Socket AM4

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Socket AM4
Sockel AM4 6936.jpg
Chip form factorsFlip-chip
FSB protocolInfinity Fabric, PCI Express
Voltage range1.3V
ProcessorsRyzen: Athlon:
  • Raven Ridge
  • Picasso
A-Series, Athlon X4:
PredecessorAM3+, FM2+, AM1
SuccessorSocket AM5
Memory supportDDR4

This article is part of the CPU socket series

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.[1][2]

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).[3][4] In 2017, AMD made a commitment to using the AM4 platform with socket 1331 until 2020.[5][6][7]


The X370 chipset supports multiple graphics cards. But the number of available PCIe lanes depends on the CPU/APU.
  • Support for Zen (including Zen+, Zen 2 and Zen 3) based family of CPUs and APUs (Ryzen, Athlon), as well as for some A-Series APUs and Athlon X4 CPUs (Bristol Ridge based on the Excavator microarchitecture)
  • Supports PCIe 3.0[8] and 4.0[9]
  • Supports up to 4 modules of DDR4 SDRAM[8] in dual-channel configuration


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.[10][11] Some cooler manufacturers, however, are reported to be offering brackets allowing previously manufactured coolers to work with AM4,[12] while other coolers will be redesigned.[13][14] Alternatively, some motherboard makers are including both AM3 and AM4 cooler mounting holes, allowing previous generation coolers to be used.[15] 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 8 chipset models. While the processors for this socket have been designed as systems in a package (SiP), 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.[2][14][16] 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 for small 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][14][17]

Model Release date PCIe support[a] Multi-GPU USB support[b] Storage features Processor
TDP CPU support[18] Architecture
CrossFire SLI SATA ports RAID AMD StoreMI Excavator Zen Zen+ Zen 2 Zen 3
A320 February 2017[19] PCIe 2.0 ×4 No No 1, 2, 6 4 0,
No Limited to pre-Zen CPUs ~5 W[20] Yes Yes Yes Varies[c] Promontory
B350 February 2017[19] PCIe 2.0 ×6 Yes 2, 2, 6 Yes
X370 February 2017[19] PCIe 2.0 ×8 Yes 2, 6, 6 8
B450 March 2018[21] PCIe 2.0 ×6 No 2, 2, 6 4 Yes Yes,
with PBO
Varies[d] Yes Varies[d][22]
X470 March 2018[21] PCIe 2.0 ×8 Yes 2, 6, 6 8
A520 August 2020[23] PCIe 3.0 ×6 No No 1, 2, 6 4 No No Varies Varies Yes
B550[e] June 2020[24] PCIe 3.0 ×10[25] Yes Varies 2, 2, 6 6 Yes,
with PBO
X570 July 2019[26] PCIe 4.0 ×16 Yes 8, 0, 4 12 ~15 W[27][28] [f] Yes Bixby
AMD Pro 500 Not a real chipset, but a simple activator chip which signals the processor to use its own integrated IO die N/A Select CPU SKUs branded as Ryzen PRO N/A
Knoll Not a real chipset, but a simple activator chip which signals the processor to use its own integrated IO die [g] No Yes N/A
  1. ^ PCIe lanes provided by the chipset. The CPU provides other PCIe 3.0 or 4.0 lanes.
  2. ^ USB 3.2 Gen 2, USB 3.2 Gen 1, USB 2.0
  3. ^ BIOS update needed. Availability may depend on manufacturer.
  4. ^ a b Beta BIOS updates may be made available by motherboard manufacturers.
  5. ^ OEM-only variants B550A with and two more USB ports and two more PCIe lanes added; and Pro 560, and Pro 565 with overclock disabled, also exist.
  6. ^ 7W on passive cooling (termed X570s).
  7. ^ Two settings of Knoll activator exist: A300 platform, overclock disabled; and X300 platform, overclock enabled


