HyperX HX421C14FBK2/16 Review

If you are not planning to do any overclocking experiments with your memory, you might as well skip this page as it will feature nothing but the information on how to formally void your warranty.

To perform the overclock-testing, we have armed ourselves with a platform that is based on Intel's latest generation of CPUs, that is commonly known as Skylake.

 CPU  Intel Core i7-6700K (running at 4.5 GHz)
 Motherboard  MSI Z170A Xpower Gaming Titanium Edition
 (BIOS version 1.0P)
 Memory  Kingston HyperX Fury HX421C14FBK2/16
 Graphics card  ASUS HD4350
 Storage  Kingston SSDNow V300 60GB
 Power supply  Seasonic Platinum 1200W
 Operating System  Windows 8.1, 64-bit

There are many ways to test stability of the system but our method of choice is HCI Memtest as it is the toughest memory stresstest that we are aware of. As we are dealing with a 16GB kit on a CPU that can handle 8-threaded load, we use eight 1500MB instances and call things stable if we see all of them run past 150% without showing a single error. Each pass of such a test takes about 50 minutes to complete.

Our test platform has a very wide range of memory clockspeeds to choose from, but to keep things simple we will only concentrate on DDR4-2666, -2800, -3000, -3200 and -3333 modes leaving the intermediate options out as potentially irrelevant. Once we select the memory frequency, we seek for optimal combinations of primary timings, for which we minimise the stable voltage in 0.01V increments.

When overclocking Hynix-based memory modules we usually observe the following behavior. If the CAS latency is kept without change, then the dependency between stable frequency and minimal stable voltage is close to linear. What comes to the rest of primary timings (tRCD, tRP and tRAS): the minimal stable values depend primarily on the memory frequency with voltage playing a secondary role in the borderline areas. However, on Skylake you also have to keep in mind that tRCD must be equal to tRP at all times and that the minimal tRAS value one can set in the BIOS is 28.

Below you can see the list of stable configurations that we were able to achieve with our sample.

1333MHz (DDR4-2666)
1400MHz (DDR4-2800)
1500MHz (DDR4-3000)
 CL10
not possible
not possible
not possible
 CL11
11-14-14-28 @ 1.54V
not possible
not possible
 CL12
12-14-14-28 @ 1.39V
12-15-15-28 @ 1.47V
not possible
 CL13
13-14-14-28 @ 1.30V
13-15-15-28 @ 1.36V
13-16-16-28 @ 1.46V
 CL14
14-14-14-28 @ 1.23V
14-15-15-28 @ 1.27V
14-16-16-28 @ 1.36V
 CL15
15-14-14-28 @ 1.17V
15-15-15-28 @ 1.21V
15-16-16-28 @ 1.28V
 CL16
not relevant
16-15-15-28 @ 1.16V
16-16-16-28 @ 1.22V
1600MHz (DDR4-3200)
1666MHz (DDR4-3333)
 CL14
not possible
not possible
 CL15
15-17-17-28 @ 1.35V
not possible
 CL16
16-17-17-28 @ 1.28V
not possible

We did not bother to test the kit at its rated speeds, but it is obvious from the DDR4-2666 CL14 result which only took extra 0.03V that clearing 1066MHz will never be a an issue.

Moving on to higher voltage has enabled us to achieve full stability DDR4-3000 and DDR4-3200. Of course, some of the timings had to be relaxed but hitting specs of some 3200C15-rated models is not too shabby for a kit whose rated clockspeed is 1.5x lower. DDR4-3333 was not stable even after loosening the latencies to 18-18-18.

To see the practical gain of overclocking the memory, we made a quick performance comparison using AIDA64 Cache&Memory test, CineBench R15 and XTU. Note that we have slightly optimised the secondary timings and you can also use our values as a starting reference.

HX421C14FBK2-16_performanceDEF HX421C14FBK2-16_performance1500c13 HX421C14FBK2-16_performance1600c15

The performance gain in synthetic benchmarks (AIDA64 and XTU) is more than noticeable, however, in tests that only concentrate on raw CPU power, the gain is just 2 per cent.

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  1. The best cheap memory for a nowadays skylake architecture PC.
    I buy these with B150 MOB, i3-6100 CPU, and GTX 1050 Ti GPU.
    It’s enough for common using and some gaming with low consumption.