Memory timings explained: CL16 vs CL18 vs CL22 in 2026

Every stick of DDR4 and DDR5 memory carries primary timings on the label. The first and most quoted is CAS latency: CL16, CL18, CL22 and so on. Buyers assume lower is always better, and either overspend on a kit that does not help their workload, or leave performance on the table. This piece explains what CAS latency measures, and what it means at 1080p and 1440p in 2026.

What CAS latency actually measures

CAS latency is the delay, in memory clock cycles, between the controller asking for a column of data and the memory returning it. A CL16 kit takes 16 cycles, a CL22 kit takes 22. That sounds huge, but a cycle at DDR4 3600 lasts about 0.556 ns, while a cycle at DDR4 2666 lasts about 0.75 ns. What you care about is true latency in nanoseconds: CL divided by half the data rate, multiplied by 1000.

Worked examples for common 2026 kits:

• DDR4 3600 CL16: 8.89 ns
• DDR4 3200 CL16: 10.00 ns
• DDR4 3200 CL18: 11.25 ns
• DDR4 2666 CL19: 14.25 ns
• DDR5 6000 CL30: 10.00 ns
• DDR5 5600 CL46: 16.43 ns

DDR4 3600 CL16 and DDR5 6000 CL30 sit within touching distance on true latency, which is why DDR4 3600 CL16 remains a serious performer on AM4 and older Intel platforms.

Frequency versus timings

Higher frequency means more transfers per second. Tighter timings mean each transfer arrives sooner. Games (especially CPU bound scenes) care about both, with a bias toward latency. Content creation that streams large blocks (video encoding, compilation, 7 Zip) leans on raw bandwidth.

On Ryzen 3000 and 5000 series, DDR4 3600 CL16 has been the sweet spot for years, because Infinity Fabric runs 1:1 with the memory controller at 1800 MHz. Pushing higher forces a decoupled ratio that hurts more than it helps. On DDR5, 6000 CL30 (AM5) or 6400 CL32 (Intel LGA 1700 and 1851) are the reliable sweet spots.

Real world FPS impact at 1080p

At 1080p with a strong GPU, the CPU and memory subsystem set the ceiling. Defensible ranges from benchmarking:

• DDR4 2666 CL19 versus DDR4 3600 CL16 (Ryzen 5 5600 or 5700X3D): 8 to 18 percent higher averages in CPU bound titles like CS2, Valorant, Fortnite, Warzone and Cyberpunk crowd scenes.
• DDR4 3200 CL16 versus DDR4 3600 CL16: 3 to 6 percent uplift, larger in 1 percent lows.
• DDR4 3600 CL18 versus DDR4 3600 CL16: 1 to 3 percent, biggest in simulation and MMO titles.

The 1 percent lows are the honest number. A game averaging 180 FPS but dropping to 90 in a fight feels worse than one averaging 165 and holding 130. Tighter timings improve dips more than averages.

What changes at 1440p and 4K

At 1440p and above, the GPU takes over in most titles, and memory timings collapse toward irrelevance for averages. A CL16 kit and a CL22 kit produce nearly identical numbers in a GPU limited scene. Exceptions matter: simulation (MSFS 2024, Cities Skylines 2, ARMA), MMOs (WoW, FFXIV), and competitive shooters run uncapped still show 2 to 5 percent on averages and more on lows.

If you own a 4070 Super or 7800 XT class card at 1440p, an extra fifty pounds on a CL16 kit over CL18 is a small quality upgrade. An extra hundred is not defensible on frames alone.

When to pay more, and when not to

Pay more for tighter timings if you are on AM4 or LGA 1200 building for 1080p high refresh esports, run heavy simulation or MMO titles, pair a strong CPU (5700X3D, 5800X3D, 7800X3D, 9800X3D) with a mid range GPU, or run code compiles and virtual machines.

Do not pay more if you are GPU bound at 1440p or 4K, if your CPU is a Ryzen 3600 or i5 10400 (the controller cannot exploit the tighter kit), or if the price gap between CL16 and CL18 at the same frequency is more than about twenty five percent. That money is better spent on the GPU or SSD.

For most AM4 upgrades in 2026, the right kit is 32 GB (2 x 16 GB) DDR4 3600 CL16 dual rank. Birmingham AV builds ship with that configuration where the platform supports it.

See the Birmingham AV DDR4 3600 CL16 build on eBay

Reading the label without getting fooled

A kit sold as "3600 CL18" may actually be 3600 18-22-22-42 at 1.35V, with looser secondaries than an equivalent 3600 CL16 16-19-19-39. When comparing, look at the full primary string (CL, tRCD, tRP, tRAS) and the voltage. Two "3600 CL16" kits can differ by three or four percent on tRCD and tRP alone.

Also check rank. Dual rank kits (typical of 2 x 16 GB) outperform single rank at the same timings by a couple of percent because the controller interleaves across ranks. Free uplift in 32 GB builds.

Frequently asked questions

Is CL16 always better than CL18 at the same frequency?

Yes, when the rest of the primary and secondary timings are comparable. The CL number sets a floor for how quickly the first bit of data comes back. Just compare at the same voltage and rank, otherwise the label can flatter a slower kit.

Does CAS latency matter for DDR5 the same way it did for DDR4?

The concept is identical, but DDR5 runs at much higher frequencies, so a CL30 kit at 6000 sits at the same 10 ns as a DDR4 3200 CL16 kit. The absolute CL number looks scary next to DDR4 figures, but true latency in nanoseconds is what matters.

Will faster RAM fix stuttering in games?

Sometimes. Stutters often come from cache misses that force the CPU to wait on main memory, so a lower latency kit with 1:1 fabric on Ryzen improves 1 percent and 0.1 percent lows. It will not fix stuttering caused by shader compilation, driver overhead, or a saturated GPU.

Can I mix a CL16 kit with a CL18 kit?

The board trains to the looser of the two, but mixing kits is a common cause of instability and boot loops on Ryzen. If you can avoid it, do. Sell the old kit and buy a matched pair.

About Birmingham AV

Birmingham AV Ltd has sold more than 87,000 items on eBay UK since 2017, with 24,756 buyer feedbacks at 98.9 percent positive. We are one of the highest volume refurbished PC operations on eBay UK, based in Bromsgrove, Worcestershire. Every system leaves us tested, cleaned and covered by a twelve month warranty. Companies House 12383651, VAT GB 348755066. Our DDR4 3600 CL16 systems are listed on the eBay store and shipped next working day.