There are a ton of options when it comes to system memory. From data rates to latencies to voltages, the number of combinations can become overwhelming. The easiest answer in the debate of what kit to buy sounds deceptively simple: just buy 1.5-volt DDR3-1600 (PC-12800) modules with CAS 9 timings. All Socket AM3+, FM2+, LGA 1150, and LGA 2011 processors are designed to support at least this memory speed. It's inexpensive as both 4 and 8 GB sticks, and it’s available in both dual- and quad-channel kits.
Yet there are noticeable performance benefits for similarly-priced DDR3-1866 (PC3-14900), particularly if you're using a CPU's on-die graphics engine for gaming. And this speed functions normally, even with processors that are not officially designated to use it (primarily older models or low-energy platforms). And the same easy benefits of DDR3-1866 are even available with most DDR3-2133 kits and modern performance-oriented processors.

The problem with recommending faster memory kits is that they often require at least some manual configuration. If you're not comfortable tooling around in your motherboard's firmware, they might actually drop you to lower performance levels.
You see, Intel’s XMP (eXtreme Memory Profiles) technology facilitates extended memory settings beyond the basic automatic-configuration technology called SPD. Though XMP originally allowed motherboards to set overclocked options like nonstandard voltages and data rates, most of today's XMP-capable modules operate at standard voltage levels and frequencies. Still, when you first boot up, they typically default to either DDR3-1333 or -1066. Going higher requires that you manually enable an XMP profile. Even some DDR3-1600 modules employ XMP (rather than SPD values) to achieve their rated performance levels, and this is particularly true of reduced-latency (CAS 7, CAS 8) modules.
Memory faster than DDR3-2133 is usually expensive and not really required. Our tests have shown that DDR3-2400 is barely beneficial, and only in situations where you're leaning on integrated graphics. We've even seen data rates above 2400 MT/s hurt performance as the motherboard attempts to increase stability.
In terms of memory quantity, Tom's Hardware recommends at least 4 GB for the cheapest Web surfing Windows-based systems. Gamers could probably get by with 4 GB, but we’re more comfortable with the 8 GB that has become the norm in high-performance machines. Few applications push memory needs past that point, though users of memory-intensive programs who also multi-task (such as Tom’s Hardware editors) can occasionally find an excuse to install even more. Users who need more than 8 GB usually know their needs in advance, based on experience with a previous machine.
Even those exceptional circumstances only push us to 12 GB, though 16 GB is easier to install in dual-channel mode (via two 8 GB modules). If you’re desperate for an excuse to add even more, installing RAM disk software (which uses some of your system memory as a virtual hard drive) could be your impetus.

Our memory reviews show a wide range of options, and buying name-brand modules with lifetime warranties from reputable venders is good insurance against unexplained system instability.
- Step One: Size Up A Case
- Step 2: Select Your CPU
- Step 3: Select Your Graphics
- Step 4: Select A Motherboard
- Step 5: Select Memory
- Step 6: Select Storage
- Step 7: Select A Power Supply
- Other Components
- Step 8: Choose Your Vendor
- Step 9: Preparing For Assembly
- Step 10: Build The Platform (CPU, Cooler, And DRAM)
- Step 11: Install Motherboard And Power Supply
- Step 12: Install Cables, Cards, And Drives
Cheers!
Cheers!
Wonderful as usual toms.. Appreciate it..
Great article! No doubt this is going to help a lot of folks.
Thanks, guys!
I think you missed a section for "SLI - XFire", but it's great overall. Since its a guide for folks with little to no knowledge, I think it would help them to dispel myths and get some facts over XFire and SLI.
Cheers!
First I put the motherboard into the PC (not fastened) to see where the standoffs are going to be placed onto the case. Also I note what routes I'm going use for my cabling. Then I take the motherboard out and insert the standoffs and port plate into the case. Also I take my case cables (power sw, reset sw, USB, front audio and mic cables and put a twist tie around them all and place them near where they are to be plugged into the motherboard. These cables are easy to lose track of.
Next I place the power supply, and "bay devices" (optical drives, non-removable storage, etc) into the case and have those cables attached and either hanging over the outside of the case or routed behind the motherboard tray. This obviously depends on how you determined the cables will be routed earlier.
Then I take my motherboard, put the CPU, RAM, and cooling system on as much as I can. Then I place the whole thing into the case - usually at an angle at first, leading with the side with the RAM (which is normally going behind the case bays in smaller cases) in first.
At this point it's just a matter of aligning the motherboard with the standoffs and port plate. Plug it all in (including the case plugs which are conveniently out of the way and together).
Power it all on and volia!
Otherwise, it was a good article. People who are uncertain of building their own PCs can learn a lot from it.
The 647W is measured at the wall socket, as the article mentions input power. After taking into account the 85% efficiency of their power supply in this example, the PSU is only outputting 549.95W to the PC components at max load. Adding some headroom they come to the 600W PSU recommendation.
Personally I'd like a little more headroom, but the calculations in the article are correct.
Building your own is great fun, and most serious users should probably give it a try at least once in their lives. Given that, I'd recommend an annual "refresh" of this article, with updated info and re-validated links to corresponding reference articles and resource forums.
A great service to your readers!
I wanted to comment on the power supply part of the article. One is the efficiency and the total cost to use versus the front end purchase cost. A less efficient system will obviously create more total heat as wasted energy. But aside from possibly making someones room rather uncomfortable, it also increases your airconditioning energy use. A good rule of thumb is that an AC system will use 50% of the heat energy. To add the total annual cost, multiply that times the percentage of the year that the AC is on. So your example of a 647W system with 85% PSU would give (550W used):
647W - 550W = 93W at plug
93W * 50% = 47W AC energy
Total Energy (summertime) = 93W + 47W = 140W
If the AC were on the while year and the PC were on continuously, this is about $140 annually, or almost $12 per month added electricity in the summer. If you did the same thing with a cheap 70% efficient system, you get $248 annual cost which is $20.63 per month summertime cost. At a difference of $8, it does not take many months (of continuous on!) to make the more efficient PSU make much more sense.
The other topic I wanted to comment on is ESD. I am an engineer and work with ESD issues everyday. It is a very real an poorly understood issue by many because of the often hidden or delayed failures that it causes. ESD many time causes walking wounded damage without an immediate failure, which finally fails several months later. And if you look at websites sell PC parts, many people complain of DOAs. Many, many DOAs are caused by ESD. Memory, CPUs, motherboards, HDDs, and other sensitive systems are often returned as DOA, driving up the cost of the PC enthusiast market and adding frustration. In research texts, they estimate the global electronic failures due to ESD to be 40-60% of the total failures over product life.
So that little $5 ESD wrist strap is money well spent. Buy one and reduce your heartburn.
Charles
So that little $5 ESD wrist strap is money well spent. Buy one and reduce your heartburn.
Charles
The only problem with wrist straps is that most people don't want to be "tied" to anything. They're a great idea that's really rarely needed. Feel free to say otherwise if you live in the desert.