More is usually better, but is there a limit to high you should go with your memory setup?
Memory upgrades are a great way to improve a computer. RAM is affordably cheap, easy to install and virtually guarantees a performance increase at any level, so resource-hungry is the software we use.
But how much RAM is enough? The average desktop contains around 2GB, but it’s not unusual to upgrade your system so that it contains 4GB, 8GB or even more than that. Since there are only four memory banks on a montherboard, there's a physical limit to how much you can install. But should you be aiming to hit that limit, or is the practical limit much lower than that?
How Much Ram Can I Have?
The amount of RAM a computer system can contain is limited, on paper at least, by the number of individual memory addresses it can access. On paper, 32-bit CPUs could access 2Л32 bytes, which is 4,294,967,296. That might look ridiculously high, but 4.3 billion bytes is four gigabytes. For reasons that are probably obvious (cost, practicality, materials scarcity), few home systems got close to that amount during most of the lifespan of 32-bit computing.
But that situation didn't last forever. Home systems starting to bump against the 4GB RAM limit is one of the things that drove the development and uptake of the 64-bit CPUs we use today - and they have a much larger upper limit on the amount of RAM they can use. Again, purely in theoretical terms, the capability of memory addressing has been raised from the fairly easy to imagine 4GB to an unimaginably high number. 2^64 is 18,446,744,073,709,551,616 (or 18.5 quintillion), which in terms of bytes is 16.8 million terabytes.
Clearly, modern motherboard architecture has no chance of ever seating that much RAM, and in any case, modern CPUs can't address that much RAM as constructed. Even if someone did try to build a system that could do it, with modern hardware, it's probable that the physical limitations of electricity would get in the way.
So if the underlying maths of computing says that the limits are that high, what is it that keeps them down?
In practical terms, it's the same thing that limits most computing performance: sheer cost. By building chips and motherboards that support a lower amount of RAM, manufacturers can save money. After all, there's no reason to make your hardware cater for systems that'll never be built.
But enough about the macro scale of RAM support. In terms of individual systems, the amount of RAM your computer can contain (and use) is limited mostly by the motherboard platform you're using.
The average consumer motherboard contains four memory banks. At present, consumer RAM is only available in 8GB modules, meaning you can get up to 32GB in a standard motherboard. At the extreme high end of the market (usually aimed at servers) DDR3 DIMMs can be bought with up to 64GB of memory on them and, combined with multi-CPU systems, it allows for up to 512GB in a single machine. It's still only a tiny fraction of what's theoretically supported by 64-bit computing, but even that's far too much for most motherboards to acknowledge.
In fact, the average home motherboard actually sets its upper limit at 32GB of RAM. Install any more than that, and the memory controller wouldn't take any notice of it anyway. High-end motherboards (such as Ivy Bridge-E motherboards and those running server platforms) do support up to 64GB, but even then they're designed for specialist use. In many cases, the software is actually ahead of the hardware. Windows 8 has no trouble supporting up to 128GB of RAM, and Windows 8 Pro (the 'enthusiast' edition) supports up to 512GB.
So now we know. Unless you've built a server or specialist system, the most RAM you can have is 32GB. But that's only part the issue. Before we can figure out how much RAM you need, we have to understand why it's useful to install more at all.
How Does RAM Speed Up Your System?
RAM might be as cheap as it's ever been right now. 32GB doesn't quite cost pocket change, but it's no more expensive than a high-end graphics card or SSD - significantly less so, in fact. Assuming you can afford to spend that much, we now need to ascertain whether it's actually good value to do so.
For the most part, installing more RAM in a system is a good idea. Extra memory doesn't speed up the processor itself, but it can ensure that the processor is never waiting for the data it needs. More RAM means less need to shift data in and out of virtual memory (which is stored on the slow, bottleneck-inducing hard drive) and therefore a smoother, speedier execution of any large operation.
This means the benefits of adding RAM are normally clearest in things like application opening times, boot times and file processing times. It's purely because your system has a reduced reliance on virtual memory, allowing you to fit more data in real RAM, whether that's browser tabs, uncompressed photo data or large files. If you don't have enough RAM, the system uses the virtual memory swap file as a temporary store, which slows down execution.
Modern PCs already rely far less on virtual memory than those of the past thanks to the comparatively large amount of RAM systems contain, but that's not the only factor. More and more systems use SSDs instead of mechanical drives, and solid-state hard drives are made from stuff that’s a lot like RAM already. The bottleneck that occurs from using virtual memory is dramatically reduced if your main storage unit is an SSD. That's why you should always use the SSD to house your Windows installation.
But SSDs are only fast to a point. They might be ten times faster than hard drives, but RAM - real RAM - is significantly faster even than that. The average SSD can read and write data at 500-600MB a second. A DDR3 module running at 1333MHz can transfer over 10GB a second. So even if you're running a high-end SSD, your system would still benefit from having enough RAM that it could all but ignore virtual memory.
