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The AM4 is a CPU socket used by AMD for the company’s Ryzen CPU lineup. The AM4 features the pin grid array design and has been used for all Ryzen processors ever since the first-gen Ryzen lineup debuted in 2017. The socket itself debuted in September 2016. You can find the AM4 socket on eight chipsets, starting with the ancient B350 and X370, up to the relatively recent B550. If you want to find out more about CPU sockets, and processors in general, feel free to visit Levvvel’s CPU section. It’s pretty informative.
Being a PGA design instead of LGA, the AM4 socket features 1331 pin slots instead of pins. Pins can be found on the CPU. Some of the most critical features that debuted during the AM4 era include DDR4, PCIe 4.0, and AMD’s Infinity Fabric. While there are more and more rumors about AM4’s successor, chances are AMD will utilize the socket one last time, for Zen 3D CPUs. Below you can find the full AM4 CPU list as well as comparisons with other AMD sockets, AM4 hardware specs, and the list of chipsets featuring the socket.
AM4 CPU list
AM4 Hardware Specs
AMD introduced the AM4 socket back in 2017. The company launched the socket as a one-for-all CPU socket, meant to replace every other consumer-grade AMD CPU socket of the time (AM3+, FM2+, etc.). When it comes to HEDT (high-end desktop) and server processors, AMD decided to use different, LGA-based sockets, such as the TR4, sTRX4, and SP3. The AM4 supports up to four sticks of DDR4 memory in dual-channel configuration. As for the maximum memory speed, newer CPUs and boards officially support DDR4 up to 3200 MT/s but in reality, you can use faster memory without issues.
The AM4 socket features the Pin Grid Array (PGA) design in which the protruding pins used for contact between the socket and the CPU are on the CPU backside. The socket houses the holes for the said pins – 1331 in total – which is entirely different from the PGA design used by Intel. PGA design isn’t slower or anything, but users have a higher chance of messing things up while installing the CPU because the protruding pins can bend quite easily. That’s despite the AM4 being a ZIF, or zero insertion force, socket. On the other hand, the CPU installation procedure with an LGA socket is a fairly bit simpler and less prone to pin bending.
The AM4 socket measures 40mm x 40mm, and uses a different cooling solution hole pattern than its predecessor, the AM3+. Instead of the 54mm x 90mm hole pattern seen on the AM3+ AM4 uses a 48mm x 96mm hole pattern. This is why all AM4-based motherboards require mounting brackets that are specifically compatible with the AM4 platform. Of course, most current cooling solutions work great with Ryzen processors.
The most important new technology that debuted alongside the AM4 is Infinity Fabric; a high-speed “system interconnect architecture” used for communication between an AMD Ryzen CPU or AMD GPU and the rest of the system. Other new technologies that first debuted on AM4-compatible chipsets and CPUs include DDR4 memory and PCIe 4.0 interface. It’s now all but certain that the AM4 won’t see the introduction of DDR5 memory and PCIe 5.0 interface. AMD reserved these two for the AM5 socket.
AM4 vs AM3+
The AM3+ is a direct predecessor of the AM4. It uses the same PGA design and includes 942 pinholes found on the socket itself. Despite the socket having 942 pin holes, CPUs compatible with the AM3+ only have 940 pins on their backside. AMD released the socket in 2011. The company designed the AM3+ for the CPUs based on the, now ill-fated, Bulldozer microarchitecture. The AM3+ is mechanically compatible with the older AM3 CPU socket.
However, the AM4 and AM3+ aren’t compatible, mechanically or electrically, even though they have the exact dimensions of 40mm square. The AM4 introduced a new hole pattern for cooling solutions despite the two sockets sharing physical dimensions. Also, it’s interesting that, despite being the same size and the AM4 having a large hole in the middle, AMD managed to squeeze 389 extra pin holes on the newer socket.
AM4 vs AM5
We don’t know much about the upcoming AM5 socket, which AMD should use for the Zen 4 processors. What’s almost certain is that, with the AM5, AMD will finally switch to the LGA socket design for its consumer-based CPUs. The company already has experience using the LGA-based socket for its Threadripper and Epyc series of processors. Rumors claim the upcoming socket will come with 1718 contacts or pins. This, if correct, will be a massive, 29.1 percent increase in pins/holes compared to the AM4 socket.
The AM5 will also almost certainly launch with DDR5 and PCIe 5.0 support. This info isn’t 100 percent confirmed, but given that Intel launched its LGA 1700 socket and Z690 motherboards with support for the same technologies, we reckon AMD will do the same with the AM5 and corresponding chipsets.
