RAM:Why won't my old high-end kit work at its rated speed on a new motherboard, or vice versa?

For DDR5 owners:

As DDR5 is still an early platform, please keep in mind the following when considering issues with achieving rated speeds:

Stability with XMP: High-frequency DDR5 RAM, when operated with XMP (Extreme Memory Profile) settings, can sometimes be unstable. This is partly due to the high voltages and tight timings required to run at these speeds. For instance, achieving stability at 7200MHz often requires manual tweaking of timings and voltages, which can be a complex and requires advanced knowledge. One way to navigate issues with stability on higher frequencies is to loosen timings to achieve stability at high frequencies​.

Mixing Memory Kits: Mixing different DDR5 RAM kits, even if they're of the same speed and CAS latency, can lead to issues. This is because each kit is tested to work as a pair, and mixing two pairs, even of the same set, may result in inefficiencies or compatibility issues. This is especially true at higher speeds, where the memory controller of the CPU can be a limiting factor. For instance, while a motherboard may support up to 7800MHz, the actual achievable speed can be capped by the memory controller on the CPU, which might not reliably handle such high frequencies, particularly with four DIMMs or two dual-rank DIMMs​​.

DDR5 Specifications and Timings: DDR5 memory comes with various JEDEC standards ranging from DDR5-4800 to DDR5-6400, and there are placeholders for even higher speeds like DDR5-8000. However, the specifics of these standards, especially at the higher end, are still evolving.

BIOS updates: As DDR5 is still in it's infancy, its important to keep track of your motherboard's BIOS updates as manufacturers have been improving and releasing updated BIOS to help improve stability while XMP is enabled.

For DDR4 owners:

Memory kits are designed around the motherboards available at the time. This means a high-end kit from a few years ago may not work as intended on a recently released motherboard, as the new motherboard was not designed to handle how the older memory kit was made.

This issue is mostly present in kits meant for Z170 and X99, and were likely purchased in or before 2017. For example, our VENGEANCE LPX 16GB DDR4 2800MHz memory kit is a kit from around 2017 and has no support for AMD chipsets.

This also applies to trying to use a new high-end memory kit on an older motherboard. Because the new kits are designed for newer generation motherboards, older motherboards may run into compatibility issues even if the motherboards state support for the rated speed.

For example, our VENGEANCE LPX 16GB DDR4 3600MHz memory kit states support for Intel 300 series and above, along with only X570 for AMD. Some B450, X470, Z170, and Z270 motherboards state support for 3600MHz, but that does not mean they are able to run our kit as intended.

If you are having issues getting your memory kit to run at its rated speed, take a look at our help article on the subject for further troubleshooting.