Content of the material
- What Is RAM?
- Primary vs Secondary Memory
- RAM Brands
- Graphics Double Data Rate Synchronous Dynamic RAM (GDDR SDRAM)
- How to Minimize the Performance Loss When Pairing Ram of Different Size Clock Speed
- Can You Mix Different RAM Voltages?
- Can you mix DDR3 and DDR4 RAM?
- Can you mix different RAM Frequencies?
- Can you mix RAM Modules with different sizes?
- Understanding RAM Specifications
- 1. Memory Form Factor
- 2. Memory Type Or Generation
- 3. Memory Size
- 4. Memory Speed
- 5. Memory Latency
- 6. Memory Voltage
- 7. Memory Brand
- Planning Your Memory Configuration
- RAM Speed
- Recent Posts
What Is RAM?
RAM stands for Random Access Memory, and it gives computers the virtual space needed to manage information and solve problems in the moment. You can think of it as reusable scratch paper that you would write notes, numbers, or drawings on with a pencil. If you run out of room on the paper, you make more by erasing what you no longer need; RAM behaves similarly when it needs more space to deal with temporary information (i.e. running software/programs). Larger pieces of paper allow you to scribble out more (and bigger) ideas at a time before having to erase; more RAM inside of computers shares a similar effect.
RAM comes in a variety of shapes (i.e. the way it physically connects to or interfaces with computing systems), capacities (measured in MB or GB), speeds (measured in MHz or GHz), and architectures. These and other aspects are important to consider when upgrading systems with RAM, as computer systems (e.g. hardware, motherboards) have to adhere to strict compatibility guidelines. For example:
- Older-generation computers are unlikely to accommodate the more recent types of RAM technology
- Laptop memory won’t fit in desktops (and vice versa)
- RAM is not always backward compatible
- A system generally can't mix and match different types/generations of RAM together
Primary vs Secondary Memory
After talking about primary and secondary memory in detail, let’s finally look at their differences to help you understand better:
|Primary Memory||Secondary Memory|
|Nature||Can be volatile (RAM) and non-volatile (ROM)||Non-volatile|
|Alias||Internal memory||Auxiliary memory|
|Price||Typically more pricy than secondary memory||Cheaper than primary memory|
|Access||Accessed directly by processing unit||Accessed indirectly, need to be transferred to the primary memory before accessed by CPU|
|Accesses||Accessed by the data bus||Accessed by I/O channels|
|Formation||Volatile memory won’t retain data||Non-volatile memory will be able to retain data|
|Capacity||Usually smaller storage than secondary memory||Has much more power to store data|
In theory, two or more different manufacturers could manufacture the same RAM modules and sell them in slightly different packaging, and we’re sure that this is happening to some extent.
The problem is that RAM manufacturers advertise not all RAM specifications, let alone retailers. Even if you find two RAM modules with the same size, frequency, timings, and voltage, the actual memory and controller chips could be different, and the minute differences could manifest themselves as random freezes and crashes.
That’s why we recommend you avoid mixing RAM brands and sticking with just one manufacturer. If your manufacturer no longer sells the same RAM modules you have, consider looking for used ones on eBay or Craigslist.
Graphics Double Data Rate Synchronous Dynamic RAM (GDDR SDRAM)
- Time in market: 2003 to present
- Popular products using GDDR SDRAM: Video graphics cards, some tablets
GDDR SDRAM is a type of DDR SDRAM that is specifically designed for video graphics rendering, typically in conjunction with a dedicated GPU (graphics processing unit) on a video card. Modern PC games are known to push the envelope with incredibly realistic high-definition environments, often requiring hefty system specs and the best video card hardware in order to play (especially when using 720p or 1080p high-resolution displays).The 4 Best Graphics Cards of 2022
- Similar to DDR SDRAM, GDDR SDRAM has its own evolutionary line (improving performance and lowering power consumption): GDDR2 SDRAM, GDDR3 SDRAM, GDDR4 SDRAM, and GDDR5 SDRAM.
