Solving for RAM with a boost clock CPU
Solving for RAM with a boost clock CPU
I know the fundamentals of RAM overclocking and adjusting the fclk with AMD. I'm trying to understand how this affects the boost clock. If the CPU keeps changing its speed, how do I ensure the RAM stays in sync? Am I missing something important? I'm weighing a choice between 3600 MHz and 3200 MHz for the Ryzen 9 5900X, which has a base clock of 3700. My idea is to slightly increase the RAM speed to match the base clock, which should fit within the Infinity Fabric's limits, but then I worry that frequent CPU boosts might disrupt synchronization and push the RAM into asynchronous mode.
Hi Jagscorpion
Official support for the 5900x reaches up to 3200Mhz.
You may opt for 3600Mhz OC RAM, but there won’t be a D.O.C.P profile available for straightforward overclocking; you’ll need to manually input timing and voltage details in the BIOS.
The performance of the chips depends largely on their IMC strength, which affects whether you can hit the rated speed without certainty.
Aiming for a perfect 1-1 ratio between fclk and mclk is ideal, and AMD suggests using DDR4-3600 with an FCLK set to 1800 MHz for best results.
If boost stability is an issue, consider manual overclocking across all cores as I have done.
Hi Jagscorpion
Official support for the 5900x reaches up to 3200Mhz.
You may opt for 3600Mhz OC RAM, but there won’t be a D.O.C.P profile available for straightforward overclocking; you’ll need to manually input timing and voltage details in the BIOS.
The performance of the chips depends largely on their IMC strength, which affects whether you can hit the rated speed without certainty.
Aiming for a perfect 1-1 ratio between fclk and mclk is ideal, and AMD suggests using DDR4-3600 with an FCLK set to 1800 MHz for best results.
If boost stability is an issue, consider manual overclocking across all cores as I have done.
No connection between CPU and RAM affects their OC. Syncing frequencies isn't necessary. The RAM controller in Ryzen chips is separate and manages synchronization. Based on your memory size and BIOS settings, the FCLK will automatically adapt to memory XMP, allowing manual adjustment of RAM speed up to the maximum allowed by the memory and BIOS. Zen3 supports memory speeds above 4000MHz, while others depend on the memory type.
PS.
Increasing RAM frequency by 100MHz won't yield real benefits and might even reduce performance if Cl or latency settings are adjusted.
It varies based on the model and its BIOS settings. For example, my specific model can reach a DOCP of 4000MHZ with a FCLK of 2000, even though its installed RAM is 3600MHz when using XMP.
Genius? Maybe, but there wasn't anything truly genius about this. Got stuck RAM in the right slots (A2 and B2), turned on DOCP 3600 at 3600 MHz (second XMP setting) and it worked. Checked FCLK and it was 1800, so everything ran smoothly even at Cl 18 (XMP said it should be 17).
The second part might seem odd. By accident, I adjusted DOCP to 3000 and frequency to 3600MHz, and now it works at 3600MHz but with Cl 16. Checking the Dram calculator showed several settings were off, and it broke the 51000 point limit in the Aida test.
At 3800MHz it was another issue; I had to do everything manually with help from the Dram calculator, but Cl increased to 26, making it slower even though the frequency was higher. 4000MHz at a ridiculous Cl 37 was almost impossible to use. I posted but didn't enter Windows or Linux, too much of an OC stretch for this memory, although it's a b-die.
I was considering getting proper 4000MHz RAM, but it's too costly for the diminishing returns. The 500 series chipset MBs and Zen3 can handle much better and more easily.
The Geardown mode (GDM) is turned on automatically when using DDR4-2666, which makes even tCL, tCWL, tRTP, tWR and CR 1T work. To run odd tCL, turn off GDM. If you're having issues, try running CR 2T, though this might reduce the performance benefits of lowering tCL and could be less stable than using GDM. For instance, attempting DDR4-3000 CL15 with GDM enabled causes CL to be rounded up to 16. Regarding performance, disabling GDM results in better CR 1T speeds compared to GDM enabled CR 1T or disabled CR 2T.
I have a comparable setup.
Asus Prime X570
R5 3600
16 GIG Corsair (Samsung die) 3600 XMP running without issues.
Successfully lowered from 20-23-23-43-66 1T to 18-19-19-43-67 1T without problems.
Checked my settings and found the XMP profile is set for 3596, not 3600, showing 1799.
Close enough.