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Random Access Memory (RAM)
RAM can be considered a liaison between your CPU and your hard drive or SSD. It’s aptly named “Random Access” memory because of its incredible speed at accessing random blocks of data. You saw how fast an SSD’s 4K random read/write speeds are. RAM is several times faster than that, and that’s why we need RAM to store the data that the CPU needs to access for our running applications. As discussed in the motherboard section, we will be using DDR3 RAM only. No other type will be compatible with today’s motherboards.
RAM comes in a variety of capacities, speeds, latencies, voltages, and heat spreader designs. Image: http://img443.imageshack.us/img443/5312/1ue3.png width=400 Corsair Vengeance series DDR3 RAM modules with various heat spreader color options. Image: http://img703.imageshack.us/img703/9356/j0om.jpg width=400 A RAM module without a heat spreader. ====///====How Much RAM Do You Need?====\\\====
More RAM means better multi-tasking, so what you plan to use your PC for (besides gaming) is a factor in making this decision.
These days, RAM capacity is measured in gigabytes. Dual channel configurations are sold in “kits” of two or four RAM modules (or sticks) of equal size. As discussed in the Motherboard section, the extra bandwidth of dual channels makes it a no-brainer that we would want to take advantage of it, which requires at least two modules. So, bearing that in mind, here is a run-down of the various capacities of dual-channel RAM available: 2GB
—This is essentially the minimum you’d want in any modern PC with which you intend to do more than surf the web. You’ll be able to run games and power-user software, but at this capacity, your RAM is going to be a huge bottleneck. Most games today can easily take advantage of more than 2GB, and you have to remember that some of your RAM will already be used by background processes in your operating system. When a program needs more memory, your operating system will provide the program with “virtual” memory, which uses free space on your storage drive—if your storage drive is a hard drive, this is especially crippling. 4GB
—Better, of course, but there are quite a few games today that can benefit from up to 4GB. Considering that part of your RAM will already be devoted to other processes, and next-gen games could use even more, 4GB is still not quite ideal. 8GB
—You probably guessed by now, but this is the optimal amount. Enough for games to take full advantage of the available capacity with plenty of room to spare. 16GB and beyond
—For a gamer, this is perhaps overkill. You could call it additional future-proofing, but the most practical use for this amount RAM will be in a workstation environment (Video editing, 3D modeling, and other CPU-intensive applications using larger amounts of data and commands). Buying a two-module 8GB kit today will give you the option to upgrade to 16GB easily if you ever need it.
You should try to fit 8GB into the budget for a gaming system. However, RAM is essentially a commodity and subject to major shifts in price based on supply and demand. Examining the price differences in various RAM kits is a good start in determining at what point you’ll get more for your money. For example, a 4GB kit may cost $11/GB, while an 8GB kit would be at around $7/GB, translating to roughly 50% better “bang for buck.” ====///====How Fast Should it Be?====\\\====
Once you’ve determined how much RAM you want, you’ll encounter a variety of speed choices, ranging from 1333MHz to as high as 3,000MHz these days. The speed, or bandwidth, dictates how quickly the CPU can read the data stored in the RAM. Sometimes, programs that show system information (such as CPU-Z) will indicate 667MHz for 1333MHz RAM, 800MHz for 1600MHz RAM, 933MHz for 1866MHz RAM, etc. This speed represents half the allotted frequency for a single stream. Since your RAM is Double Data Rate, it can send and receive data at the same time at the same speeds, which means 800MHz upstream and 800MHz downstream for 1600MHz DDR3 RAM.
For the sake of keeping this explanation short, I’ll go ahead and tell you that for a gaming PC, the differences in performance will be marginal, and there is no need to spend the extra money for fast RAM. The “sweet spot” is generally 1600MHz and usually has some of the best pricing due to its popularity. In addition, modern unlocked CPUs can support it without issue—meaning, your CPU’s integrated memory controller (IMC), which supports a specific RAM speed natively, will have no trouble with 1600MHz. As you move to 2133MHz and beyond, it’s luck of the draw as to whether your CPU’s IMC will be able to handle it without overclocking your CPU or raising the voltage of the RAM. And the RAM speed just isn’t that important in gaming. ====Timings====
Another element of speed are RAM timings—particularly, Column Address Strobe (CAS) latency, which represents how long it takes from the moment your CPU’s memory controller instructs the RAM to access a particular data set (or memory column) to the moment that data is made available. CAS latency is measured in nanoseconds, so the lower the better. If you’ve ever looked at RAM specifications and saw a set of four numbers (e.g., 9-9-9-24), the first number represents CAS latency. The other numbers represent other delays/timings (with the same rule that lower=better). Again, the differences in latencies are largely negligible. ====Manually Setting RAM Speeds====
It’s important to know that if you choose RAM modules that are 1600MHz or faster, you may need to manually set the speed and timings in your bios, for two reasons:
1. The bios will, by default, run your RAM at the native speed supported by your CPU’s IMC. For example, if you purchase 1600MHz RAM and your CPU is an i7-4670K, your CPU’s IMC supports 1333MHz by default. Any speed higher than that is considered “overclocking.” But as I said earlier, 1600MHz or even 1866MHz won’t be a problem.
2. Speaking of overclocking, most high-speed RAM modules really just use overclocked chips. Depending on the quality of the components used, they may be “binned” to run stable at a speed higher than 1333MHz at a particular set of timings and voltage. Depending on the modules used, your motherboard may recognize them for what they really are, and you’ll have to manually set the RAM’s specifications that are guaranteed for those modules.
Luckily, it’s easy to set your RAM speeds in the BIOS. Just consult your motherboard manual, and do not neglect this important step. It’s alarming how many people with high-speed RAM are actually running it at a rock-bottom 1333MHz simply because they didn’t know to manually set its specifications in the BIOS.
Further reading on memory settings: LINK
This post was edited on 3/20 at 3:40 pm