CPUs compatible with AM4
The first generation of AM4 motherboards supported the last generation of Excavator CPUs – i.e., A6-9550 – and the first-gen Ryzen processors. Over the years, the AM4 continued to be the only CPU socket used for consumer-grade AMD CPUs. Today, the socket is compatible with all four generations of Ryzen CPUs – Zen, Zen+, Zen 2, and Zen 3. And, by the looks of it, the socket could also be compatible with the upcoming Zen 3D, a Zen 3 refresh that includes 3D V-cache technology.
With that said, not all AM4-based chipsets are compatible with all AM4-based CPUs. The first generation of chipsets (A320, B350, and X370) supports Excavator and Ryzen CPUs up to Ryzen 3000 series, depending on the BIOS version. The second generation of Ryzen-chipsets (B450, X470) has support for every generation of Zen CPUs. Again, with an appropriate BIOS version. Finally, the latest chipsets – A520, B550, X570 – support Zen 2 and Zen 3 CPUs. In the future, they might also be compatible with the Zen 3D CPU lineup.
As for the technologies and standards found on CPUs compatible with the AM4, there are many of them. The most important one is Infinity Fabric, which allowed the chiplet-based design each Ryzen CPU is based on. Next, the AM4 and compatible CPUs only support DDR4 memory. The first generation of CPUs and motherboards had a ton of teething pains, but today, Ryzen CPUs work great with high-speed DDR4 memory. You can equip AM4-based boards with up to four sticks of DDR4 RAM. And while the maximum supported speed is DDR4 3200 MT/s, all newer Ryzen CPUs and motherboards have zero issues with DDR4 3600 memory and faster.
As for the PCIe interface, the AM4-compatible chipsets work with CPUs compatible with PCIe 3.0 and 4.0 standards. The socket was also the first AMD socket to see M.2 slots and support for the NVMe storage standard. AMD pushed SATA Express and its proprietary StoreMI technology, but, over time, both storage standards made way for the good old SATA III and NVMe. Finally, most AM4-compatible chipsets support overclocking, with X-series chipsets also supporting multi-GPU setups.
Chipsets featuring AM4 socket
There are eight chipsets housing the AM4 socket. They’re divided into three categories: the A series includes entry-level chipsets with a limited number of features. Next, we have the B-series chipsets, mid-range options that come with a wide array of features, overclocking support, and are the best choice for most users. The X-series of chipsets comes with the most PCIe lanes, high-speed USB ports, and M.2 slots for NVMe SSDs. X570 boards are the best choice for power users needing multiple PCIe 4.0 M.2 slots. However, budget X570 boards could also be a solid choice for gaming setups. Unlike what they did with their earlier sockets, AMD uses the AM4 for every consumer-based CPU and APU; from low-end options to flagship models. Here’s the list of chipsets that house the AM4 socket:
- A320
- B350
- X370
- B450
- X470
- A520
- B550
- X570
Explaining threads, base & boost clock, and TDP
CPU threads and hyperthreading – Every CPU has a certain number of physical cores. If a CPU supports hyperthreading or simultaneous multithreading, as AMD calls the technology, each physical core can be divided into two virtual ones. Each of the virtual cores can then process a single task or thread. In other words, each physical core then, technically, is working on multiple tasks or threads simultaneously. Two virtual threads will always be weaker than two physical threads, though.
And while hyperthreading improves CPU performance, some fringe cases see a lower performance with hyperthreading than without it. Certain games are a pretty good example. While some games work slower with hyperthreading turned on, others run faster. The difference isn’t big in most cases, but it’s definitely there.
Base & Boost clocks – On Ryzen CPUs, the base clock is the processor’s frequency while idle. And even when performing certain undemanding tasks (writing in Microsoft Word, browsing the web, etc.), most cores will work at the base clock since only one or two cores are under load during light workloads.
The maximum boost clock on Ryzen CPUs is the highest frequency a single physical CPU core can reach when under load. For instance, the Ryzen 5 5600X has a base clock of 3.7 GHz and a max boost clock of up to 4.6 GHz. This “up to” is there for scenarios when a user pairs the CPU with an inappropriate thermal solution or if the board has a weak VRM section, both of which can affect the CPU and prevent it from reaching the advertised frequencies.
TDP (Thermal Design Power) – TDP or thermal design power represents the maximum power consumption a CPU can reach with default clocks & settings. And while Intel has all but abandoned classic TDP labels, Ryzen processors have pretty accurate TDP numbers. For instance, the 5600X will reach around 65W under max load, precisely its TDP value. However, official TDP values go off the boat when you overclock a Ryzen CPU or turn on PBO (precision boost overclock, basically an auto OC option found on most AM4-equipped motherboards). The advertised TDP is very accurate to real numbers at stock settings, at least when we’re talking about Ryzen CPUs.
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