It’s really easy to get confused when building your own rig for the first time, especially if you’re not quite familiar with various chipsets, CPUs, and CPU sockets. The CPU socket you have available on your motherboard is what determines which CPUs can physically fit inside your motherboard. AMD and Intel CPUs have different CPU sockets for different generations of CPUs and, if you want to own a certain CPU, you have to own a motherboard based on the same chipset, which will, in turn, have a specific CPU socket installed.
AM4 is AMD’s main CPU socket since February 2017, when the first 300-series chipsets were released with AM4 onboard. AMD has decided to stick with AM4 for a long time now, in contrast to Intel which pretty much releases a new CPU socket for each new generation of CPUs. AMD has received praise for that move but things aren’t as simple as that.
When a new CPU socket is released, it automatically renders all previous motherboards useless for the new generation of CPUs. AM4 is a long-term runner but not all motherboards with AM4 onboard can run any AM4 CPU. We’ll get to that later!
AM4 socket supports AMD CPUs built on the Zen and Excavator microarchitectures. In terms of Zen, it includes all current generations (Zen, Zen+, and Zen 2) and the future Zen 3 microarchitecture which is yet to be released. When it comes to CPUs, this covers Ryzen 1000, 2000, 2000, and (future) 4000 series. The Excavator microarchitecture is oriented towards APUs (Accelerated Processing Units) where the CPU and the GPU are integrated in the same package.
AM4 was launched in September 2016 to replace its numerous predecessors, including AM3+, FM2+, and FS1b, and provide a single socket to advance AMD’s impact on the desktop platform. It’s safe to say that it was the introduction of AM4 in 2016 that really made an impact and introduced AMD as a serious contender to Intel on the desktop CPU scene. The AM4 socket was deployed in the first generation of Ryzen CPUs in February 2017 and AMD has promised its customers that they will stick with AM4 until 2020. Well, it seems that they might prolong their use of AM4 as they confirmed that the future Zen 3 architecture will also be based on the AM4 socket.
AM4 has 1331 pins for the CPU to use. It’s the first AMD socket to support DDR4 RAM and to support both PCIe 3.0 and 4.0. You can install up to 4 sticks of DDR4 SDRAM in a dual-channel setup. Its size is the same as in previous sockets, being a 40 mm square.
Even though the size of the socket hasn’t changed, the dimensions of the heatsink for AM4 have changed when compared to previous sockets heatsinks. AM4’s heatsinks dimensions stand at 54×90 mm whereas its predecessors had a 48×96 mm heatsink. However, some older heatsinks could be reused. Some motherboard/cooler manufacturers offered various reusability solutions such as providing heatsink brackets or including heatsink mounting ports in both dimensions.
List of AM4 CPUs
Differences Between AM4 and Its Predecessors
As we’ve already mentioned, AM4 was introduced to unify AMD’s CPU sockets into a single one that will provide a platform to build and improve on. The heatsink dimensions were changed and many users feared whether their current cooling solutions would work with the CPU socket. In some cases, it was possible but many users had to buy new coolers if they wanted to switch to a new AMD CPU that used the AM4 socket.
The main difference between these sockets is CPU compatibility. If you want to see what AMD for desktop is all about, you’d have to go with an AMD Ryzen CPU. However, AMD Ryzen CPUs are all based on the AM4 socket and this doesn’t look like going away any time soon. It’s difficult to draw comparisons with all three of its predecessors but one thing is for certain: they need to be put in the past no matter if you are a gaming enthusiast or just someone who wants a fast computer for various applications.
AM4 Chipsets and CPU Compatibility
There are currently three generations of AMD chipsets released that feature the AM4 socket and they are usually released with two chipsets per generation: a “B” chipset for mainstream usage (stands for Basic and an “X” chipset for users who want extreme performance.
The first generation has introduced 300-series chipsets: A320, B350, and X370. Their connectivity options included the use of the PCIe 2.0 standard paired with SATA ports and a combination of USB 3.2 Gen 2, USB 3.2 Gen 1, and USB 2.0 ports. B350 and X470 also supported CrossFire and CPU overclocking. They support the Zen and Zen+ microarchitectures or Ryzen 1000 and 2000 CPUs and certain motherboards even support Zen 2 architecture (Ryzen 3000) with an optional BIOS update.
