The beginners guide to memory overclocking

Tweaking memory – but where?
For those uninitiated into the world of system tweaking, all the best and most stable tweaks are commonly done on the lowest basic level of the computer system, the BIOS.

Given the nature of the size of the motherboard market and then even the differences between models within a certain manufacturer’s range, we won’t be focusing on a single motherboard BIOS. We will however give some handy hints. These are:

The simplest but most necessary; hit the delete button during POST to enter the BIOS.

The memory tweaking options are commonly associated with the chipset options. This is due to Intel-based systems hosting the memory controller on the North Bridge of the chipset as opposed to on the CPU die as with AMD processors.

Many high-end motherboards now have a dedicated overclocking settings section in the BIOS. To make overclocking easier, common overclocking settings such as FSB frequency, memory dividers, CPU multipliers, PCIe bus frequencies and memory timings are all in the one place.

To obtain access to the advanced memory timings on a GIGABYTE motherboard press the keystroke CTRL+F3 to get access to the settings. This will also open access to additional overclocking settings.

If you’re not sure, test it. If the system fails to boot simply clear the CMOS and load the fail safe defaults and start again!


In voltage power is, hmmm?
As everyone is aware, the voltages of different components in a computer need to each be not only set appropriately for the piece of hardware but be supplied in a consistent fashion. With voltages stable and set appropriately, maximum performance and stability can be obtained from a system.

When it comes to memory it is important to assure the necessary and appropriate voltages are set. This optimum value for the amount of voltage supplied to the memory is dependent on the intended frequencies and latencies. In retrospect, this is first influenced by not only the type of ICs used on the modules but also the bin level they have been obtained from for the module.



It can often be figured out what ICs are on the modules just by the voltages used. Below is as a table of ICs commonly found in the market and the voltages that they run on.

It has become common place for Micron ICs to not only utilise more voltages as a stock reference value given by the manufacturer but also to scale with excessive voltages when pushed to the edge by enthusiasts, especially extreme overclockers.

The responsiveness of Micron D9 chips to additional voltages is a strong reason behind the enthusiast love affair with the IC series. A great example is the great majority of Micron D9 based PC2-6400 C4 kits being capable of 1000MHz to 1100MHz while maintaining common C4 timings sets such as 4-4-4-12 with little voltage adjust necessary. The better quality the IC, the higher the chip can raise the frequency while maintaining tight latencies and using minimum voltage.

Below is a table showing the significant difference between ProMOS and Micron D9 chips at the common voltages of 2.0v to 2.2v. The figures are a common average and taken for reference. There will always be outliers in any batch of chips; however the large majority will stick to the following pattern:




The binning process
Speed binning is progressive and selective testing of all modules destined for a particular product line, for example Corsair’s popular Dominator series. This process allows for the best of the best modules to be pre-tested and selected for use in the top kit from this series. As the quota is achieved for the top level of performance, the binning process continues down throughout the product line, selectively and effectively filtering out the hardware for the given price and performance ranges.

Memory is freaky stuff, as it’s important to know which chips within a given IC range are hot to trot and which are not. For example when the original DDR2 ‘fat body’ D9s (92-ball FBGA) came out, the sexy ICs were the D9DQW and D9DQT chips – the rest were okay but not stellar like these. In the currently available generation (60-ball FBGA), the entry into performance ICs are the D9GCT chips, but the golden boys, like the ol’ fat bodies, are the D9GMH and D9GKX. Now, you’d hope things were simple and aim to get the D9GMH or D9GKX but it’s not quite like that.

The initial release of these two sets in particular showed the D9GKX to be the cream of the crop and the D9GMH second to it. However when looked at closer, it was the initial binning from Micron which was setting these aside. The D9GKX chips were -25E binned while the D9GMH were initially binned for -3 speeds (see Micron binning table for more info).

What this meant was that in the end result, the D9GKX were obtaining higher frequencies with tighter timings and using less voltage to do so. As the manufacturing process was refined, the D9GMH started to obtain -25E binning. When this occurred the enthusiast IC market shifted, the D9GMH seemed to be a bit hardier than the D9GKX in that they could consistently take more voltage and for longer than the slightly more fragile D9GKX.

Memory can also be binned according to a single chipset and as such can pull much greater performance on a given chipset compared to another. A great example of this is the Corsair Dominator PC2-10000 C5 modules, as they’re binned and tested specifically for the NVIDIA SLI chipsets (650i, 680i, 730i, 750i, 780i) and perform exceptionally well on that platform, as do the rest of the high-end Dominator kits. There are complications, though, such as being restricted to PC2-9600 or lower on other chipsets unless manually configured. That said, the Atomic labs’ Dominator PC2-10000 C5 are still the strongest kit of memory we’ve tested on any chipset, ranging from 680i to P965 to X38.

Another area we’ve not touched upon is bin overflow or ‘aggressive binning’, where the manufacturer bins for a speed level and then dumps all or part of that level down a grade to make an aggressive series or, as enthusiasts have found, an aggressive batch or batches. These aggressive batches are often the first runs of the product line and garner great initial coverage for the new modules. For the truly slimy, there were a number of brands releasing PC2-8500 C5 kits with Micron D9 based chips, to then a few months after release switched the ICs for the cheaper and less overclockable ProMOS chips.