How much RAM do you need, should you upgrade it, and will it speed up your PC? – ExtremeTech
Welcome to ExtremeTech’s comprehensive RAM guide, in which we’ll answer a broad range of questions related to how much system RAM you need these days, whether or not it’s worth it to upgrade older systems, and whether DDR3 or DDR4 (the new main types of system RAM) is a better investment option.
It’s interesting to look back and see how much things have changed over the past twenty years. People have been writing RAM guides for decades, but back when I was learning about computing, much more emphasis was paid to the specific technical implementation of any given RAM standard. Fast Page Mode RAM, EDO RAM, SDRAM, DDR, and RDRAM are just a few of the standards that existed elbow-to-elbow, and which type of memory your system used often determined if it was worth upgrading.
Nowadays, things are simpler. While a few of you may still have DDR2-based equipment from 2005 to 2009, the majority of systems today are likely using DDR3. That’s the memory standard we’ll focus on; if you have DDR2-related questions you’re welcome to drop them in the comments.
How much RAM do you need?
How much RAM you need in a system depends on what you intend to do with it, how long you intend to keep it, and whether or not you can upgrade your memory post-purchase. This last point is important, as many high-end laptops have eliminated user-upgradeable RAM in order to reduce system thickness by roughly six nanometers.
Adding additional RAM to any laptop generally increases power consumption by a measurable (if small) amount, but this shouldn’t be an issue for most users. It’s also better to have a bit too much RAM than too little, as whatever you gain in power savings you’ll promptly lose to increased disk paging.
Apple’s MacBook Air offers 4GB of RAM, but most of the systems from Dell, HP, and other OEMs start at 8GB, and I think that’s the better sweet spot. That’s not to say you can’t get by on 4GB — you absolutely can — but 8GB gives you a bit more breathing room.
There’s at least some evidence that modern desktop applications have slowed the rate at which they demand more RAM. From 1990 to 2000, Photoshop’s minimum RAM requirement rose from 2MB to 64MB, a 32x increase in 10 years. It took another 16 years to match this early rate (from 64MB in 2000 to 2GB in 2016).
A lightweight system today can get by with 4GB of RAM. 8GB should be plenty for current and near-term future applications, 16GB gives you comfortable space for the future, and anything over 16GB is likely overkill unless you specifically know you need it (such as for video editing or audio post-production). This holds true for desktops as well as laptops.
DDR3 or DDR4?
Right now there’s plenty of DDR3 systems still being sold, but DDR4 has already begun to replace it on the mass market. If you’re building a new system and don’t have a specific reason to use DDR3, we’d recommend buying hardware that’s compatible with DDR4.
With that said, if your system does use DDR3, that’s not the problem that it used to be. In the old days, a computer stuck on, say, PC133 SDRAM was at an intrinsic performance disadvantage compared with systems that used DDR, particularly at higher clock speeds. That’s less true than it used to be, and it may make sense to upgrade a DDR3 system depending on what you have and when you bought it. The reason to use DDR4 at this point has more to do with long-term memory pricing trends and future compatibility than fundamental performance. We’ll explore current price and the performance question later in this guide.
Does faster RAM boost system performance?
Short answer: Sometimes, but not by much.
Medium answer: It depends on other system components, workload, and whether or not you’re using integrated graphics.
Longer answer: See below.
RAM performance is controlled by two metrics: Clock speed and access latency. Access latencies tend to fall much more slowly than clock rates — as this diagram shows, the memory cell cycle time of PC100 is roughly equivalent to DDR4-2133. DDR4 doesn’t match DDR3-2133 cycle times until you hit DDR4-4266.
Conventional wisdom is that RAM latency has become relatively less important in recent years, thanks to a combination of factors. Back when L2 caches were small, memory controllers were off-die (and clocked at a fraction of CPU speed), and there were no L3 caches, memory latency had a larger impact on overall system performance. Modern CPUs are typically backed by 512 to 1MB of L2 (per core), and 1.5MB to 2MB of L3 cache (per core). Memory controllers are now integrated on-die and run at full processor speed. As a result, RAM latency simply doesn’t play as large a part as it once did in determining performance.
