Due to anomalies in reporting software as well as system and configuration limitations, new memory may not function at full speeds or may report what appears to be lower performance than expected. There are several reasons for these issues, some of which are simply misunderstandings in how DRAM operates and others which can be overcome or offset by changes to your configuration.
A memory diagnostic tool is showing my memory as running half as fast as it should
Modern DRAM modules support double data rate (DDR) transfers, meaning that although they function at a given clock speed, they transfer data during both the rise and fall of a CPU clock cycle, allowing for double the data transfers their native speed, or frequency, would suggest. Some diagnostic or system information software does not express this clearly, only reflecting the modules' frequency in megahertz (MHz), making such feedback suggest that your parts are only running at half their possible speed. For example, DDR3-1600 supports 1600 megatransfers per second (MT/s) due to its nature as DDR memory, but runs at 800 MHz.
OurM.O.D. Utility (DDR3 version, DDR4 version), shown above, expresses speeds using both MHz and MT values when the module reports this data.
The memory is not running at its full speed
Another factor in this reporting comes from your system's CPU and motherboard. One of these components (typically the CPU in mainstream hardware) will feature a memory controller which may only offer support for a particular maximum frequency of memory, and as a result can bottleneck your module performance. To verify what your other hardware will natively support in terms of DRAM speeds, refer to both your CPU and motherboard specifications.
This factor can be compounded by the MHz/MT reporting differences. A DDR3-1600 module in an environment capping its performance at DDR3-1333 speed may report 667 MHz during diagnostics under these conditions.
Benefits of dual-, tri- and multi-channel memory
Also, multi-channel support from your system's motherboard results in additional performance above the installed memory's individual part capabilities. A dual-channel configuration using two identical DDR3-1600 parts effectively doubles their bandwidth, resulting in performance approaching 3200 MT/s. At this level, however, practical gains are not always easy to notice, and in some cases, simply increasing your memory total (for example adding a single 8GB part alongside an already installed 2GB module) may be most of the benefit you will receive from a given upgrade. We offer our parts inguaranteed-matching kitsto assist in taking full advantage of this feature in systems which support it.