With memory modules of this calibre, it is fair to assume that a large proportion of the user base will be looking for the kit's highest attainable frequency with good enough stability. That doesn't mean that the ability for the overclocked kit to run every benchmark with stability is crucial, but it does place an importance on being able to boot and run at least one test flawlessly.
We will be tweaking the base clock to fine-tune the memory overclock. Due to the above point, and the fact that the processor frequency will be different to when the RAM was running at stock speeds, there is little point in showing comparison benchmarks. Instead, we will use a single run of Super Pi 16M to verify stability.
As we do not have access to sub-zero testing equipment, we will be relying on tweaks and voltage settings when using an air-cooled system.
We started out by using the 1.25x CPU strap so that we could use a BCLK above the 125MHz-mark for our overclocking attempts. We soon realised that the ADATA XPG V2 modules had plenty of overclocking headroom and we therefore switched to using the 1.67x CPU strap.
To eliminate base clock bottlenecks, we used a number of increased voltages for the CPU and system. The CPU multiplier was dropped to eliminate instability due to a high processor speed.
The tweaks applied included a 1.7015V DRAM voltage, various CPU voltage increases and setting changes for BCLK overclocking stability, and a CPU input voltage of 1.900V. ASRock’s automated settings proved favourable for overclocking performance and didn’t require changing.
Our best result using the stock timings was 3280MHz (164MHz BCLK) using a DRAM voltage of 1.7015V. We did manage to reach the same 3288MHz (using the 1.25x CPU strap and a 137MHz BCLK) that Avexir's Core Extreme Series modules hit using the ASRock Z87 OC Formula motherboard, but stability in Windows was certainly questionable, as proven by two consecutive BSODs.
Our validation with the ADATA XPG V2 3100MHz memory kit running at a 3280MHz DRAM frequency with stock timings of 12-14-14-36-2T can be viewed here.
In order to push further and obtain the maximum memory frequency at 1.7015V, timings were loosened to 14-15-15-40-2T.
The highest memory overclock that we achieved with the ADATA XPG V2 memory modules was 3340MHz, using a 167MHz base clock.
We wouldn't call this a 24/7 stable overclock with our settings, although a little voltage tweaking (with better cooling, perhaps) would have garnered improved stability.
3340MHz was the highest frequency that we achieved; 1MHz higher on the BCLK and the system simply would not boot.
Our validation running at a 3340MHz DRAM frequency with loosened timings can be viewed here.