[SOLVED] CPU Benchmark Dropped 15% After OCing Memory

[Notime4games]

Hi, I followed DRAM Calculator (memory settings from Thaiphoon) yesterday and tweaked my memory from 16-18-18-18-38 at 3600mhz to 15-17-18-18-38 at 3733mhz (1.42 DDR voltage, 1.1 SoC voltage) with Infinity Fabric 1-1 with memory frequency at 1866mhz. All runs smoothly, did a few hours of memory stress tests with zero errors. However, I ran a CPU benchmark using passmark and my score dropped from 33,350 to 29,000 (before and after memory overclock). I ran it a couple times with similar results, and just reverted my memory to base XMP timings and frequency and the CPU benchmark result went right back up to 33,350. Any idea what could be causing the CPU performance to drop when memory timings and frequency are improved? Note that I disabled Power Down Mode and Gear Down Mode when memory was overclocked. CPU is at stock settings.

My system:
Ryzen 3900XT (stock settings)
NZXT Kraken x63 (CPU temps in low 30's c idle and 60's at load, occasionally coming up into the 70s for a couple second)
Crucial Ballistix Gaming memory: 2x8gb (3600mhz CL 16-18-18-38 stock, Micron E die)
Gigabyte Aorus Elite x570 (latest F20 bios)
Sabrent Rocket PCIE 4 NVME SSD

 

[popatim]

The infinity fabric clock drops to 2:1 ratio above 3600 so at 3733 you effective speed is ~1866

 

[Notime4games]

The infinity fabric clock drops to 2:1 ratio above 3600 so at 3733 you effective speed is ~1866

Thanks for getting back. The ryzen 3900 (And some of the others) have an infinity clock which runs 1-1 up to 3733mhz (which is why I chose that as the level to raise my memory frequency to)

 

[Notime4games]

I backed off slightly to 16-18-18-38 @ 3733mhz and then tightened up sub timings. All benchmarks higher than before, and no errors after a few hours of memtest. All good!

 

[popatim]

I believe you are wrong, any mem clock above 3600 results in a 2:1 ratio unless yo manually go in and change the it in the bios. If it's not the IF that drops then its the UMC, I forget, but I'm pretty positive that one of them drops at above 1800

 

[Notime4games]

Sorry, as stated in my original post my infinity fabric is set 1-1 with the memory clock. The 1-1 ratio is possible until at least DRAM frequencies of 3733 (if you read on the online there are people who have run it at 3800mhz 1-1). I can confirm 100% that I am not wrong - my infinity clock is set at 1867mhz. I set it to be that, and can see that it is in fact at 1867mhz.

 

[CountMike]

Sorry, as stated in my original post my infinity fabric is set 1-1 with the memory clock. The 1-1 ratio is possible until at least DRAM frequencies of 3733 (if you read on the online there are people who have run it at 3800mhz 1-1). I can confirm 100% that I am not wrong - my infinity clock is set at 1867mhz. I set it to be that, and can see that it is in fact at 1867mhz.

You are right, 3733MHz is border for IF at !:!:! It just happens that 3600MHz ram usually has best latency/frequency ratio after which you get diminishing gains so it's kinda best deal.

 

[digitalgriffin]

3200 is the preferred guaranteed clock
3600 is the maximum 1:1 clock

There have been demos where jumping any higher forces the fabric to go into a ratio. The videos are online. I have seen multiple examples. But to get any benefit you have to go really fast 4000MHz+. That is a very expensive bump for minimal improvement.

 

[Karadjgne]

The IF limit is finite. If the ram hits 3733.01MHz, it's over the limit. Switches to a 2:1 ratio instantly. Soon as it drops to 3732.99MHz it bumps to a 1:1 ratio again. So the ram spends a lot of time bouncing between ratios, which drops its overall performance boost for faster IF.

This is why the sweetspot for 3rd release Ryzens is 3600, not the actual 3733MHz, motherboards are never exact, nor perfect.

The only way around that is to manually take control of the IF speeds in MCLK, FCLK, UCLK etc, which is serious advanced usage and usually only done on ram speeds of 3800MHz or better.

 

[CountMike]

There are too many variables to stop and say what is better. Everything fro RAM make and model, over what BIOS may offer and all the way to SW/games. This is nice comparison:

View: https://www.youtube.com/watch?v=9IY_KlkQK1Q

 

[popatim]

My infinity clock is set at 1867mhz. I set it to be that, and can see that it is in fact at 1867mhz.

And what was it before you manually set it? I was referring to the automatic setting.
Check your UMC speed as well.

 

[alexbirdie]

3950x, asus crosshair viii hero, mem running with 3733 and manually set IF-clock of 1866. I did not succeed in raising to IF 1900 and therefore mem-clock 3800, but most CPUs should be able to run IF 3733 with 1:1:1. I tightended the subtimings too and all works great. I am running with -0.0750 undervolting and PBO off.

I would like to upload a screenshot of my settings and timings, but obviously it is not possible in this forum. I already asked with 2 mails asking about that to "ContactUS"-mailadress of tomshardware, but nobody answered.

 

[Karadjgne]

Pics are easy. Just need a 3rd party website. I like postimages.org. Click to upload, then hit the hotlink for forums. That puts the Addy in clipboard, so just paste here.

 

[alexbirdie]

Pics are easy. Just need a 3rd party website. I like postimages.org. Click to upload, then hit the hotlink for forums. That puts the Addy in clipboard, so just paste here.

Thx for reply. But I do not have a 3rd party website and I do not want any. I do not want to send ANYTHING into a cloud.