6800K crazy reduction in VCCSA voltage with 3000mhz ram

[moonbogg]

I was at 3200mhz cas16 and needed 1.27 SA voltage to be stable. Someone suggested reducing the ram speed so I could lower the SA voltage. It never occurred to me to try that because its sort of blasphemous and sacrilege, but I tried it.
So far its running stable at only 1.1 SA voltage with ram at 3000mhz, cas 15, command rate 1. So the bandwidth and performance is basically the same as before due to lower cas settings, but for some reason it requires way less voltage to be stable.
I just thought it was very odd and totally unexpected for the chip to hate 3200mhz so much. At 3200mhz and around 1.1 SA voltage, it wouldn't even post. Also, It doesn't even care about the cas latency. It just hates those extra 200mhz. Is that unheard of for you guys too? Maybe you aren't surprised by it but I am. Crazy.

 

[disappoint]

My guess is the higher frequency is causing RF interference onto the chip itself. The higher voltage is required to overcome the noise when you raise the noise floor like that. It's all about SNR (signal to noise ratio). The lower frequency lowers the noise floor increasing the SNR requiring lower voltage to maintain the necessary SNR for the chip to function properly.

 

[moonbogg]

^ Interesting. I was totally going to say that.

 

[Carfax83]

It's weird how each chip differs in capability when it comes to memory speeds. My old 5930K could run at DDR4 3200 (but no higher) at 1.18v SA and the memory controller at 3.6ghz or so if I remember. It could hit higher frequencies for the memory controller, but it was unstable and the performance gain wasn't worth it.

My 6900K on the other hand can do DDR4 3400 CL15-15-15-34 CR1 tRFC 300 with memory controller at 3.4ghz with only 1.064v on the SA. It could possibly do more, but I haven't tested it.

 

[Edrick]

My 6900K on the other hand can do DDR4 3400 CL15-15-15-34 CR1 tRFC 300 with memory controller at 3.4ghz with only 1.064v on the SA. It could possibly do more, but I haven't tested it.

My 7820X can do 3200mhz CL15 at 1.054v on the SA. VCCIO is only at 0.875v. Really like these Skylake X cpus and their low voltage requirements.