Intel Skylake DDR3 vs. DDR4 Comparison
Although the DDR4 standard was established all the way back in 2012, nobody really cared about it until its appearance on the Haswell-E LGA2011-v3 platform. Even then, since that high-end platform is such a niche product anyways, it is really the arrival of Skylake-S that has forced your average consumer to start paying attention to this new memory standard.
As always happens with new memory standards, DDR4 started out with a gross price premium over DDR3. However, a quick price check reveals that DDR4 memory kits have essentially come down to parity with their similarly-sized DDR3 counterparts. The reason for this is that the industry transition from DDR3 to DDR4 is heavily underway, largely motivated by the enterprise and mobile markets, and thankfully the DIY desktop market gets to benefit from the lower prices caused by larger production volumes. As a result, with the price obstacle out of the way and the DDR4 performance deficit argument largely settled, has DDR3’s time finally come to an end?
When it came to pure memory performance, the memory bandwidth difference between our DDR3-2400 and DDR4-2400 systems was only about 2.5% when it came to read speeds, 7% for write speeds, and 4% for copy speeds, all in favor of DDR4 . With the timings that we set, which we felt accurately mirrored the average timings of currently available memory kits, the DDR3 system did achieve 2.5% lower latency figures. These aren’t dramatic differences, but that’s because we are comparing two unevenly matched configurations. Whereas DDR3-2400 is near the top-end of the spectrum for DDR3, DDR4-2400 is considered relatively lowly in the DDR4 realm. If we compare the DDR3-2400 to DDR4-3200, the memory bandwidth gains are 32% read, 41% write, and 32% copy. That is pretty significant, but does it translate to real-life performance gains?
Well, when we compare the system and gaming benchmark results between our DDR3-2400 and DDR4-2400 configurations, there is very little difference. The DDR3 system occasionally took the lead, but overall DDR4 consistently inched ahead. It might sound obvious, but to see the performance benefits of the additional memory bandwidth provided by DDR4 you need a memory bandwidth intensive workload. There aren’t a ton of those on the consumer side, but WinRAR file extraction is one of them and the performance difference was significant. There was a 7.5% gap between the identically clocked DDRx-2400 configurations, and a 20% improvement between the fastest DDR3-2400 and DDR4-3200 results. Sure, we could have tried DDR3-2666 or even DDR3-2800, but the economics just don’t make sense since those elite DDR3 kits are often twice as expensive as comparable DDR4 kits. Furthermore, no matter the results, we would never recommend that anyone actually go out and buy expensive DDR3 at this point anyways, since DDR4 is the future in terms of compatibility with upcoming platforms.
In the introduction, we wondered whether DDR3’s low clock speeds and resulting lack of bandwidth would hold back the performance of a Core i7-6700K. Based on our results, we have to say both yes and no. There are definitely instances when run-of-the-mill DDR3-1600 or even DDR3-2133 will be a bottleneck, but the numbers just aren’t significant enough for us to sincerely recommend that you need to buy a DDR4 kit if you’re trying to upgrade on a tight budget. If you already have a highly clocked DDR3 memory kit, definitely consider using it in a Skylake build. You will save money and achieve comparable performance to DDR4, but you need to be comfortable with the possibility of potential IMC damage and accept that no matter what there is an eventual DDR4 RAM purchase in your future.