AMD confirmed that hitting 2,000 MHz on the Infinity Fabric clock on Ryzen 5000 CPUs may not be as easy as expected. If you were looking at 4000MHz DDR4, you probably would rather wait for BIOS updates.
In fact, PC Gamer mentions that even using a Corsair Vengeance RGB Pro DDR4-4000MHz RAM alongside the Ryzen 9 5900X when running the FCLK above 1800 MHz, it resulted in a failed attempt every time it was tested.
AMD’s response was as follows: “We are working on additional optimizations for the 1900-2000MHz fabric clocks in our next version of AGESA. AMD cannot guarantee that any sample (including the 5900X) can achieve these speeds. While some current Ryzen 5000 samples can reach 1900+ fabric speeds, we are confident that even more users will be able to achieve these speeds with upcoming optimizations. If you recall on the 3000 series, many, but not all, users were able to reach a fabric speed of 1900. We think it will be a similar situation with 5000 and 2000MHz series processors.”
But why is this so important?
The main reason this is important is that a 1: 1 ratio is sought between the memory clock and the Infinity Fabric for optimal performance. Running a memory at 4,000MHz (which is actually clocked at 2,000MHz) in conjunction with a FCLK of 1,800MHz will cause the buses to not be as well synchronized as they could be.
It’s not the first time we’ve seen this in the FCLK as XT chips can potentially run at 1,900 MHz. Some users managed to get the Infinity Fabric to run at 1,900 MHz and memory at 3,800 MHz, although the real difference this made in the games are not very clear. Also, not all processor, motherboard, and memory combinations proved successful, which is probably why AMD didn’t make much of a buzz about this update.