Every program on your PC churns through RAM as it works. Your RAM operates at a certain speed set in place by the manufacturer, but a few minutes in the BIOS can bump it up far beyond its rated specification.
Yes, RAM Speed Matters
Every program you run gets loaded into RAM from your SSD or hard drive, which are comparatively much slower. Once it’s loaded, it usually stays there for a while, being accessed by the CPU whenever it needs it.
Improving the speed at which your RAM runs can directly improve your CPU’s performance in certain situations, though there is a point of diminishing returns when the CPU simply can’t churn through more memory fast enough. In day-to-day tasks, the RAM being a few nanoseconds faster might not matter, but if you’re really crunching numbers, any small performance improvement can help.
In games though, RAM speed can actually have a noticeable effect. Each frame might only have a few milliseconds to process a lot of data, so if the game you’re playing is CPU bound (like CSGO), faster RAM can improve framerates. Take a look at this benchmark from Linus Tech Tips:
The average frame rate is usually boosted a few percentage points with faster RAM when the CPU is doing most of the work. Where RAM speed really shines is in minimum framerates; for example, when you load a new area or new objects in a game, if it all has to happen in one frame, that frame could take longer than usual if it’s waiting on the memory to load. This is called microstuttering, and it can make games feel choppy even when the average frame rate is high.
Overclocking RAM Isn’t Scary
Overclocking RAM isn’t nearly as scary or unsafe as overclocking a CPU or GPU. When you overclock a CPU, you have to worry about whether or not your cooling will handle the faster clocks. An overclocked CPU or GPU can be much louder than one running at stock settings.
With memory, they don’t produce much heat at all, so it’s quite safe. Even on unstable overclocks, the worst that happens is you’ll get an error when testing for stability and be kicked back to the drawing board. Though if you’re trying this on a laptop, you’ll want to verify that you’re able to clear CMOS (to reset the BIOS to default settings) if something does go wrong.
Speed, Timings, and CAS Latency
RAM speed is generally measured in megahertz, usually abbreviated as “Mhz.” This is a measure of the clock speed (how many times per second the RAM can access its memory) and is the same way CPU speed is measured. The “stock” speed for DDR4 (the newest memory type) is usually 2133 Mhz or 2400 Mhz. Though this is actually a bit of a marketing lie; DDR stands for “Double Data Rate,” meaning the RAM reads and writes twice for every clock cycle. So really, the speed is 1200 Mhz, or 2400 mega-ticks per second.
But most DDR4 RAM is usually 3000 Mhz, 3200 Mhz, or higher. This is because of XMP (Extreme Memory Profile). XMP is essentially the RAM telling the system, “Hey, I know DDR4 is only supposed to support speeds up to 2666 Mhz, but why don’t you go ahead and overclock me to the speed on the box?” It’s an overclock from the factory, already pre-tuned, tested, and ready to go. It accomplishes this at the hardware level with a chip on the RAM itself called a serial presence detect chip, so there’s only ever one XMP profile per stick:
Every kit of RAM actually has multiple speeds baked into it; the stock speeds use the same presence detection system, and are called JEDEC. Anything higher than the stock JEDEC speeds is an overclock, meaning XMP is simply a JEDEC profile that has been overclocked by the factory.
RAM timings and CAS latency are a different measure of speed. They are a measure of latency (how fast your RAM responds). CAS latency is a measure of how many clock cycles there are between the READ command being sent to the memory stick and the CPU getting a response back. It’s usually referred to as “CL” after the RAM speed, for instance, “3200 Mhz CL16.”
This is usually tied to the RAM speed—higher speed, higher CAS latency. But CAS latency is only one of many different timings and clocks that make RAM work; the rest are generally just referred to as “RAM timings.” The lower and tighter the timings are, the faster your RAM will be. If you want to learn more about what each timing really means, you can read this guide from Gamers Nexus.
XMP Won’t Do It All for You
You may buy your RAM from G.Skill, Crucial, or Corsair, but those companies don’t make the actual DDR4 memory chips that make your RAM tick. They buy those from semiconductor foundries, which means all the RAM on the market comes from a few main places only: Samsung, Micron, and Hynix.
Additionally, the flashy kits of memory that are rated for 4000+ Mhz at low CAS latencies are the same thing as the “slow” memory that cost half the price. They’re both using Samsung B-die DDR4 memory chips, except one has a gold colored heat spreader, RGB lights, and a bejeweled top (yes this is a real thing you can buy).
When the chips come from the factory, they’re tested in a process called binning. Not all RAM performs the best. Some RAM handles itself really well at 4000+ Mhz with low CAS latency, and some RAM can’t overclock past 3000 Mhz. It’s called the silicon lottery, and it’s what makes high speed kits expensive.
But the speed on the box doesn’t always match up with your RAM’s true potential. The XMP speed is just a rating that guarantees that stick of memory will perform at the rated speed 100% of the time. It’s more about marketing and product segmentation than it is about the limits of the RAM; nothing prevents your RAM from operating outside of the manufacturer’s spec, other than that enabling XMP is easier than overclocking it yourself.
XMP is also limited to a few specific timings. According to a representative at Kingston, they “tune the ‘Primary’ timings (CL,RCD,RP,RAS) only,” and since the SPD system used to store XMP profiles has a limited set of entries, the rest is up to the motherboard to decide, which doesn’t always make the right choice. In my case, my ASUS motherboard’s “auto” settings set some extremely strange values for some of the timings. My kit of RAM refused to run with the XMP profile out of the box until I fixed the timings myself.
Additionally, the factory binning process will have a set voltage range they want to operate in. For example, they may bin their kits of RAM at 1.35 volts, not do extended testing if it doesn’t pass, and chuck it in the “3200 Mhz mid-tier bin” that most kits of memory fall into. But what if you ran the memory at 1.375 volts? What about 1.390 volts? Both are still nowhere close to unsafe voltages for DDR4, and even just a little bit of extra voltage can help the memory clock much higher.
How To Overclock Your RAM
The hardest part of overclocking RAM is finding out what speed and timings you should use because the BIOS has more than 30 separate settings for you to tweak. Luckily, only four of them are considered ‘Primary’ timings, and you can calculate them with a tool called “Ryzen DRAM Calculator.” It’s tailored to AMD systems, but it will still work for Intel users as it’s largely about the memory timings, not the CPU.
Download the tool and fill in your RAM speed and what type you have (if you don’t know, a quick Google search for your RAM’s part number should bring up some results). Press the purple “R – XMP” button to load your kit’s rated specs, and then press “Calculate SAFE” or “Calculate FAST” to view your new timings.
You can compare these timings with the rated specs using the “compare timings” button, and you’ll find that everything is tightened up a bit on the SAFE settings, and the primary CAS latency is reduced on the FAST settings. It’s hit or miss whether the FAST settings will work well for you, as it depends on the kit coming with a loose bin from the factory, but you can likely get it working on a safe voltage range.
You’ll want to send a screenshot of this to another device because you’ll need to enter these timings in the BIOS. Then, once you get it working, you’ll need to verify the overclock is stable using the calculator’s built-in memory tester. This is a bit of a long process, so you can read our guide to overclocking your RAM to learn more about it.
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