This article was published in the September 2015 issue of Maximum PC. For more trusted reviews and feature stories, subscribe here.
It's tempting to always get the biggest and fastest memory kit, but how much RAM do you actually need?
Component lifespans are usually pretty easy to track. Processors get higher clock speeds, more cores, and smaller silicon; graphics cards get better clocks, more transistors, and bigger heatsinks; and storage gets bigger and cheaper.
Memory is another component that's constantly evolving: faster speeds, bigger quantities, more channels. Conventional wisdom suggests that adding faster and larger amounts of memory will allow games and applications to run faster, but that's not always the case, which is why we've examined this murky situation.
The Memory Landscape
Computer memory is currently divided into two main types: DDR3 and DDR4. The former is older, having debuted back in 2007, while the latter only hit the mainstream recently, with Intel's X99 platform in 2014, and more recently with Skylake's Z170 platform.
They both work using the same principle: DRAM chips store data that the computer needs immediately, but it's lost when it's no longer useful or the PC is turned off. It's governed by several common attributes: Larger amounts mean more data can be stored, and higher MHz ratings mean the memory runs at a faster speed, so data moves in and out more rapidly.
The newer standard, DDR4, has several advantages over DDR3. It runs at a higher frequency, so it's able to process tasks at a faster rate: DDR3 is generally clocked between 1,333MHz and 2,400MHz, while DDR4 ranges from 2,400MHz to 3,200MHz and beyond. It's possible to blur these lines with overclocking, but, for the most part, DDR4 is faster. It balances those better speeds with more efficient power consumption, and its chips have double the internal memory banks, faster burst access, and higher data transfer rates.
DDR3 and DDR4 memory work with different motherboards and chipsets. DDR3 memory is compatible with nearly every motherboard and socket type you're able to buy right now, while DDR4 memory is only compatible with boards that use Intel's X99 chipset and LGA2011 processor socket, or the new Z170 boards with DDR4 sockets. (Note that some Z170 boards will support DDR3 instead of DDR4.)
DDR4, however, does have one downside. That's increased latency. Newer DDR4 2,133MHz memory has a latency rating of CL15, which means it'll take 14.06ns to perform a read, while DDR3 1,600MHz memory reads at 13.75ns. That's a tiny margin, and DDR4 negates this disadvantage with its generally higher clock speeds. Nevertheless, if you'd like to keep an eye out, look for CAS ratings. This indicates latency, and lower is better.
No matter which memory you buy, you'll have to deal with channels. Dual- and quad-channel setups are the most popular and improve performance by allowing motherboards to use multiple channels to send and receive data simultaneously, thereby improving bandwidth. It's possible to run memory in single-channel mode, but there'll be a performance decrease if you run a single stick of memory rather than two or four.
Different locations of the key notch (on the insertion edge of each DIMM) prevents a DDR3 or DDR4 stick from being installed into an incompatible board or platform.
The Changing PC Landscape
The variety of different specifications means that prices vary wildly. The cheapest 16GB DDR3 kits made from two 8GB sticks currently cost about $90, but the most expensive can cost more than $300. It's a similar story with DDR4, where dual- and quad-channel kits also vary by huge amounts when it comes to price. But these will generally be more expensive than their DDR3 equivalents.
Manufacturers claim that the increased speeds and better features provided by pricier memory will make a dramatic difference to performance, but we're not so sure, so we've set up some test rigs to find out just how much memory you really need. Both of the test rigs we've set up use MSI motherboards. One uses Intel's Z97 chipset with a Core i7-4770K processor, while the other is an X99 rig with a Core i7-5820K chip. Both use operating systems installed on a Samsung 850 Evo SSD, and both use an Nvidia GeForce GTX 980 graphics card.