In 2020, AMD faced some criticism when it was announced on 7 May that the Zen 3/Ryzen 5000 microprocessors would only be compatible with newer 500-series AM4 motherboards.[29][30][31] This was explained as motherboard BIOS's sizes not being large enough to support the full range of AM4 socket processors.[29][31] 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 all processor made from 2016 to 2020, including the new Zen 3...".[31] After the announcement some motherboard manufacturers announced they were planning to add in support for Zen 3 processors via BIOS updates.[29][32]

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.[33] 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.[33][34][31]

On 12 November 2021, according to TechPowerUp, ASUS and Gigabyte are the few vendors that allowed Ryzen 5000 on A320 motherboard and according to Tom's Hardware it was done by removing support for AMDs 7th Generation A-series and Athlon X4 series (Bristol Ridge) processors.[35][36]

See also[edit]



  1. ^ Tyson, Mark (5 September 2016). "7th Generation AMD A-Series desktop PC systems start to ship". Hexus. Retrieved 5 September 2016.
  2. ^ a b c Mah Ung, Gordon (5 September 2016). "AMD's new Bristol Ridge processor is faster and more power efficient". PC World. Retrieved 5 September 2016.
  3. ^ "AMD's 2016-2017 x86 Roadmap: Zen Is In, Skybridge Is Out". Retrieved 2015-06-19.
  4. ^ MujtabaHassan, Hassan (2015-05-07). "AMD Confirms x86 Zen Based Enthusiast FX CPUs and 7th Generation APUs in 2016 - Compatible With AM4 Socket". WCCFtech. Retrieved 2016-09-16.
  5. ^ Bright, Peter (2 March 2017). "AMD's moment of Zen: Finally, an architecture that can compete". Ars Technica. Retrieved 18 May 2020.
  6. ^ Leather, Antony (9 March 2018). "More AMD CPU Leaks Revealed: Ryzen 2nd Gen Details Plus AM4 And TR4 Socket Life Confirmed?". Forbes. Retrieved 18 May 2020.
  7. ^ "AMD reaffirms commitment to AM4 socket until 2020". 21 April 2018. Retrieved 19 May 2020.
  8. ^ a b Moammer, Khalid (16 September 2016). "AMD Zen CPU & AM4 Socket Pictured – PGA Design With 1331 Pins Confirmed". WCCFtech. Retrieved 2016-09-16.
  9. ^ "The Industry Leading AMD AM4 X570 Chipset". AMD Community. 2019-05-26. Retrieved 2019-06-10.
  10. ^ Peak, Sebastian (19 September 2016). "AMD's Upcoming Socket AM4 Pictured with 1331 Pins". PC Perspective. Retrieved 21 September 2016.
  11. ^ "Report: AMD Socket AM4 Compatible with Existing AM2/AM3 Coolers | PC Perspective".
  12. ^ Killian, Zak (25 January 2017). "CPU heatsink makers ready up Socket AM4 mounting kits". Tech Report. Retrieved 25 January 2017.
  13. ^ Chacos, Brad (4 January 2016). "AMD reveals an army of Ryzen PCs and AM4 motherboards". PC World. Retrieved 10 January 2017.
  14. ^ a b c Walrath, Josh (7 January 2016). "AMD Details AM4 Chipsets and Upcoming Motherboards". PC Perspective. Retrieved 10 January 2017.
  15. ^ Cutress, Ian (2 March 2017). "The AMD Zen and Ryzen 7 Review". Anandtech. Retrieved 2 March 2017.
  16. ^ Cutress, Ian (13 December 2016). "AMD Gives More Zen Details". Anandtech. Retrieved 13 December 2016.