As for raw memory bandwidth, the same large caches that minimize the impact of RAM latency in most applications also limit the impact of memory bandwidth. Desktop applications are, for the most part, latency-sensitive, not bandwidth-sensitive.
There’s one major exception to this rule: Integrated graphics performance. Both Intel and AMD integrated graphics see some benefit from higher-speed memory, but the gains are particularly large on the AMD side. This has proven true for every APU since at least Trinity, and will likely continue to be accurate for DDR4-based hardware. The advent of HBM2 in APUs will finally throw open the bandwidth floodgates — until then, integrated graphics will always be somewhat bandwidth-limited.
What about high-end gaming performance?
Until recently, I would’ve told you that high-speed RAM had very little impact on high-end gaming. A recent report from Digital Foundry, however, appeared to show otherwise.
Digital Foundry’s full review is worth a read — they tested a Core i5-6500K with a GTX Titan X at 1080p in a variety of titles to measure both the impact of overclocking DDR4 and of higher clock speeds. What we’ve done below is map the gains they saw from overclocking DDR4 from 2133MHz to either 3066MHz or 3200MHz. These two clock speeds always delivered the best performance, but some titles showed the greatest gains at 3066MHz and regressed at 3.2GHz, while others showed continual improvement.
This dataset is limited, but it does point to some general trends. First, minimum frame rates tend to increase more than average frame rate. Second, the gains are title-specific: Battlefield 4, Crysis 3, and COD Advanced Warfare all see gains under 10%, while GTA V, Far Cry 4, and The Witcher 3 are all at or above the 15% mark. Assassin’s Creed Unity splits the difference, with a 15% jump in minimum frame rates and a 6% rise in average frame rates.
The Digital Foundry team claims to see a similar set of results when using faster DDR3 in Fallout 4 and a GTX 970. As this screenshot shows, FO4’s minimum frame rate rises dramatically when paired with DDR3-2400 instead of DDR3-1600.
Again, however, a caveat is in order. Gamebryo games have always tended to be very friendly to more memory bandwidth — much more so than you would otherwise expect. We’ve seen this in Skyrim, and we’re seeing it, apparently, in Fallout 4 as well. TechSpot has more on this, and their data shows that Intel chips gain more than AMD does from faster DDR3. This actually makes sense — the FX-8350’s L3 and integrated memory controller are clocked at 2.2GHz, and the FX-8350 has other latency issues that will blunt the impact of faster RAM.
The non-Fallout 4 gains aren’t huge, considering that we’re increasing RAM clock by 50%, but these results fly in the face of previous testing. For years, conventional wisdom has been that RAM clock speed is nearly irrelevant to game performance, provided that you’ve met the minimum threshold for a title.
It’s possible that we’re seeing the impact of new game engines or that the GTX Titan X that Digital Foundry used was powerful enough to show an impact, whereas previous video cards were not. The choice of resolution (1080p) and potentially even the use of FCAT over FRAPS could also have played a part.
One major point to be aware of if you intend to try and run extremely high memory clocks: If you’re buying a bunch of DDR3-1600 (or DDR4-2133) to stick in a box, you probably don’t need to worry about sticking to the “manufacturer recommended” section of your motherboard manual. If, on the other hand, you want to run maximum clock speeds, take the time to review precisely which RAM your motherboard vendor recommends you use. Keep in mind that running high RAM clocks is often at odds with running large amounts of memory. Single-sided DIMMs tend to tolerate high frequencies and low latencies better than double-sided memory, and you ideally don’t want to use more than one DIMM per channel unless your motherboard vendor specifically recommends differently.
Skip this step, and you may well end up with memory that can’t reach its full potential in your system.
Next, we’ll cover upgrading and cost. What clock speeds make sense, and which don’t?
Before we discuss the upgrade question, let’s have a look at what you can expect to pay for DDR3 and DDR4 today. We compared the price of 16GB of DDR3 and DDR4 memory throughout their respective clock frequencies, using Newegg.com as our source.