We've already mentioned the different processors and chipsets that work with DDR3 and DDR4, but there's more to choosing components than just making sure your new gear is compatible on paper. Intel's Haswell architecture is behind the bulk of its current desktop processors, and it supports up to 32GB of dual-channel memory. It's used for chips that range from cheap Celerons and Pentiums to more expensive Core i5s and i7s, and these desktop Haswell chips all plug in to the LGA1150 socket. Most Haswell-based processors are deployed with mobos that have Intel's H87, Z97, and Z87 chipsets. When it comes to memory support, they're all impressive. They handle four slots that accommodate two sets of dual-channel memory, and most full-size ATX boards also support 32GB or 64GB of memory at high speeds.
Intel has further developed its architecture with Haswell-E. Chips that use this system also use the LGA2011 socket and X99 chipset, which means that support for DDR4 is included. That in turn means support for faster memory speeds when compared to DDR3, and the X99 platform is quad-channel.
AMD's processors and APUs, meanwhile, use the Piledriver architecture. Its own memory controller was given a speed boost over the previous generation of AMD hardware, but memory support ultimately still isn't as good on this side of the fence. All of AMD's current chips support DDR3 memory, however, some of them are restricted to 1,600MHz or 1,866MHz memory, while only a handful officially top out at 2,133MHz (though some enthusiast mobos allow you to overclock the RAM to higher speeds). Like Intel mainstream platforms (LGA1150/1151), these boards support dual-channel memory.
Don't Forget Your Mother
Processors and chipsets aren't the only bits of your PC that need to be checked before shelling out for new memory—motherboards are also vital. You'll need to make sure a board has the right number of slots, and also check what amount and speed of memory it can accept: It's no good dropping a few hundred bucks on a 32GB 3,000MHz kit if your motherboard taps out at 16GB and 2,666MHz.
There are nuances to be examined, then, but for the most part, the memory landscape is heartening. No matter what processor, chipset, or motherboard you use, you'll be able to equip a rig with plenty of high-end memory at decent speeds. That's good for PC building, but it's not necessarily great news for companies that rely on flogging expensive, high-end kits.
Future developments from Intel and AMD will only improve the situation. Intel's newly launched architecture, Skylake, supports DDR4 across all of its full-fat desktop chips, but it'll also be backward-compatible with DDR3, which adds a huge amount of versatility. (Again, pay attention to the number and type of memory slots, as you cannot use DDR3 sticks in a DDR4 slot of vice versa.) We also expect to see improvements to the memory controller and support for larger amounts of memory running at faster speeds.
AMD isn't standing still, either. Its next proper desktop architecture is called Zen, and it'll offer full DDR4 support to bring the company's chips alongside Intel.
The X99 chipset introduced DDR4 to the high-end consumer market, bringing with it faster clock speeds and better power efficiency, but with increased latency.
DDR3 Memory
The first set of DDR3 benchmarks we locked and loaded were PCMark 8's Home, Creative, and Work tests—a trio of suites that simulate the kind of low-intensity tasks that take place on many systems, from web browsing and video chatting to word processing and spreadsheets.
Our first tests deployed the bare minimum of sluggish DDR3: 8GB of RAM clocked at 1,333MHz. With this RAM, the rig returned scores of 5,170, 6,794, and 5,234 points, in the Home, Creative, and Work tests, respectively. However, with 8GB of 1,600MHz memory deployed, the scores barely improved, with the Creative run only jumping to 6,852.
There wasn't even much of a difference in these tests when we installed 16GB of 1,866MHz memory: In those three benchmarks, the machine scored 5,270, 6,961, and 5,225. The biggest leap came in the Creative test, which suggests more memory helps with photo editing and other trickier tasks, but it's hardly a game-changing jump in performance.
We saw similarly modest gains in other photo-related applications. GigaPan Stitch knits together a group of high-resolution photos, and our test image took four minutes and 12 seconds to complete in a rig with 8GB of 1,333MHz memory. That only improved by 11 seconds when we doubled the RAM and upped its speed to 1,866MHz.