  17. ^ "Socket AM4 Chipset". AMD.{{cite web}}: CS1 maint: url-status (link)
  18. ^ Hassan Mujtaba (2019-05-27). "AMD X570 Motherboard Roundup – Featuring X570 AORUS Xtreme, ASRock X570 Taichi, MSI MEG X570 GODLIKE, ASUS Crosshair VIII HERO & More". wccftech. Retrieved 2019-07-10. slide
  19. ^ a b c Khalid Moammer (2017-02-13). "AMD Ryzen X370 & B350 ASUS Motherboards Leaked – Launching February 24th". wccftech. Retrieved 2019-07-10.
  20. ^ Ian Cutress (2016-09-23). "The Two Main Chipsets: B350 and A320". AnandTech. Retrieved 2019-06-15.
  21. ^ a b Jacob Ridley (2018-01-05). "AMD's 12nm Ryzen 2 expected to launch in March alongside X470 and B450 chipsets". PCGamesN. Retrieved 2019-07-10.
  22. ^ "AMD Reverses Course, Will Enable Zen 3 and Ryzen 4000 Support on B450 and X470 Motherboards". Tom's Hardware. Retrieved 19 May 2020.
  23. ^ "ASRock Follows ASUS, Registers 12 AMD A520 Motherboards for Ryzen 4000 Chips". Hardwaretimes. 2020-06-06. Retrieved 2020-08-18.
  24. ^ "AMD Expands 3rd Gen AMD Ryzen™ Desktop Processor Family, Unleashing Powerful "Zen 2" Core For The Mainstream". AMD. 2020-04-21. Retrieved 2020-05-25.
  25. ^ "AMD Chipset Comparison: B550 Specs vs. X570, B450, X370, & Zen 3 Support (2020)". GamersNexus. Retrieved 8 October 2020.
  26. ^ CrimsonRayne (2018-12-01). "AMD X570 Launches at Computex & Supports PCIE 4.0 | Ryzen 3000 Series Launch Date Leaked?". redgamingtech. Retrieved 2019-07-10. the X570 platform is targeting a release of Computex 2019, which takes place between May 28th and June 1st.
  27. ^ Gavin Bonshor (2019-05-26). "AMD Reveals the X570 Chipset: PCIe 4.0 is Here". AnandTech. Retrieved 2020-08-19. One of the caveats to a more powerful chipset is that it draws around 11 W of power.
  28. ^ "AMD X570 Unofficial Platform Diagram Revealed, Chipset Puts out PCIe Gen 4". TechPowerUp. 2019-05-20. Retrieved 2020-08-19. The source also mentions the TDP of the AMD X570 chipset to be at least 15 Watts, a 3-fold increase over the X470 with its 5W TDP.
  29. ^ a b c Mujtaba, Hassan (7 May 2020). "AMD Ryzen 4000 'Zen 3' CPUs Compatible With X570 & B550 Chipset". Wccftech. Retrieved 18 May 2020.
  30. ^ Hallock, Robert (7 May 2020). "The Exciting Future of AMD Socket AM4 | Community". AMD. Retrieved 19 May 2020.
  31. ^ a b c d Cutress, Ian (19 May 2020). "AMD to Support Zen 3 and Ryzen 4000 CPUs on B450 and X470 Motherboards". Anandtech. Retrieved 19 May 2020.
  32. ^ Mujtaba, Hassan (16 April 2020). "AMD Zen 3 Ryzen 4000 'Vermeer' Desktop CPUs Will Be Compatible With Existing AM4 Boards". Wccftech. Retrieved 18 May 2020.
  33. ^ a b "r/Amd - The "Zen 3" Architecture is Coming to AMD X470 and B450". reddit. 19 May 2020. Retrieved 2020-05-19.
  34. ^ "AMD "decided to change course" with Zen 3 B450/X470 support". HEXUS. Nexus. 19 May 2020. Retrieved 19 May 2020.
  35. ^ AleksandarK Discuss. "ASUS and GIGABYTE Enable AMD Ryzen 5000 Series Processor Support on A320 Chipsets". TechPowerUp. Retrieved 2021-11-16.
  36. ^ Liu, Zhiye (2021-11-12). "Ryzen 5000 Support Finally Enabled On A320 Motherboards". Tom's Hardware. Retrieved 2021-11-16.