G.Skill 2x1GB DDR3 PC3-12800 Review

Our stability testing methods for memory have been discussed at length in the past, so we are going to simply rely on the explanation from previous reviews. Here is a run-down of what we consider to be proper stability testing.

Memory stability, what constitutes stable? What is not considered stable? These questions get hotly debated in enthusiast forums all over the internet like little brush fires on the fringe of an inferno that play havoc with forest fire crews. Everyone has their own opinion about stability, especially when it comes to memory stability. For some, stable means they can do whatever it is on their computer without it crashing, blue-screening, or restarting; whether that means gaming or simply surfing the internet. To this user, stable means simply using the computer as they normally would.

Of course, that is not what we would call stable and we do a lot more thorough testing before labeling a memory frequency/timing stable. One of the toughest types of programs on a system has been found to be distributed computing projects such as Rosetta@Home, Folding@Home, World Community Grid, and more. Running 24/7 crunching for one of these great causes is a sure way to find holes in a system if there is truly some instability, unfortunately it takes a considerable amount of time to use them for stability testing so we use the list of programs below to all but guarantee the system to be 24/7 distributed computing stable:

• Multiple loops of 3DMark 01 / 06 (30 minutes of looping the full tests each)
• Dual 32M runs of SuperPi Mod 1.5 (ran at the same time)
• 2 hours of dual Prime95 using Prime95 v25.4 Stress Testing Blend
• 2 hours of dual HCI MemTest Pro in Windows using 850MB/instance

The above testing is quite exhaustive and has been found to provide us with a system that is stable and willing to run a distributed computing program 24/7 or hours of gaming without interruption or failure. This method of stability testing will not only be used for testing the stability of the overclocks but also the rated specifications outlined by the manufacturer. We have added the Specification Stability Testing section in response to finding a few kits of DDR3 memory not being able to stably run the specified frequency/timings at the rated voltage.


Specification Stability Testing:

This section is dedicated to testing the specifications of the memory modules in question for stability using the outlined method above. There have been a recent number of reports of DDR3 memory kits not meeting the specifications from a lot of users so this section was added to see how each set of modules we review stack up to their specifications.

The rated specifications of the G.Skill HZs are not that demanding so we were not expecting much of a fight in this section and we were right. These modules run their specifications basically blindfolded and with very little effort on our part as far as adjusting secondary timings to get them stable goes. In-fact, secondary timings are left on AUTO as we don't have to adjust them and the voltage is set to 1.80v (actual) instead of the rated 1.9v.

As mentioned, this kit passed our stability test at specification more than easily with even lower voltage than specified. This means that we should see some pretty decent overclocking and that is what we are going to get to next.

There is one major caveat that needs to be discussed before we look at the overclocking results. What you set in the BIOS isn't always what you actually get, especially when it comes to voltages. Because of this, we don't list the voltage selected in the BIOS, or the voltage read by software for vDIMM. Instead, we base our voltages on the actual voltage being supplied to the modules with a calibrated UEI DM393 digital multi-meter that is getting a reading directly from a VTT pin in one of the open DIMM slots. This means the voltage listed is the actual voltage that was being supplied and is represented in the screenshots by way of a small text file. The Everest vDIMM reading is usually 0.04v above what is actually being supplied.

Keep in mind that these results are from a single sample being tested on a single motherboard. There is no guarantee that the below results will be achieved from every kit of memory G.Skill sends out as the variables are endless. With that said, let's see what these G.Skill HZs were capable of:

A steady climb from left to right is what we are looking for and at all three timing sets this is what we receive. Starting off with a look at the 6-6-5 timings we see that 800MHz stable was achieved with 2.06v and almost accomplished with just 2.00v. The reason we stop at 2.06v is because it is still quite unknown how much voltage is too much voltage for DDR3 memory sporting Micron D9 IC's but with 2.00v being under warranty by many manufacturers, we figure 2.06v should be safe as well.

At 7-6-5, these modules simply excel and at the rated voltage of 1.90v, our sample clocked up to over 860MHz which is well over spec and at much tighter timings. Loosening the timings up to 7-7-7-18 would provide even further headroom at the various voltages. These modules have no problem crossing 900MHz at 2.0v which puts them right up there with some of the highest rated DDR3 being offered by other manufacturers and for DDR3-1600 rated modules, is quite impressive.

The 8-7-6 clocks are also nothing to sneeze at but it appears that not only is memory being limited on the P5K3-Dlx we use but also the Maximus Extreme. Further increasing the voltage to 2.06v did not provide even 2 MHz further overclocking headroom at 8-7-6 and it would appear to be the motherboard holding it back. DDR3-2000 is still very nice an achievement for this memory but there would appear to be more available. Here are the screenshots of the highest overclocks for each timing set.