Other application benchmarks saw similarly modest impacts. A Cinebench R15 CPU test with two 4GB, 1,600MHz sticks returned a result of 703; doubling the memory and improving its speed to 1,866MHz only improved that figure to 751.
We only saw big improvements in a few benchmarks when running DDR3 tests. In PCMark Vantage, our 8GB 1,600MHz rig scored 18,313 points, but doubling the memory and running it at 1,866MHz saw that result jump by almost 3,000 points—a significant increase.
Indeed, our theoretical tests indicate that improving memory amounts and speeds does make a difference, but that these gains don't generally translate to real-world tests.
In SiSoft Sandra's multithreaded bandwidth test, our 2x 4GB 1,333MHz setup scored 16.57GB/s, but doubling the memory and improving its speed to 1,866MHz saw that result jump to 23.33GB/s. There was a decent jump in single-threaded bandwidth, and cache bandwidth also improved significantly when faster memory was added in larger amounts.
The leap from two to four memory sticks doesn't often have much of an impact on our application tests, either. In Cinebench R15's OpenGL test, a machine with two 4GB 1,600MHz sticks scored 111 frames per second, with this score only jumping to 117fps with four 4GB 1,600MHz sticks installed.
When running applications using DDR3, then, the differences between slow and fast memory often aren't huge—and, as long as you've got 8GB of memory installed, then you're going to have enough to get most stuff done in real-world situations.
There was a noticeable performance difference between our rig with 1,333MHz and 1,600MHz memory installed, but, once beyond that 1,600MHz speed, the gaps between different memory speeds narrowed rapidly. We ran GeekBench single-core benchmark on 1,600MHz memory, and then again at 2,800MHz memory, but its result only improved by around 100 points.
The benchmarks demonstrate that there are performance gains to be had by installing more memory at faster speeds, but those gains are only noticeable in high-end applications. For most of us, 8GB or 16GB of 1,866MHz memory will be more than enough.
DDR3 and Gaming
We tested a variety of games using our DDR3 rig, but only found sporadic improvements. In Metro: Last Light, a machine with two 4GB 1,333MHz sticks averaged 126fps, but improving to a pair of 8GB 1,866MHz DIMMs saw that result jump to 144fps. In both Bioshock Infinite and Batman: Arkham Origins, though, the improvements were far less impressive—a few frames better in the minimum frame rate benchmark, and only a gain of 2fps to the average rate.
There also wasn't much of a difference in any of our Unigine Heaven 4.0 tests. In all of our DDR3 tests—ranging from a system with two 4GB 1,333MHz sticks to a machine with four 8GB 1,600MHz DIMMs—the benchmark's average frame rate hovered between 63.4fps and 66.8fps. Those configurations didn't differ much in 3DMark's Fire Strike test either: in the same range of memory setups, our results only jumped between 11,607 points and 11,635 points, well within the margin of error.
Whether you've got DDR3 or DDR4, upping the size or speed of your memory makes little difference to Bioshock Infinite. Crucial's Ballistix sticks, left, look good, but also come with handy extras, such as integrated thermal sensors.
The DDR4 Difference
Newer DDR4 memory operates with faster speeds, better channel support, and Intel's latest enthusiast chipset and controller, so we expected our tests to reveal bigger performance disparities. Our initial tests, though, appeared to follow the blueprint already set out by the older DDR3 sticks.
In the Cinebench R15 CPU test, a machine with two 4GB 2,400MHz sticks scored 1,143 points. Doubling the memory and increasing its speed to 3,000MHz, however, only saw that result jump to 1,190. The X264 video encoding test led to similar patterns. Our more modest rig ran through its two tests at 205 frames per second and 68 frames per second, but increasing the memory's speed to 3,300MHz saw those results only inch forward to 211fps and 73fps—hardly a jump that'll make a big real-world difference.
