A few weeks ago we told you that the new AMD Ryzen 7000 processors would support DDR5 at 6 GHz in 1:1 mode, and that this would be the “optimal point” we could reach without the Infinity Fabric Clock at most. ( FCLK) switch to 1:2 mode. It wasn’t official information, so it wasn’t confirmed by AMD, but it had a lot of credibility and finally was supported by Robert Hallockdirector of technical marketing at AMD, albeit with some important nuances what will we see next

In a Q&A round, an AMD executive provided all the details we need to know to choose the best DDR5 RAM to accompany our Ryzen 7000, and we have two important keys on the table: must work at 6 GHz, a level that is defined as “optimal” in relation to price, stability, performance and availability by Hallock himself and will be better to use only two modules instead of fouralthough I’m aware that for aesthetic reasons there will be those who prefer to occupy the motherboard’s four DIMM slots.

We have already explained the issue of DDR5 RAM and Ryzen 7000 frequency. Early leaks suggested that if we ran the RAM at more than 6GHz, the FCLK would go from working in 1:1 mode to working in 1:2 mode, which will reduce the working frequency by half, and that the FCLK speed will be 3 GHz by default. This relationship between RAM speed and Ryzen 7000 FCLK seems to be wrong because the default FCLK configuration will be 1733 MHz, and not 3 GHz as was said.

So if we use memory DDR5 at 5200 MHzwill the Infinity Fabric Clock work 1733 MHzthe memory controller (UCLK) does this. 2,600 MHz and the memory clock (MCLK) will run at 2,600 MHz AMD emphasized that some samples would be able to reach 2000 MHz in FCLK, but that this was not a priority for AMD.

As for occupying only two DIMM slots, Hallock explained that this is better because it is the inherent nature of signal routing for DDR memoriesand that it is very difficult to route four slots while running at high speed because signal integrity becomes a “hit”. To better illustrate this question, we can only see the list of frequencies and occupied slots that AMD collects on its official website:

• 5200 MHz with one or two populated slots and one DIMM per channel.
• 3600 MHz with four occupied slots or two DIMMs per channel.

Robert Hallock pointed this out 1:1:1 mode is not so important anymoreand that the user will get the best results by leaving the FCLK in auto mode and adjusting the RAM and memory controller speed to maintain a 1:1 ratio between them.

It will be very interesting to see what real difference did we end up seeing between using DDR5 at 5200MHz and DDR5 at 6000MHz with the new Ryzen 7000, and if the performance difference between the two really justifies the higher cost, or if the opposite ends up happening. We found very little difference with the Ryzen 5000 for the 3200MHz, 3600MHz and 4000MHz DDR4 memory sets, so this may happen again.