Despite sharing very similar characteristics with DDR SDRAM, GDDR SDRAM is not exactly the same. There are notable differences with the way GDDR SDRAM operates, particularly regarding how bandwidth is favored over latency. GDDR SDRAM is expected to process massive amounts of data (bandwidth), but not necessarily at the fastest speeds (latency); think of a 16-lane highway set at 55 MPH. Comparatively, DDR SDRAM is expected to have low latency to immediately respond to the CPU; think of a 2-lane highway set at 85 MPH.
How to Minimize the Performance Loss When Pairing Ram of Different Size Clock Speed
The only thing that can minimize the performance loss (not eliminating it) is the voltage. Now as you have ram modules with different brands and sizes, it’s better to find a sweet spot between both so that you get the most out of them.
Another factor to look for is the CAS Latency of your ram module. CAS or Column Address Strobe is related to the number of cycles it takes for a ram module to access in one of its columns.
Overall, it’s better if you look for CAS Latency and Voltage two different ram modules from the same brand. Ram modules from different brands can have a minute difference in CAS Latency and voltage even if they look similar.
Can You Mix Different RAM Voltages?
Different voltage requirements that two RAM sticks may have won’t prevent you from combining them, but it won’t create an optimal situation.
Two different RAM brands with different voltages will cause the motherboard to run with the lowest one by default, resulting in the more power-demanding RAM stick getting less voltage than necessary.
This issue won’t keep the RAM from operating, but it’ll prevent it from functioning at its full potential with its peak frequency and stability.
Can you mix DDR3 and DDR4 RAM?
No, you can’t mix RAM Modules from different generations. DDR3 and DDR4 RAM are physically incompatible.
Can you mix different RAM Frequencies?
You can mix RAM Modules with different frequencies, but it might turn out to be problematic. All RAM Modules have to always run at the same frequency, meaning they’ll try to run at the smallest common denominator.
Because different types of RAM modules support specific latencies at different frequencies, though, they might not be able to sync properly, causing stability issues, or preventing you from POSTing or booting your system entirely.
Can you mix RAM Modules with different sizes?
As long as the frequency, brand, latency, and ranks of your RAM modules match, mixing different RAM capacities should pose no issues in most cases.
Understanding RAM Specifications
To fully understand the answer to the big question about mixing RAMs, you need to know what specifications and features define a RAM.
If you’re already a pro in this area, skip this section and go straight to the answer.
1. Memory Form Factor
RAM modules are available in two primary and standard form factors:
- Dual In-Line Memory Module or DIMM: The DIMM is the RAM form factor used for desktop computers, and it refers to the physical size of the RAM stick, which is bigger for desktops. The standard length is 133.35 mm for DIMMs.
- Small Outline DIMM or SO-DIMM: SO-DIMM RAM modules are for laptops and compact computers in general. They’re almost half as small as DIMMs, at just 67.6 mm in length.
2. Memory Type Or Generation
As technology has evolved over the years, RAM sticks have also improved and gained more enhanced features and capabilities.
There are five main generations for the DDR SDRAMs (Double Data Rate Synchronous Dynamic RAM) that are commonly in use today:
- 2000 release: DDR1 SDRAM
- 2003 release: DDR2 SDRAM
- 2007 release: DDR3 SDRAM
- 2014 release: DDR4 SDRAM
- 2020 release: DDR5 SDRAM
There’s no backward or forward compatibility between these RAM generations, and you can’t fit one into a slot made for the other since they use a different number of pins.
3. Memory Size
RAM sizes refer to the capacity of each RAM stick and how much information it can store.
RAM modules come in different sizes, varying from 2GB to 32GB.
For instance, you can get two 4GB RAM sticks, so your computer has a total of 8 GB memory space.
4. Memory Speed
RAM speed or frequency is the number of cycles a RAM stick can perform every second.
The higher the RAM frequency, the more data your RAM can read and store, and the smoother your system will work.