GigaPan Stitch's photo-editing tool only saw a couple of seconds' worth of improvement with its memory sped up, while Geekbench exhibited similarly small gains: Our first DDR4 rig scored 22,165 points, but doubling the memory to 8GB, running at 2,666MHz, only saw the score jump to 22,849.
It's a shame because, as with DDR3, theoretical tests illustrated that improving speeds and amounts did make a difference. When we had two 4GB 2,400MHz sticks installed, our test rig delivered 15GB/s and 28.58GB/s of single- and multi-threaded bandwidth, with those numbers jumping to 17GB/s and 32GB/s with those same sticks clocked to 3,300MHz.
Those same benchmarks illustrated how DDR4 copes with quad-channel and larger amounts of memory: Our machine with two 8GB sticks may have delivered 32GB/s of multi-threaded bandwidth, but doubling the memory (and channels) saw that figure leap to 45GB/s. Quad-channel delivered impressive numbers throughout our benchmarks, then, but those figures weren't always translated to real-world tests. So, we'd say that it's not a vital addition to your PC, unless you're keen on buying a Haswell-E system to run intensive work applications or the most demanding games.
DDR4 and Gaming
We saw a big jump in just one of our gaming benchmarks, Metro: Last Light, while testing with DDR3. However, updated DDR4 memory proved even less dramatic. Improving the amount and speed of memory saw our Metro: Last Light results jump by a mere couple of frames, and our biggest improvements in Bioshock Infinite and Batman also only saw increases of a frame or two, no matter the amount or speed of DDR4.
We'll let Unigine Heaven have the last word. Our rig averaged 62.7fps with two 4GB 2,400MHz sticks installed, but this only improved to 64.2fps once we installed four 8GB 2,666MHz DIMMs.
There's no doubt about the pure, naked speed of DDR4, but it looks like we're at the point, for gaming especially, where any 8GB dual- or quad-channel configuration will be ample. Memory simply isn't the bottleneck in gaming. Processors and graphics cards are the components that are more likely to be holding back your frame rates.
| Benchmarks |
| | DDR3 | DDR4 |
| 8GB (2x 4GB) 1,600MHz AMD AE34G1609U2
| 8GB (2x 4GB) 1,333MHz Corsair CMV8GX3 M2A1333C9
| 16GB (2x 8GB) 1,600MHz CML16GX3 M2A1600C9
| 16GB (2x 8GB) 1,866MHz Crucial Ballistix Sport XT | 8GB (2x 4GB) 2,400MHz Kingston HX424 C15FBK4/32
| 16GB (2x 8GB) 2,666MHz Ballistix BLE2C8 G4D26AFEA |
Cinebench R15 (index)
| 703
| 738
| 751
| 721
| 740
| 747
|
PC Mark 8 (index)
| 5,161
| 5,170
| 5,228 | 5,270
| 5,320
| 5,364 |
PC Mark Vantage (index)
| 18,313
| 19,718
| 20,944
| 20,427
| 26,541
| 28,088 |
3DMark Firestrike (index)
| 11,624
| 11,607
| 11,608
| 11,635
| 11,820
| 11,920 |
X264 v4.0 (fps)
| 66.6
| 66.1
| 69.3
| 69.4
| 68.6
| 72.6 |
SiSoftware Sandra Memory bandwidth (GB/s)
| 21.1
| 16.6
| 20.6
| 23.3
| 28.6
| 31.8 |
Gigapan Stitch (secs)
| 248
| 254
| 242
| 241 | 245
| 244 |
Bioshock Infinite (min/avg fps)
| 11 / 109
| 11 / 115.9
| 11.6 / 115.3
| 13.2 / 117.6
| 33.2 / 122.6
| 44.5 / 124.7 |
Batman: Arkham Origins (min/avg fps)
| 100 / 135
| 99 / 137
| 103 / 137
| 106 / 139
| 104 / 136
| 104 / 133 |
Unigine heaven min/avg (fps)
| 26.5 / 64.1
| 25.2 / 63.4
| 26.8 / 63.6
| 26.2 / 63.6
| 28.6 / 62.7
| 27.8 / 62.7 |
Best scores are bolded.
