1:1 or decoupled Fclk/Memory?

[Ripred]

I've seen this topic go both ways in terms of gains and losses to performance and no clear guidelines for do's and don'ts if interested in trying, From what I heard originally was decoupling has some sort of penalty, atleast with past Ryzen I'm unsure about the current situation but I've heard the penalty can Be made up into gains, is this function worth experimenting with, what are the penalty's if any, what voltages for managing stability?

[RONOTHAN##]

On Ryzen 3000/5000 there was a massive latency penalty when running decoupled, and unless you managed to clock the FCLK very high with memory speeds in excess of 4400MT/s+ you couldn't overcome the performance decrease in most situations. For daily operation in general you're better off sticking to ~3800MT/s so you can stay in 1:1 mode for the best latency. 

 

On Threadripper, there was already a massive latency penalty, so running memory decoupled doesn't really have much of a downside, though when you're running the amount of memory you're likely to be running with a Threadripper rig you'll likely be stuck running at speeds where 1:1 makes more sense. 

 

On Ryzen 7000 theres no such thing as 1:1 mode as the MCLK and FCLK have been fully decoupled from each other, so you want to clock both as high as you can. 

 

9 minutes ago, lotus10101 said:

what voltages for managing stability?

On Ryzen 3000/5000 (haven't personally messed around with Threadripper or Ryzen 7000 yet so can't give any commentary on how those work), the biggest one is the SOC voltage, this will tend to sweet spot between between 1.1 and 1.2V on most chips, with 1.15V generally being considered "good enough" for 95% of CPUs. The VDDG voltages also help with some memory/FCLK overclocking, though in my experience the motherboard sets them well enough that they're not worth touching. The 1.8V rail also helps with FCLK overclocking, but this is more for competitive overclocking than daily operation as I've never had it get settings that were unstable to fully stable by raising it, only to mitigate the performance penalties from running unstable settings in some workloads. 

[Ripred]

There's no 1:1 on the 7000's ? 

 

Wouldn't that mean they have a penalty, or was that penalty built in to the previous gen?

[BotDamian]

5 hours ago, RONOTHAN## said:

On Ryzen 3000/5000 there was a massive latency penalty when running decoupled, and unless you managed to clock the FCLK very high with memory speeds in excess of 4400MT/s+ you couldn't overcome the performance decrease in most situations. For daily operation in general you're better off sticking to ~3800MT/s so you can stay in 1:1 mode for the best latency. 

 

On Threadripper, there was already a massive latency penalty, so running memory decoupled doesn't really have much of a downside, though when you're running the amount of memory you're likely to be running with a Threadripper rig you'll likely be stuck running at speeds where 1:1 makes more sense. 

 

On Ryzen 7000 theres no such thing as 1:1 mode as the MCLK and FCLK have been fully decoupled from each other, so you want to clock both as high as you can. 

 

On Ryzen 3000/5000 (haven't personally messed around with Threadripper or Ryzen 7000 yet so can't give any commentary on how those work), the biggest one is the SOC voltage, this will tend to sweet spot between between 1.1 and 1.2V on most chips, with 1.15V generally being considered "good enough" for 95% of CPUs. The VDDG voltages also help with some memory/FCLK overclocking, though in my experience the motherboard sets them well enough that they're not worth touching. The 1.8V rail also helps with FCLK overclocking, but this is more for competitive overclocking than daily operation as I've never had it get settings that were unstable to fully stable by raising it, only to mitigate the performance penalties from running unstable settings in some workloads. 

 

I agree, I have a AMD /900X 12 core Zen4 and it truly seem like doing "synced FCLK" doesn't do anything, in games or in Cinebench, like has the same result, the only thing that changes is that the power consumption seems to be lower. I run my SOC at 1.1v 2x 16GB 5600Mhz CL36 DDR5.

[GuiltySpark_]

38 minutes ago, lotus10101 said:

There's no 1:1 on the 7000's ? 

 

Wouldn't that mean they have a penalty, or was that penalty built in to the previous gen?

Yeah back in August AMD touched on it. 

 

Quote

Now as per Robert, we now know that the default FCLK for AMD Ryzen 7000 CPUs is set to 1733 MHz. Robert also states that memory overclocking is a little bit different with Ryzen 7000 since 1:1:1 (FCLK:UCLK:MCLK) isn't important anymore. It is mentioned that to achieve the best results, you should leave the FCLK to auto and overclock the memory modules and memory controller in 1:1 mode. There will be some corner cases where users will be able to get better performance results by hitting over 2 GHz FCLK speeds but those aren't a big priority, as AMD mentions.

https://wccftech.com/amd-confirms-ryzen-7000-ddr5-6000-memory-sweet-spot-auto-fclk-recommended-for-overclocking/ 

[Ripred]

hm, interesting

I'm just curious why previous gen would get penalized