G.SKILL F2-6400CL4D Review

Author: William Henning
Editor: Howard Ha
Publish Date: Tuesday, April 3rd, 2007
Originally Published on Neoseeker (http://www.neoseeker.com)
Article Link: http://www.neoseeker.com/Articles/Hardware/Reviews/gskill_pc6400/
Copyright Neo Era Media, Inc. - please do not redistribute or use for commercial purposes.

Sometimes when you look at the market for performance memory it is easy to forget that not everyone is going to automatically look for PC2-8000, PC2-8500, or the new PC2-9200 speeds that scream high bandwidth and high prices.  The fact is that high performance also includes ultra low latencies at PC2-6400, a segment which promises excellent performance, decent pricing, and most importantly for the enthusiast: overclocking potential.  Today we are looking at G.Skill's low latency PC2-6400 modules - the F2-6400CL4D-2GBHK kit that comes with a matched pair of 1GB modules, and promises a very low 4-4-3-5 latency at 800MHz with memory voltage running  between 2.0V-2.1V.  Given the quality of memory these days, many enthusiasts,myself included, often get PC2-6400 memory with ultra tight timings and push them to the limit, and as usual that's what I intend to do with these G.Skill modules.

The modules have a simple looking heat spreader on them, with an attractive embossed logo. Unfortunately the heatspreader cannot be removed without tearing or otherwise removing the factory sticker; however at least the sticker has the timing specifications and voltages written right on it. The heatspreader appears to be attached to the memory chips with a standard thermal transfer tape - a less than optimal approach, however quite acceptable for a memory device rated in the PC2-6400 range.


Capacity 2GB (1GB x 2)
Speed 800MHz DDR2 (PC2-6400)
CAS Latency CL 4-4-3-5
Test Voltage 2.0~2.1 Volts
PCB 6 Layers PCB
Registered/Unbuffered Unbuffered
Error Checking Non-ECC
Type 240-pin DIMM
Warranty Lifetime

Test Setup

For this review, we again chose the best performing Intel 975X motherboard we had in house, our excellent Asus P5W DH, and paired it with an Intel Quad Core QX6700!  We will be comparing the G.SKILL PC6400's with some of the best modules out there - like the OCZ FLEX XLC and the power house Corsair Dominator PC2-8888 which we reviewed last month. Needless to say, this should prove extremely interesting, interesting indeed.


Software used during testing consisted of the following:

In order to keep the testing as fair as possible, we will use the following test platform:

As normal, we'll discuss our overclocking adventures at the end of the article. However, for the results you'll see in the following pages we include overclocked benchmarks to show you what gains you could expect if you also achieved similar overclocks - our test sytems were all stable at the settings shown with air cooling, thanks to ourNoctua NH-U 12 CPU cooler. The chart labels incorporate a lot of information about the test configuration. The first line shows the socket type and the model of the processor. Since all the processors shown are dual/quad core devices, we did not specify that on the charts, but simply the processor type for reader reference.

The second line shows the "FSB/HT clock rate" x "CPU multiplier" and the effective DDR memory speed. Please note that all DDR2 tests were run at 4-4-4-12 timings where possible.

One change from our usual testing strategy that needs to be highlighted out is that the Asus P5B-E results for the OCZ PC2-9200 were obtained with an Intel E6400 processor as that was the chip installed in that particular board at that particular time. The two core vs. four core issue is moot as the memory benchmarks are not multi-threaded (Doom might slightly benefit from the additional cores) and while the 4MB vs. 2MB cache size differences will cause some performance differences, they will be relatively minor for the purposes of this review.


As usual, I will be concentrating on seeing how far I can push the G.SKILL PC6400 memory compared to these other  DIMM's - how fast can they go with a 4-4-4-12 timing?

Given that the 975X is currently one of the best chipsets available (especially for memory), it is not surprising that we were able to obtain excellent results. What you may find surprising is just how much "headroom" these dimm's have for being pushed beyond specifications...