The 400-series chipsets, the B450 and X470, are currently the most popular choice among AMD users and for a good reason: they support everything from Zen+ to the future Zen 3 generation. Unfortunately, they are still using the PCIe 2.0 lanes but the overall connectivity is great, with plenty of USB 3.2 Gen 2, USB 3.2 Gen 1, and USB 2.0 ports.
Finally, we have the 500-series chipsets with X570, released in July 2019, and B550 which is yet to be released on June 16, 2020. These chipsets are the only ones that were built with Zen 3 and Ryzen 4000 CPUs in mind so make sure you keep that in mind when shopping for a new motherboard + CPU combo. X570 has switched to PCIe 4.0 for peripheral communication whereas B550 will use PCIe 3.0 lanes. X570 has also increased its required TDP from 4.8 W to 11 W. This is also the first generation of chipsets that doesn’t support all Zen microarchitectures as it has dropped the support for the Zen architecture and hence the Ryzen 1000 series CPUs.
Is AM4 the “One Socket to Rule Them All”?
AMD’s decision to stick with AM4 until (and throughout, it seems) 2020 was met with praise as users have expected that all motherboards with the AM4 socket will be able to run all AM4 CPUs. This would make motherboards a better and a more long-term purchase than motherboards for Intel CPUs, considering how often Intel decides to switch CPU sockets.
However, AMD didn’t have that in mind when they originally announced Ryzen 4000 CPUs as they were only meant to run on 500-series chipsets (X570 and B550). It wasn’t until they were met with community backlash that they changed their mind and decided to send motherboard manufacturers code that would enable them to deploy BIOS updates to enable the support for Ryzen 4000 CPUs.
The original reason why AMD has decided to drop the support is the size of BIOS chips. Most motherboards come with a 16 MB BIOS chip because the first AM4 CPUs could only address this memory size. Each new architecture (Zen, Zen+, Zen 2, Zen 3…) has its AGESA code that needs to be inserted into the motherboard’s BIOS if you want it to support the CPUs based on that microarchitecture.
That is why AMD has decided to draw the line and announce that 400-series motherboards will only support architectures up to Zen 2: because there was no space in BIOS. Fast forward to May 19, 2020, when AMD has announced they will provide support for Zen 3 on 400-series chipsets… how did they manage to find that extra space? Did they lie to us?
Well, not exactly. As AMD has announced on Reddit, they will provide the code needed to support Zen 3 to motherboard manufacturers but the BIOS updates they’ll provide will break your motherboard’s compatibility with anything older then Ryzen 4000. In short, once you go Ryzen 4000, you never go back! These updates will be optional but you won’t be able to flash an older version of BIOS after that. Also, these updates won’t be available from day one and it’s safe to say 400-series motherboard owners will have their fair share of waiting and worrying whether they’ll motherboard will receive the BIOS update and whether everything will work out in the end.
Now you know how AMD managed to resolve the problem: the download and the flashing of the optional BIOS update would probably overwrite the data you need to flash Zen+ and Zen 2 CPU. Still, it’s nice of AMD to think of a way to keep their customers happy, despite the fact they want to grow and evolve as a company and provide new, modern CPU solutions that also require a modern motherboard and chipset. This might prove that AMD may be great enough to challenge Intel but not too big to listen to its customers.
What Comes After AM4?
“AM5, of course!”, one might say. Well, speculation is all that is available at the moment. AMD hasn’t released anything specific and it’s probably because they’re still not sure themselves. This is a big decision for the company and there are probably dozens of factors that might influence their decision.
When it comes to customers, they are split between customers who are excited to see chipsets with faster connectivity, better CPUs, and new technologies that improve their gaming experience. However, such customers aren’t on a strict budget and they have no problems upgrading their setup once a year.
Other customers are usually on a budget and they would like for their motherboard to be able to run at least two or three generations of CPUs. For example, if AMD decided to drop AM4 when developing the Zen 4 microarchitecture (and probably new Ryzen 5000 CPUs), customers who have purchased an X570 or a B550 motherboard would have all the right in the world to be furious at AMD since they’ve purchased a motherboard that has only lasted a generation!
GamersNexus has claimed in a news flash that an insider from AMD claims that Zen 4 is set for 2022 and it includes USB 4 support, DDR5, and full PCIe 4.0 integration. These changes are drastic and they might require technology changes that result in a different required CPU pin count or layout, which calls for a new socket, as AMD has explained in their Q&A. The future is definitely bright and keeping up with technology has never been easy or cheap.