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What I learned while optimizing my RAM timings for better PC performance
They may not always seem like it, but RAM timings are vital for good PC performance. RAM timings, also known as memory timings, control how quickly your memory can respond to a CPU request. Too fast, and you get data corruption. Too slow, and you get poor performance, long load times, and stuttering. There are four memory timing parameters: CAS Latency (tCL), Row Address to Column Address Delay (tRCD), Row Precharge Time (tRP), and Row Active Time (tRAS).
While there are important things to know about the different memory timing parameters, essentially, you always want to get a good balance between responsiveness and stability, so you don't want to max out your memory timings from the get-go. Of course, overclocking your RAM is a bit of a mystic art, but these few tips and tricks I've picked up over the years should help you get started.
Start with optimized settings like EXPO and XMP
They've been optimized for a reason and serve as a good baseline.
If you've never overclocked your computer's RAM before, a good place to start is the pre-optimized settings in your BIOS, which will be either EXPO or XMP (EXPO for AMD, XMP for Intel). These settings have been optimized for your hardware for good reason, and while they're never perfect, they can serve as a great baseline while tinkering when your memory clocks.
For some, loading the EXPO or XMP preset profiles may be as far as they want to go in adjusting memory timings, as AMD and Intel include EXPO and XMP memory profiles as part of the CPU warranty, but further overclocking will often void that protection, and if you make hasty adjustments, you can cook your components. The EXPO or XMP profiles will get you a pretty good amount of performance boost over the defaults, but your PC can do better if you're willing to do some additional research.
If you decide to push your PC's limits further, this is when you'll want to calculate the best possible timings for your particular build and do some manual tuning. And to start, you'll need some additional information on your RAM kit.
Either way, you should still make sure you do some thorough stress testing after applying the EXPO or XMP profile to ensure the stability of your PC build.
Research
Know your motherboard and RAM speed limits
Not every motherboard will be capable of utilizing the fastest RAM speeds, so you'll need to know your compatibility thresholds before you even start messing around with your BIOS settings. You'll also want to check your RAM kit's max frequency, as that will help determine latency. If you want a more reactive PC, you'll want RAM with a higher frequency. Assuming your motherboard can handle it.
If you don't know any of the timing or frequency information for your motherboard and RAM, you can find just about all of that info in Windows with a few software options, like ZenTimings for AMD or CPU-Z, which works with both Intel and AMD silicon. Your particular motherboard may also have software that will give you memory timing information from your board and RAM kit, so be sure to check your motherboard manufacturer's website for related tools.
Once you've got the software ready, you'll need to figure out your RAM kit's stock timings. Stock primary memory timings are provided by the RAM manufacturer (or viewed in ZenTimings or CPU-Z) as something like CL36-36-36. This gives you RAM timings in a particular order: tCL (CAS latency) - tRCD (Row Address to Column Address Delay) - tRP (Row Pre-charge Time). Occasionally, you'll also have a fourth primary timing listed, which is tRAS (Row Active Time), which would be written out as CL36-36-36-52.
You'll also want to figure out the manufacturer of your RAM kit's integrated circuit. Typically, this will be one of three brands: SK Hynix, Micron, or Samsung. While there are other RAM IC manufacturers, like Crucial, Kingston, and Cypress Semiconductor, most RAM kits tend to use circuits from Hynix, Micron, or Samsung. While you can overclock your RAM without knowing who made the IC, having that information can give you a general idea of what to expect.
How to find the best memory timings
Nanoseconds can make a huge difference
If you've never gotten this deep into overclocking your memory before, there are a few general rules to keep in mind: take things slow, thoroughly stress test your overclock settings in between adjustments, and get your PC to your personal optimized setup. While there are general golden rules for overclocking your PC, an overclock only makes sense if it works well for you personally.
While EXPO and XMP profiles are pretty generous for a lot of users, they won't take your PC to its full potential. Which is why you'll want to calculate the best memory timings yourself. If you're just starting out with adjusting memory timings for the first time, the GitHub MemTestHelper breakdown was written with DDR4 RAM in mind, but many of the same rules and advice apply for DDR5 RAM, since power management is the biggest change between memory standard generations. And that should get you caught up on what you'll need to know about how memory timings are calculated and how you'll want to balance your memory timings.
But if that's too much reading, essentially, you want a low CAS latency with a high frequency, though the exact best profiles may differ by RAM kit, since a higher frequency with a slightly higher CAS latency may end up evening out in terms of actual timings.
To calculate the exact cycle time of your memory, you just need to do some simple math: 2000 x Timing / DDR Frequency. So for a kit of DDR5-6000 CL36, you'd get: 2000 x 36 / 6000 = 12 nanoseconds (ns). While that's pretty fast, we can do better.
