back to Socket 754/939.
Socket AM4 is currently a base for 8chipset models. While the processors for this socket have been designed assystems in a package (SiP), with the traditionalnorthbridge andsouthbridge on board the processor, the motherboard chipset will increase the number ofPCI Express lanes and other connectivity options. These connectivity options include:NVMe,SATA, andUSB 3.2 Gen 2.[2][18][20] There also exists chipset-less variations of A320 and X370, called A300 and X300 respectively, that rely solely on the I/O die integrated into the CPU; these platforms are designed solely forsmall form factor (SFF) systems where there is a possibility that there is not enough space on the board to fit an actual chipset; these 'chipsets' are also solely available for OEM use only and are not available for purchase with SFF boards.[2][18][21]
In 2020, AMD faced some criticism when it was announced on May 7 that itsZen 3-based Ryzen 5000 microprocessors would only be compatible with newer 500-series chipset AM4 motherboards.[41][42][43] This was explained as motherboard BIOS's sizes not being large enough to support the full range of AM4 socket processors.[41][43] This had upset some of the user base as, described byAnandTech, they "...had assumed that this meant any AM4 platform based motherboard would be able to accept all processor made from 2016 to 2020, including the new Zen 3...".[43] After the announcement some motherboard manufacturers announced they were planning to add in support for Zen 3 processors via BIOS updates.[41][44]
On 19 May 2020, however, AMD changed its position and stated that Zen 3 would be coming to selected older X470 and B450 motherboards via a BIOS update.[45] 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.[45][46][43]
On 12 November 2021, according toTechPowerUp, ASUS and Gigabyte were the few vendors that allowed Ryzen 5000 on A320 motherboard, and according toTom's Hardware, it was done by removing support for AMD's 7th Generation A-series and Athlon X4 series (Bristol Ridge) processors.[47][48] AMD later officially expanded Ryzen 5000 support to 300-series motherboards in March 2022.[49][50]
