Optimizing Infinity Fabric with 3200 MHz ram and 5600x

[Sagely Hijinks]

So simple question. I have this kit which is rated to run at 3200 MHz. From what I've heard, it's Micron E-die and should be able to overclock to 3600 if I loosen the timings? (not positive, I'll read up on it when my system is closer to finished being put together).

 

So basically, here's my question. I've heard that the Infinity Fabric really likes a 1:1 ram speed:CPU speed ratio, and also that the Zen 3 chips run at 1900 MHz. So ideally, I think, you'd want 3800 MHz RAM.

 

So how do I get the most performance out of my PC? Do I lower the CPU clock to 1800 to match the overclocked RAM? Do I try to overclock the RAM even further to match the CPU? Do I not bother and let them both sit at more or less stock?

 

Any advice? I've had issues finding the answers to these questions, but maybe I've been looking in the wrong places.

[Jurrunio]

38 minutes ago, Sagely Hijinks said:

:CPU speed ratio, and also that the Zen 3 chips run at 1900 MHz

that's infinity fabric frequency. CPU speed typically refers to CPU core frequency, which is a very different thing.

 

39 minutes ago, Sagely Hijinks said:

Do I lower the CPU clock to 1800 to match the overclocked RAM?

Yup. Basically the finding is that unless you can crank FCLK on or over 166MHz higher than if you keep it sync with memory frequency, keep it in sync.

[-rascal-]

1 hour ago, Sagely Hijinks said:

So simple question. I have this kit which is rated to run at 3200 MHz. From what I've heard, it's Micron E-die and should be able to overclock to 3600 if I loosen the timings? (not positive, I'll read up on it when my system is closer to finished being put together).

 

So basically, here's my question. I've heard that the Infinity Fabric really likes a 1:1 ram speed:CPU speed ratio, and also that the Zen 3 chips run at 1900 MHz. So ideally, I think, you'd want 3800 MHz RAM.

 

So how do I get the most performance out of my PC? Do I lower the CPU clock to 1800 to match the overclocked RAM? Do I try to overclock the RAM even further to match the CPU? Do I not bother and let them both sit at more or less stock?

 

Any advice? I've had issues finding the answers to these questions, but maybe I've been looking in the wrong places.

 

How much looser do the timings need to be?

The kit is already DDR4-3200 CL16.

Overclock to DDR4-3600 while maintaining CL16 timings, or needing to loosen it to CL18, CL19, or CL20?

 

At that point, your DRAM frequency is faster, sure, but your performance is hindered by the CL18 or CL20 timings. If you need to run CL18 or CL20 timings for DDR-3600...might as well keep it at rated DDR4-3200 CL16.

 

DRAM frequency and timings go hand in hand. DDR4-3200 CL14 actually performs slightly better than DDR4-3600 CL16.

 

DRAM : Infinity Fabric : NB

Is 1:1:1 up until 1900 ~ 2000 MHz.

Infinity Fabric is the communication bus between the CPU cores/chiplets.

CPU frequency is separate.

 

 

[porina]

If faster ram (more bandwidth) or lower latency (tighter timings) help more for an application depends a lot on the application. You can't just say lower latency is better.

 

There's also another option I don't see mentioned: run infinity fabric async. This was a trick for Zen 2, I presume it can be similarly done on Zen 3 also. Run your mem at rated speed, and only increase IF (FCLK). This helps in scenarios where IF (and anything timed off it) is the limiting factor, although it might possibly go against latency sensitive use cases. You'll have to do testing for what's important if you go this route.

 

BTW I'm really not a fan of OC ram for day to day use. The risk of undetected stability problems is much worse than CPU OC.