Ok, enough talking... let's get on with the testing! 


The 4-4-3-5 timing allowed the G.SKILL PC6400 memory to take the top spot at 800MHz among the three PC6400 modules tested. The overclocked results for the G.SKILL PC6400 were quite good; it managed to reach 975MHz at 4-4-4-12 timing.


RightMark Read

The G.SKILL PC6400 read performance at stock speeds was where we would expect it, and it turned in a decent performance when overclocked to its maximum stable speed at 975MHz with 4-4-4-12 timing.

RightMark Write

No suprises here. At stock speeds, the G.SKILL PC6400 did as one would expect; and it turned in decent numbers when overclocked.

Do not let the much more expensive modules better overclocked results deter you from considering it.

RightMark Latency

The G.SKILL PC6400 superior low latency timings at 800MHz did not manage to make it stand out - the lack of an integrated memory controller is limiting the effectiveness of low latencies.

RightMark Bandwidth

The G.SKILL PC6400 did surprisingly well here considering its price; it even beat some much higher rated modules.


WinRAR liked the G.SKILL PC6400 - it did extremely well for its official rating, WinRAR appears to be able to take better advantage of the low latency the modules offer - and when overclocked, it was practically neck and neck with much higher rated, far more expensive modules.

Doom 3

Doom 3 also liked the G.SKILL PC6400's - for Doom 3, its performance was excellent considering its rating and price; it noticably outperformed much higher rated modules.



In my experience, quality memory modules have a lot of "headroom" left over for overclocking. Would I overclock a mission critical business system? Heck no! But it sure is a nice way of getting some extra mileage out of your system without spending waaaaay too much for a few extra FPS.

The G.Skill PC6400 modules ended up running at up to 975MHz at 4-4-4-12 timing - that is 175MHz above the rated 800MHz speed; a 21.9% increase in raw memory clock rate. We have seen higher memory speeds, but it is still fairly impressive to see a PC6400 module reach PC7800 speeds.

In order to reach 975-4-4-4-12 stably, I had to increase the memory voltage to 2.35V. The modules were quite warm, but they were not too hot to touch, however even increasing the memory voltage to 2.4V did not get them stable at 1000MHz. I was using a 1.45Vcore, 1.65 Northbridge, 1.45 FSB voltage setting.


Can you get faster memory than the G.Skill PC6400?


Can you get faster memory that will overclock higher than the G.Skill PC6400?



If you get the G.Skill PC6400, you are still getting pretty damn good memory, and spending a lot less money than those PC8500 or higher modules. Don't get me wrong - if you want to squeeze the last bit of memory performance out of your system, and have the funding available, the higher end modules may actually be a better deal for you - however, I think that for most users, modules such as the G.Skill PC6400 that combine decent performance with a lower price tag may be a good choice.

About the only negative aspect of these modules was the need to boost the memory voltage to at least 2.2V in order to have them run stable at their rated 800MHz 4-4-3-5 timing. Mind you, this could just as easily be explained if the motherboard was not supplying as much voltage to the modules as is configured in the BIOS; and in reality, there was no significant difference in speed between 4-4-3-5 and 4-4-4-12. Frankly, running at 975-4-4-4-12 is a heck of a lot faster (for memory) than running at 800-4-4-3-5! 

To give you an idea why I am satisfied with the G.Skill's performance, let's take a peek at some current pricing from a major web retailer:

Granted, the higher priced modules surpassed the G.Skill in the tests; but for most people, the savings are significant.

Ok, so given the good performance, why is the G.Skill not getting the "Value Award"?

Because the SuperTalent T1000UX2G5 PC2-8000  I recently tested, which was only rated at 1000-5-5-5-15, managed to hit 1069-4-4-4-12 for only $8 more!  G.Skill F2-6400CL4D is still an excellent set of memory with great performance at stock and good overclocking.  It might not be the value king right now but it certainly holds enough value and performance to make it a worthy choice.



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