DDR3 prices are fairly stable until you reach DDR3-2666. DDR3-2400 may be worth the extra dollars, since you’re paying 18% more and receiving a 50% clock boost, but nothing above 2.4GHz is worth your cash.
The rapid price increases above 2.4GHz don’t just reflect enthusiast price gouging, but the difficulty of getting good yield on DDR3 memory at these frequencies. DDR3 wasn’t designed to scale to such high clock rates, and the 2666MHz price reflects that.
DDR4 shows a more leisurely curve. There’s no single inflection point at which cost skyrockets. $105 for 16GB of DDR4-3200 isn’t a bad deal if you can spare the cash — and if you can’t, 16GB of DDR4-2133 isn’t going to leave you gasping in the latest games.
Should you upgrade older systems?
Upgrades are another area that deserve consideration. There are plenty of first-generation Core i7 systems that likely opted for DDR3-1066. If you’ve got a Core i7 rig from this era with 4GB to 6GB of relatively low-speed DDR3, is it worth upgrading to high-speed RAM?
The answer here is probably, but I wouldn’t go overboard. 12GB of DDR3-1600, for example, is around $60 at Newegg. Higher frequency kits aren’t always offered in the multiples of 3 that the old X58 motherboards liked best, but if you can find a DDR3-1866 kit that matches your board and doesn’t cost much more, I’d say go for it.
There are, however, some caveats to this position. AMD’s Phenom II and first-generation Intel Core i7 products (Nehalem microarchitecture, codenamed Bloomfield or Lynnfield) all used “uncore” clock speeds well below the CPU clock. The Phenom II’s L3 cache and integrated memory controller were clocked at 2GHz, while the Core i7 920 and 940 were clocked at 2.13GHz. This will limit the benefit you see from faster DDR3 unless you also overclock the uncore; clocking memory faster than the memory controller rarely results in improved performance.
AMD Bulldozer and Piledriver CPUs both use uncore clocks around 2.2GHz, as do the company’s APUs. Intel switched to an uncore clocked at base CPU frequency with Sandy Bridge, which typically means 3GHz or more.
DDR3-2133 should be considered the highest-end “practical” upgrade clock for older hardware. If you’ve already got 8-16GB of DDR3-1600 I wouldn’t bother, but if you opted for DDR3-800 to DDR3-1066 when you built your system and have just 4-6GB of memory in it, you may see some modest improvements for relatively little cost. Be advised, however, that a faster GPU will usually be the better system upgrade if you have to pick between RAM and graphics, and can’t afford to do both.
Putting it all together
We’ve touched on a great many topics in this story, so I’ll summarize the findings here. If you’re planning to buy a new laptop, check to see if it allows for RAM upgrades or not. This isn’t a given anymore. Mobile users with light use cases can get by on 4GB of RAM; 8GB is a good target for the majority of people. If you’re a gamer, photo/video editor, or planning to do CAD/CAM work, we recommend at least 16GB of memory. Chances are if you need more than that, you already know it.
If you’re a desktop user with an older system, especially an older enthusiast rig, adding faster RAM may help you eke a few more years out of your hardware, especially if you only have 6GB of RAM today.
Gamers looking to build new desktops should target DDR4 and a 16GB sweet spot. Higher frequency DDR4 is better than lower, all else being equal, but don’t worry about your rig being crippled if you need to shave a few dollars off the cost. DDR4 will be on the market for years to come and the prices will inevitably come down further. This is particularly true if you’re going to build with a midrange GPU; a GPU-limited game won’t see a huge performance shift from using faster DDR4.
If you want to install massive amounts of memory now, there’s nothing wrong with jumping for 32GB of DDR4, but I don’t expect it to be of much practical benefit for the overwhelming majority of people. Most applications take their memory consumption cues from Microsoft, and Microsoft has held the bar steady on Windows for a very long time. If you’re planning to edit 5K videos or RAW 4K camera footage this obviously doesn’t apply to you — stuff as much RAM in your chassis as you like in that case.
Hopefully this helps clear up questions, but if you’ve got an issue I haven’t touched on, sound off in the comments below.
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