What Memory Do You Really Need?
It's tempting to buy the fastest and largest memory kit you can afford when putting together a new build, but, as many of our benchmarks illustrate, aiming for the top of the tech tree is actually an unnecessary extravagance when it comes to memory.
The story is the same whether you're creating a PC using DDR3 or DDR4. A decent amount like 8GB or 16GB running at a reasonable speed will be enough to handle most tasks you throw its way, whether it's for work or gaming. You'll still see occasional benefits if you buy larger and faster kits, sure, but they'll be less significant—so, it's only worth looking toward these kits if you're a true enthusiast who wants the best parts available, or if you're running unusually demanding software and need to wring every last bit of performance from your PC.
Quad-channel kits, meanwhile, are great if you're using applications that'll truly take advantage of DDR4's improved architecture, such as encoding or rendering, but most people won't feel the benefit. It's no surprise, then, that it's only available with expensive X99-based CPUs (as well as the earlier X79-based platforms, which used quad-channel DDR3).
The majority of PC users, even enthusiasts, just don't need to cough up for the priciest kits around, and that's definitely no bad thing. Memory, processor, and chipset developments have leveled the playing field, which means it's one less component to worry about when putting together a new PC.
The Aesthetics of Memory
Memory manufacturers try to sell expensive kits on the basis of their size or speed, but that's not the only advantage that comes from spending big on a high-end set of DIMMs—many of them are also designed to look better than their cheaper, plain-looking alternatives.
Corsair's Dominator Platinum range sits at the top of the firm's product stack, and some of its key benefits are about the visuals. Corsair boasts of its industrial design and LED lighting—the top metal bar can be upgraded with different attachments, the LEDs can be changed, and the box has a good-looking fan kit that can sit on top of the sticks to provide extra cooling.
Expensive memory kits like this don't just have aesthetic advantages—Corsair's Dominator Platinum chips are hand-sorted, have improved monitoring hardware, and better heatsinks. But there's no denying the visuals play a key part when it comes to high-end memory.
Other firms offer similarly high-end extras. Crucial's Ballistix memory sticks have attractive aluminum heatsinks alongside practical extras like integrated thermal sensors, while Kingston's HyperX Predator and Beast products have good-looking exteriors, but are chosen specifically to provide the best performance.
Kits like this bring practical and visual improvements to the table, then, but they're not always necessary. If you're building a midrange rig, or want to put together a machine without a window in its case panel, they're simply overkill.
Pentiums, Celerons, and APUs: Buying Memory for a Budget PC
Our tests have examined the effect of different memory on high-end machines, but if you're building a budget rig, then different considerations should come to the fore at checkout time.
For starters, don't splash out on an expensive, fast memory kit if you're going to be constructing a PC built around one of Intel's Haswell-based Celeron or Pentium chips, as most of these only support DDR3 that runs at 1,333MHz. That's slow enough to cause a performance hit in many tests, but on a low-end rig, it's unlikely you'll be running the sort of applications that'll suffer with lesser speeds.
Don't bother with high-end memory if you're running an A10-7850K or Pentium K.
AMD's APUs are more accepting to faster memory, but you'll still need to pay attention to speeds. A couple of its cheapest parts only handle 1,333MHz or 1,600MHz DDR3, but most can support 1,866MHz sticks. It's the same on the CPU side, with FX chips mostly supporting 1,866MHz parts.
There's one other main consideration when putting together a budget machine: the motherboard. Budget boards don't often support the extreme speeds offered by pricier components, and many—especially at smaller form factors—only have two slots, rather than four. That's fine if you're building a system you don't intend to upgrade, but it can prove restrictive if you want to add more memory later.
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