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Table of Contents
- Introduction
- About Memory Overclocking
- How to Choose a Memory Kit
- What is XMP?
- SPD vs XMP
- Additional Notes on SPD
- Verify Memory Speed with CPU-Z
Introduction
Overclocking is considered to be an art form by many PC enthusiasts, since it takes into account many aspects of hardware knowledge. So while overclocking can be complex, memory overclocking has been simplified over the years to allow novices and general DIY PC builders achieve a reasonable level of memory overclock with compatible CPUs and motherboards. XMP is one such technology.
If you just want to find out how to enable XMP, click here to read about "How to Enable XMP".
About Memory Overclocking
Memory overclocking can be an effective way to increase PC performance, through increasing the frequency speed or decreasing the latency timing of the memory. However, since PC memory operates closely with the CPU and motherboard, the result of memory overclocking will vary and is interdependent with the capability of the CPU and motherboard.
Therefore, it is important to check the QVL (Qualified Vendor List) for your G.SKILL memory kit to find a compatible motherboard model before purchasing the memory kit.
PC memory is also controlled by the IMC (integrated memory controller) within the CPU, so the CPU IMC also needs to be strong enough to support the overclocked speed of the memory, and not all IMC of the same CPU model are equal in strength. So some extremely high speed memory kits are designed for extreme overclockers, which requires CPUs with strong IMC and overclock-oriented motherboards to be able to run at the rated specification.
How to Choose a Memory Kit
If you have already chosen a CPU and motherboard, then you can email our technical support team for a G.SKILL memory kit recommendation. It would also help us narrow down our recommendations if you include the total memory capacity you are looking for in the email.
What is XMP?
XMP stands for "Extreme Memory Profile" and was first introduced by Intel in 2007 with DDR3 memory. Later, Intel XMP was updated to Intel XMP 2.0 for DDR4 memory, and Intel XMP 3.0 for DDR5 memory. The introduction of XMP greatly simplified the process of memory overclocking.
XMP contains memory settings to help the motherboard BIOS overclock the installed memory kit. While there are many settings and values that are related to memory, the most important ones include memory speed, latency timings, and memory voltage. When XMP is enabled in the BIOS, the system would load these memory settings in the BIOS and then use these settings to start up the system on the next boot. It's important to note that the motherboard BIOS determines which settings to load from the XMP profile, and can choose to override certain XMP settings.
For G.SKILL memory kits with XMP support, the included XMP profile is intended for use with a single memory kit, so if multiple memory kits are installed in the same system or on the same motherboard, then the XMP settings might not work properly.
SPD vs XMP
In a newly built PC system, the motherboard would read the SPD profile from the memory module, and boot the system using these memory settings by default. In most cases, SPD profiles contain default standard memory settings, which are defined by the JEDEC organization, so PC memory conforming to the JEDEC standard can boot on any supported motherboard by default. For example, it would be expected for a standard DDR4 memory kit to function properly on any motherboard that supports DDR4 memory.
In other words, all PC memory comes with SPD profiles. On the other hand, XMP is only included on high-performance overclock memory kits.
For each DDR memory generation, there are many sets of memory specifications defined by the JEDEC standard. Below are some common standard JEDEC specifications:
DDR3-1066 CL7-7-7 @ 1.5V
DDR3-1333 CL9-9-9 @ 1.5V
DDR3-1600 CL11-11-11 @ 1.5V
DDR4-2133 CL15-15-15 @ 1.2V
DDR4-2400 CL17-17-17 @ 1.2V
DDR4-2666 CL19-19-19 @ 1.2V
DDR4-3200 CL22-22-22 @ 1.2V
DDR5-4800 CL40-40-40 @ 1.1V
The above list is not exhaustive, but gives an idea of what standard memory specification looks like. So if you see "SPD speed" or "SPD specification", it refers to one of the standard JEDEC specifications.
Memory specifications of high-performance overclocked memory with XMP support typically have different memory speed, latency timing, and/or memory voltage settings than standard JEDEC specifications, such as DDR4-2400 CL15-15-15 @ 1.2V or DDR4-3200 CL14-14-14 @ 1.35V. To configure the system to operate at XMP memory specifications, enabling XMP in the BIOS is required.
Additional Notes on SPD
SPD stands for "Serial Presence Detect". It originally refers to the EEPROM chip on the memory module that stores the default memory settings, so the motherboard would be able to detect the memory module and know what settings to use for the memory module to function with the system. In this case, the chip is referred to as the "SPD chip". Later on, the default memory settings stored on this chip was referred to as the "SPD profile".
The support for maximum default SPD memory speed may also vary, depending on the CPU and chipset combinations. For example, if we don’t consider memory overclocking or XMP support, the following CPU and chipset combinations would result in different maximum default SPD memory speeds, even if these CPUs and chipsets are from the same hardware generation:
Intel Core i3-9300 + Z370 Chipset = DDR4-2400
Intel Core i5-9600 + Z370 Chipset = DDR4-2666
Intel Core i3-9300 + H370/B360 Chipset = DDR4-2400
Intel Core i5-9600 + H370/B360 Chipset = DDR4-2666
It can be seen that if a standard DDR4-2666 memory kit is used with an Intel Core i3-9300 processor and a H370/B360 chipset motherboard, the resulting memory speed would be limited to DDR4-2400. Therefore, it is important to review the CPU and motherboard chipset specifications before choosing a memory kit.
Verify Memory Speed with CPU-Z
After booting into Windows, you can use the free CPU-Z application to check the operating memory frequency. If the operating memory frequency matches the XMP speed of the memory kit, then XMP is successfully enabled.
In CPU-Z, go to the "Memory" tab and find "DRAM Frequency". Then multiple this value by 2 to get the operating DDR transfer rate, which should match the memory kit specifications. In the example above, "DRAM Frequency" shows "1600", and multiplying this by 2 would result in "3200", which matches the correct "DDR4-3200" specification of this memory kit.