Originally Posted by TK421
What do you mean odd memory ratio?
The kit is 3000C15 B-die (4x16GB), can't even get it to boot at 2800/2933 (20-20-20-44 2T 1.4v) at strap 100.
8x16GB loses channel 3 even with 2133 20-20-20-44 2T 1.4v 100 strap. So only reading channel 1-2-4 with total 96GB.
VCCSA / VCCIO (imc) is set at 1.19v, CPU reverted back to stock settings.
Changing strap requires reconfiguration of CPU multipliers or?
(all those extra carriage returns in your post are deleted in the quote, so I don;t have to hunt for a sentence - why do that?)
The memory ratio (or memory multiplier) is the ratio between BCLK(strap) and the frequency (Hz) not the ram speed (eg, 2666, or 3000 etc), or data rate (DDRx). THe ram frequency is shown in CPUZ, the speed is double the frequency).
So for 2666 on strap 100, the ratio is 133, on 125 strap, it is an "odd ratio" (x99 only does 100 and 133 "dividers"). On your MB, the best ratios are 2666/100, 3200/100, 2800/100(?), 2750/125, 3400/100. About the same as x79 (just from "recollection").
A very crude
way to determine if a ram kit is actually faster as a starting point is to divide the frequency by CAS. So..
4000cas17 ~ 235
3600cas16 ~ 225
3600cas17 ~ 212
2666cas12 ~ 222 and...
3000cas15 ~ 200 (which is the "slowest" in this list)
This is the theoretical data rate (higher is better). The higher the freq/cas ratio... the better the "bin" for the rated speed (this will not reflect overclocking headroom or voltage-frequency scaling above the rated speed)
Speed is not bandwidth. Think of bandwidth as lanes on a highway, with everybody driving the same speed. More lanes (channels) higher bandwidth, but the "speed" is the same whether it's 2 lanes (dual channel) or 4 (quad channel) running the same frequency and primary timings. Of course secondary and 3rd timings will impact any measure of ram performance...
On x99 quad channel (socket 2011-3) with a good cpu and decent ram ICs (20nm B or 17nm D die, 8GB sticks) most x99 boards can do 3200 some can do 3400 at 1.45V or less. 16GB sticks on x99 will always be a challenge at 2666 and higher.
Eh, it's a really dense subject, and unless we invest the time, tuning can be a real rabbit hole. You can get a lot of info and examples in the Intel 24/7 ram thread here at OCN.
2666 with as low a cas as you can get is just fine. running a higher frequency with a higher cas may not improve performance at all