Overclocking, Tuning, Bandwidth And Latency
This CPU doesn’t work beyond a 132MHz base clock, so stepping past DDR4-3168 (132 x 24) requires me to increase the DRAM ratio and “underclock” the 100 x 1.25x BCLK. Because the Vengeance LPX wouldn't reach DDR4-3168, that step wasn’t necessary.
That’s not to say the Vengeance LPX DDR4-2666 is a bad overclocker though; its maximum-stable DDR4-3119 easily beats the DDR4-3071 of Kingston’s DDR4-3000.
Best Stable Timings
Corsair Vengeance LPX DDR4-2666 also edges out the best timings of Kingston’s DDR4-3000. That should help it in a few benchmarks, though there are secondary and tertiary timings left to “automatic” mode that could have some effect.
Reconfiguring DDR4-2666 from this motherboard’s 21.33 x 125MHz custom overclock to a more broadly-compatible 26.66 x 100MHz required several adjustments, which, through the magic of Photoshop, are combined in a single screen shot.
Dropping the BCLK ratio (CPU Strap) from 1.25x to 1.00x (125 to 100MHz) automatically causes the actual BCLK setting to fall to its stock 100MHz. Though the motherboard automatically lowered the CPU cache ratio to 24x when setting the 1.25x strap, it did not automatically restore its 30x default when forced back to the 1.00x strap. After resetting CPU Cache to 30x, I changed the CPU multiplier from 32 (32 x 125 = 4000) to 40 (40 x 100 = 4000). Since the motherboard’s 21.33 x 125MHz data rate (DDR4-2666) was now at 2133MT/s, I also had to manually set the memory to 2666MT/s.
In spite of motherboard readings, my voltmeter shows that the board’s 1.330V setting produces an actual 1.35V to 1.36V.
Seen in the Vengeance LPX “Rated Data Rate” value, its DDR4-2666 bandwidth suffers slightly from loose 15-17-17-35 timings. Capable of far better, its manually-optimized DDR4-2400 timings match Kingston’s in both setting and bandwidth.
Loose timings likewise hurt Corsair’s rated DDR4-2666 settings in Sandra's latency measurement, though manually-optimized timings are again roughly tied with Kingston's DDR4-3000. Remember, lower is better for latency.