Technical Article—Can Different DRAMs be Mixed?

Computer DIY users often encounter a situation: they want to replace a new DRAM module, but they may have another DRAM and worry that the two are incompatible. So, can DRAMs of different generations, speeds, delays, voltages or manufacturers be mixed and matched? Crucial, a brand of Micron, one of the world's largest memory manufacturers, has 24 years of advanced experience in memory and storage. The following are suggestions from Crucial experts on the above issues:

Factors to consider

Before we delve into what happens when you mix different types of memory, we should first look at what exactly differentiates different DRAM modules. Generally speaking, DRAM is determined by the following five factors:

1. Generation: This refers to the version of DRAM chips. Each generation of DRAM has improvements in speed, latency, voltage, etc.

2. Speed: This is how quickly the computer can store and retrieve data from the memory module. Generally speaking, the faster the DRAM, the better.

3. Latency: Also known as “timing,” this refers to the number of clock cycles required for the system’s CPU to complete a read/write task. The lower the latency of a DRAM module, the less time it takes to complete these tasks.

4. Voltage: This is related to the power consumed by the DRAM module.

5. Brand: The memory manufacturer and/or assembler, such as Crucial.

Can different versions of DRAM be mixed?

Assuming there is legacy DDR3 RAM in the system, can a DDR4 module be installed alongside the DDR3 to achieve better performance?

Experts advise against trying this; different versions of DRAM cannot be mixed.

In fact, users can't install another version of DRAM in their system at all. The reason is that a computer's motherboard can only handle a certain generation of memory, and the pin locations are different for each generation of DRAM, which prevents users from accidentally installing the wrong module.

Can DRAMs of different speeds, latencies, and voltages be mixed?

If you want to install DRAM modules of different speeds, while it is technically possible, there is one important thing to note: the DRAM will run at the speed of the slowest module. For example, if you have a DDR3 1333MHz system and install a second module at 1600MHz, they will both run at 1333MHz.

The same thing happens with modules with different latencies. The system will run based on the module with the slowest timing. Also pay attention to what speeds the motherboard can handle. If the motherboard can only handle 1333MHz modules, then a 1600MHz module will only run at 1333MHz.

What about DRAM modules with different voltages? The situation is that both modules will run at the higher voltage.

For example, if you have a 1.5v module in one slot and a dual voltage (1.35v/1.5v) model in the other slot, the system will run at 1.5v. If you want your DRAM modules to run at 1.35v, all modules must be 1.35v, and the motherboard must support the lower voltage.

So, the result is that DRAMs of different speeds, latencies, and voltages can be mixed and matched, but the more efficient modules cannot take advantage of their benefits. If you can afford to replace all modules with faster, lower latency modules, you will get the most benefit. If you want to save money, you can buy other modules of the same speed and latency to get the best value.

Users experienced in overclocking can adjust BIOS and other settings to improve the performance of mixed-speed modules. However, this may lead to unpredictable results.

Can different brands of DRAM be mixed?

We have already made it clear that you cannot mix different versions of DRAM. Moreover, mixing modules with different speeds, delays, or voltages is not the best choice. So, what happens when you mix different brands of DRAM?

In theory, there should be no problem using two different brands of DRAM if the other characteristics (generation, speed, latency, voltage) are the same, but some older DDR3 systems require matching sets of memory.

Keep in mind that many memory brands don't make their own DRAM; they just assemble the modules. There are only a handful of true memory manufacturers.

Slight variations in the assembly process, not to mention differences between manufacturers, can affect module performance, and although the odds are slim, there are always cases where modules don't work together and your system blue screens.

Therefore, users are advised to carefully review the manufacturer's documentation and be prepared to take risks.

Summarize

This article discusses various scenarios for mixing and matching different DRAM modules, and the problems that can arise. In general, the simplest solution is to avoid mixing DRAM altogether. Memory is so cheap these days that there's no need to risk the hassle of dealing with incompatible modules.