Windows versions since Vista also speed up your system using a technology called 'SuperFetch'. This works silently in the background to try to guess which program you'll use next and loads it into RAM before you actually run it, so that when you do, it can appear almost instantly rather than take its time loading from disk. It's a small convenience but one that shaves the most frustrating seconds off program launch times, and when you have more RAM installed than you use, Windows is able to load more programs that it thinks you might soon need, reducing the chance that the program you want won't be in RAM when you want it.
In terms of actual numbers, adding 2GB of RAM to a 2GB system has the most dramatic effect, giving you a 10% reduction in app loading times. A further 4GB (so the system totals 8GB) will increase space for SuperFetch to work, reducing app loading times by a further 5% or there abouts. SuperFetch is one of the few uses of RAM that doesn't have an upper ceiling, but it does depend on your system being idle enough for it to devote resources to SuperFetch.
We should note that those numbers apply to application multitasking use. Games don't necessarily use RAM the same way. For a start, most games don't require huge amounts of RAM, because a large proportion of their memory requirement is used for visual elements - particularly textures -which are loaded into the video memory. Games also tend to be the only major task while you're running them, so the overall system requirements aren't high either.
Again, to give hard numbers, if you upgrade from 2GB of RAM to 4GB, you'll probably see around a 10% decrease in game load times and a 15% increase in frame-rates at full HD. If you upgrade from 4GB of RAM to 8GB, you're likely to see much smaller performance improvements - maybe another 5% improvement in full HD framerates. If you already have 8GB and you upgrade further, you'll see virtually no improvement - especially if you're using a mechanical hard drive, which bottlenecks the RAM throughput.
How Much RAM Do I Need?
At this point, we reach the big question: how much RAM do you need? It's a simple question but one that has a complex answer. After all, it depends on what you want to do with your system and how you use it. But that's also a bit of a cop-out answer, so here's our attempt to produce some actually useful guidance.
The first point of call is your operating system. Windows 7 and Windows 8 both claim that they need 1GB of RAM for 32-bit mode and 2GB of RAM for 64-bit mode. These are the bare minimum requirements. If you want a PC that'll run, rather than one that'll run well, this is the bar you have to clear.
Instantly, we can provide some guidance. Whatever the minimum requirements are for your operating system, double them. 2GB for 32-bit Windows, 4GB for 64-bit Windows. That'll get you well on the way to avoiding the disk-churning fate that awaits minimum-requirements users. If you can afford to double that, you'll see some further improvements but not a huge amount. Once you've doubled the minimum amount of RAM, any more you add is purely for performance fine-tuning and certainly not because it's good value for money.
But if that's a rule of thumb, how can you tell what the specific requirements of your system are? What if you're an outlier in the way you use your system, but don't realise it? Well, here's a way you can check RAM usage with the Windows Performance monitor.
To access the Performance monitor, open Task Manager (press Ctrl-Alt-Del and select Task Manager), and then click on the ’performance' tab. You'll get a rough overview of your CPU and memory usage. You'll see CPU usage graphs for each core of your processor, and one of your physical memory usage. Here's how to interpret the latter graph.
On the left, in the 'memory' box, you'll see a physical representation of how much RAM you're using out of your currently available amount. The green number at the bottom indicates the exact amount - in our case, 2.19GB. On the right is a constantly updated line chart of RAM usage, which changes over time as you open and close applications.
A simple test is that if the blue line ever reaches the top of the chart, Windows has been forced to use virtual memory where it would rather be using physical RAM. If that happens, an extra couple of gigabytes should result in a significant performance improvement. Alternatively, if you can't ever get the RAM usage to spike high enough to be a problem, Windows is going to see only very small improvements from being given additional RAM, so the money might be better spent elsewhere.
Although upgrading your RAM past 4GB does mean you're dealing with diminishing returns (and even more so once you go past 8GB), it's worth remembering that there are always small improvements from adding RAM (which makes it a good way to add speed to an otherwise plateaued system) and that what's true now might not be true tomorrow. 4K video and media-heavy web pages are becoming more common, and both of these things will make your system need extra RAM the more they get used. If you're building or upgrading a system today, stuffing it full of RAM might not yield much extra performance today, but it's definitely a good way to future-proof it.
What's The Alternative?
If you're wondering whether there might be another option, there is. Rather than upgrading your RAM capacity, you could upgrade your RAM speed. RAM modules are rated for a certain clock speed (typically 1333MHz or 1666MHz), but if you're running a new enough system with a fast processor, you might want to look at buying faster RAM instead.
After all, gaming system benchmarks have shown that running RAM at 2133MHz rather than 1333MHz can result in around a 30% increase in frame-rates, because the RAM operations are happening at a much higher speed.
The only problem with this is the price. A 4GB DIMM rated at 2133MHz is almost twice the price of its 1333MHz counterpart, since the faster module requires better materials, more QA and extra components like a heat spreader or cooling fan attachment. You also have to junk your old RAM, since you can't have modules running at different speeds.
But it does seem as though RAM quality, rather than quantity, is what's going to matter in the future. It'll be years before the average home system routinely needs more than 8GB of RAM. If you want to get the edge over your friends and improve the way your system performs, the question isn't 'How much RAM do I need?', it’s 'How fast should my RAM be?’ And the answer to that question is simple: as fast as possible.