RAM frequency is measured in megahertz (MHz), million cycles per second.
For example, if you see the number 3600MHz next to a RAM’s name, you’ll know that it can perform 3.6 billion cycles per second.
That means the RAM stick can transfer that many bits in one second!
5. Memory Latency
Latency is the amount of time it takes a memory module to respond to a call or command your system gives by accessing a specific set of data in one of its columns.
You’ll see the letters “CL” next to a number in a RAM’s specifications, indicating its latency.
For instance, a CL16 RAM stick will take 16 cycles to respond to a command.
The lower the latency, the faster your RAM will be.
6. Memory Voltage
The power that the DRAM modules consume is referred to as their voltage.
Different RAM types and models have different voltages ranging from 1 V to 1.4 V.
You can make your RAM run at different voltages to adjust performance and stability, but it’s not recommended to overclock it more than 1.5 V.
7. Memory Brand
Different manufacturers or assemblers are making RAM sticks and putting them up for purchase, and each has a different brand name.
It’s a known fact that two different manufacturers can make the same RAM sticks and sell them in slightly different packaging.
However, you can never be sure since they never publicize all RAM specs or retailers.
You could find two RAM modules with the same type, size, frequency, latency, and voltage, but the memory and controller chips could end up being different.
Planning Your Memory Configuration
Depending on the manufacturer of your CPU, the optimal specifications will differ.
If you are wondering how much memory you should purchase, it will depend on the workload you wish to accommodate.
For video editing, for example, 32 to 64 GB of RAM is recommended, while for gaming 16 GB will suffice.
For AMD processors, the best RAM speed to aim for will be double the internal frequency of the Infinity Fabric – also known as FCLK or Fclock. This double data rate will assure a level of synchronicity between your CPU and RAM that will achieve optimal performance.
For Zen 2 and Zen 3 CPUs, the FCLK is 1,800 MHz; so a 3,600 MHz CL 16 RAM kit is a future-proof speed metric.
This kit speed has proven to provide better performance than a 3,200 MHz CL 14 kit, despite having a larger absolute latency metric (8.89 ns vs 8.75 ns).
Do note that the FCLK value can be overclocked; so if your workload requires faster frequencies, you can purchase kits that have a double-data-rate frequency of the overclocked FCLK value.
For a full breakdown of the best memory for AMD CPUs, check our relevant article.
Also, it must be noted that Samsung’s B-Die has been proven to be the best RAM-die for AMD processors.
Purchasing RAM sticks for an Intel CPU is also quite simple, as they have been benchmarked and factory-tested at a specific RAM kit speed: 3,200 MHz CL 14.
These specifications are in accordance with Intel’s internal testing, so it is safe to label this speed as the sweet spot for Intel CPUs.
RAM speed boils down to two specifications: RAM frequency and CAS latency. Here’s a popular RAM kit from a well-known manufacturer:
HyperX Fury Black 32GB (2x16GB) DDR4 3200 CL16
RAM frequency is the second to last number (3200 MHz), while CAS latency is the last specification (CL16). But what do they mean?
Well, RAM frequency is the number of cycles a RAM module can perform each second. So, the HyperX Fury Black kit can perform 3.2 billion cycles per second. Generally, the more cycles per second a RAM module can perform, the faster it is.
CAS latency is the amount of time it takes a RAM module to respond to a command. A RAM kit with a CAS latency of 16 takes 16 cycles to respond to a command, while a RAM kit with a CAS of 8 takes just 8 cycles.
Sometimes a RAM module with a lower frequency but a very fast response time perform better than a high-frequency module with a very high CAS.
When you mix RAM modules with different speeds, your computer will most likely run just fine, but it will perform to the speed of the slower RAM module by adjusting its frequency, timing, and voltage.
What’s even worse is that you may encounter random stability issues, which are almost always extremely difficult to troubleshoot and fix without replacing the mismatched module for a matching one.
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