Generation Differences


Adata XPG Spectrix RGB LED 2x8GB Kit 3000MHz PC4-24000 DDR4

When looking at buying RAM one of the first things you may come across is DDR3 and DDR4. This represents which generation of RAM it is, with DDR4 being the most recent generation of RAM.

The two biggest drivers of speed for a PC are storage and RAM. More RAM improves PC performance, not just for hardcore applications like games but also more common apps like web browsers. DDR3 was a giant leap over its predecessor DDR2, and this comparison looks at whether that is true for DDR4 as well.

The DDR4 standard offers higher module density, better reliability, higher transfer rates and decreased voltage thereby providing increased speed and better power efficiency. It is also a standard designed with the future in mind; e.g., it supports 3D stacking of dies with through-silicon-vias (TSVs) which allows increasing module density by stacking up to 8 dies. But in practice users may not experience a noticeable difference in performance when using DDR4 RAM modules available today.

DDR4 is not backward compatible with DDR3 motherboards because the physical design of modules (DIMMs) for DDR4 and DDR3 are different.

DDR4 vs DDR3 DIMMs

DDR3 modules use 240 pins and DDR4 DIMMs use 288 pins. Both DDR3 and DDR4 DIMMs are 5¼ inch (133.35 mm) in length but the pins in DDR4 are spaced closer (0.85mm) than DDR4 (1mm).

They are also different in height and thickness — the increased height of DDR4 modules (31.25mm instead of DDR3’s 30.35mm) makes signal routing easier, and the increased thickness (1.2mm vs. DDR3’s 1mm) accommodates more signal layers.

The position of the notch on DDR4 memory modules is also different from DDR3 modules. This prevents accidental insertion of the wrong type of memory because they are not backward compatible.

Cost and Market Share

DDR4 adoption has been much slower than DDR3. Prices for DDR4 memory modules have not fallen with mass adoption, so the DIMMs continue to be more expensive compared with DDR3 modules. Search trends also reveal that as of August 2017, DDR3 memory continues to be more popular worldwide.

DDR3 or DDR4: Which one should I choose?

For most consumers the choice will be simple because DDR4 is not backward compatible. If your motherboard was designed for DDR3, then that’s what you can choose. Even if you’re setting up a new PC, you will still choose based on the other components — the CPU and motherboard — of the system.

Some of the latest CPUs from both Intel and AMD support DDR4 SDRAM and some are still designed for DDR3. DDR4 would have been a good way to future-proof a new PC but chances are DDR3 will continue to be in wide use for the next 3-5 years at least. And future gains in DDR4 performance probably won’t benefit current systems because the clock speeds won’t match.

Speed

When buying RAM you’ll see these large numbers followed by MHz (Megahertz). You probably already know this represents the speed, at least in part, but what does RAM speed actually even do for your computer? Faster RAM speeds allow your processor to access the data stored on it quicker, giving your system a boost in processor performance.

Clock Cycles (RAM MHz)

RAM frequency works off of clock cycles (note: people often call this the RAM speed even though it is really only part of the speed equation). Each read and write is done on a cycle. RAM is measured by how many cycles per second it can perform. For example, if RAM is rated at 3200 MHz, it performs 3200 cycles per second.

The more of these cycles that happen per second, the more data can be stored and read, making for a smoother user experience.

CAS Latency

Column Access Strobe (CAS) latency, or CL, is the delay time of your RAM receiving a command and then being able to issue it. The numbers for the timings will look something like this 15-17-17-35. Those numbers indicate how many clock cycles it takes for the RAM to respond to the command.

Because the timings determine how fast your RAM will respond to a command. As such, faster MHz RAM with slower CAS timings might not be better than slower MHz RAM with faster CAS timings.

Finding Your REAL RAM Speed

In order to find the real speed of your RAM, you want to take the frequency of your RAM (let’s say it’s 3200 MHz), and divide it by the first number listed for the CAS timings, let’s say 14.

So that gives us 3200/14 = 228.58. This gives us how many instructions per second the RAM can carry out.

Now, let’s compare it to slower MHz RAM with a lower CAS timing.

We’ll use 2133 MHz RAM using a CAS latency of 6.

2133/6=355.5. This means that 2133 MHz RAM with a CAS latency of 6 will actually respond 55% faster!

RAM Speed for Gaming Performance

Even with as little as 8GB of RAM running at stock clock speeds, there’s no difference in performance, at least as far as graphics are concerned. In fact, despite the RAM speed difference, there is no significant impact on graphics, just CPU tests.

This is because programs like games (with a few exceptions here and there) are more graphics intensive than anything else, and will require more work from your video card (and its built-in RAM) and processor than your RAM.

Where you will see major RAM speeds actually benefit you is when you’re doing multitasking like running multiple programs, or streaming while you game and even content creation.

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