Which is where manual tuning comes in.
Manually adjusting your memory frequency
Small steps will get you the best results.
To manually overclock your memory timings, you'll return to your BIOS settings to adjust your frequency, BCLK/DRAM ratio, and memory controller gear setting.
When manually overclocking your memory timings, you'll want to increase your max frequency while also getting the lowest CAS latency you can for overall lower timings. To start, you'll want to adjust your frequency by 200 MHz above the XMP or EXPO profile. Thus, if the overclock profile frequency is 6400, you'd want to start with a frequency of 6600.
You then need to set your BCLK/DRAM ratio: either 100:100 or 100:133. While some older architectures benefit from the 133 DRAM ratio, it's generally best to start with 100:100, especially if you're new to overclocking RAM. You'll also want to choose the right gear setting, either G2 or G4. G2 sets the memory controller frequency to exactly half of the DRAM frequency, while G4 sets it to one quarter. For DDR5 RAM, you don't typically need the benefit of running the memory controller at such a low speed, so G2 is generally preferable.
So your first manual adjustment would be: 6600 (66 x 100.00 x 100.00) G2. You'll apply this setting in the BIOS, restart the PC, enter the OS, and run some memory stability tests to ensure your overclock is stable. If everything's still working, adjust to the next highest frequency until the system is no longer stable.
Once your system starts to struggle with your RAM speed, you'll want to add some voltage to the memory modules. This is where things get a bit dicey on the heating front, so if you want to drop back down to the last stable frequency and call it a day, that's entirely fair, especially for those new to overclocking. For Micron RAM kits, you'll usually top out at around 5400-5600 MHz, while SK Hynix and Samsung usually top out around 6000-6600 MHz. This is generally going to be higher than what your RAM kit was doing by default or with the XMP and EXPO profile, so it's a successful overclock.
But we can do better still.
Fine-tuning your timings
Apply additional voltage and adjust your core timings.
Adjusting your voltage offset comes with an additional risk of overheating your PC and potentially damaging some of your silicon. So there are a few things to keep in mind when adjusting your voltage so you don't cook your CPU or RAM into an unusable wafer.
There are five different voltage levels that impact overclocking capabilities, from CPU SA Voltage to DRAM VDDQ voltage. While there are no hard and fast limits, you don't really want your CPU SA Voltage to run higher than 1.35V, and you want to keep your DRAM VDDQ voltage at 1.4V or below. You may want to create a custom profile for this memory overclock, since these voltages are a bit too high for regular PC usage and should only be engaged when you're rendering video or gaming.
Alternatively, you can also under-volt your PC at this point. Drop your voltage down to where your PC becomes unstable, and then go back to the last stable voltage to have a more efficient PC with better RAM frequency.
You're then going to find the right balance of voltage and frequency to get the fastest memory speeds possible. Which brings us into primary, secondary, and tertiary timing adjustments. Again, you're going to make small adjustments until the system is unstable, and then dial the speeds back to the last stable setting. Essentially, you'll drop one timing down by 2, stress test your machine, and repeat the process until you get the lowest possible stable timing for your tCL, tRCD, and tRP. But there are a few general ranges we expect based on your RAM's IC:
As for your secondary and tertiary timings, some of them are well worth tweaking. Some will absolutely tank your system with even a small adjustment, so do keep these ranges in mind:
If this looks incomprehensible to you, I can break it down into a few easy categories to remember. tWR should match your tRAS primary timing. You want tFAW, tRDRD_dg, and tWRWR_dg set as low as possible, and both tRDRD_dg and tWRWR_dg should be set to 8 if possible. tREFI should be set as high as you can get it.
And if you set tRFC2 and tRFCpb too low, it will limit your top-end frequency. So that will probably be the most painstaking balancing act.
Final steps
Once you're happy with your RAM timings, there's just a bit left to do.
Once you've got your RAM timings where you want them, make sure you've adjusted your voltage back down slowly so you get the most efficient power profile for your RAM overclock if you have not done so already. While you could leave the voltage offset tuned high, generally, you don't want it to be higher than your build needs for stability and performance, so be sure to tighten things up before you call your overclock venture a success. Alternatively, create a new profile for these adjusted timings and enable it only when you need the extra performance, so you aren't constantly running your PC at an overvolted rate.
Of course, if you're planning to sync your RAM clock with your MCLK or FCLK, or go into precision boost optimization or curve optimization, don't adjust your offset back down just yet. You may need that extra voltage overhead while syncing your RAM timings with the rest of your overclock and optimization settings.
Alternatively, if you've gone for a more eco-friendly PC build, you may need to raise it back up if you plan to make any additional adjustments to MCLK or FCLK.