In lesson 3 we’ll cover RAM memory types, speeds and bandwidths. DDR2 and DDR3 RAM, their advantages and disadvantages, what features and specs to look for when shopping, and how much you can expect to pay.
Your computer’s memory, also called RAM or Random Access Memory, is used to hold the information that the computer is working on. When you power the computer on, it reads all the information needed to start Windows from the hard drive into memory.
Once Windows is loaded, the computer loads any programs or files you open from the hard drive into memory. The reason for this is the computer’s memory, or RAM, is hundreds of times faster than the computer’s hard drive. This allows the computer to perform faster.
The more memory your computer has the more programs and files can be opened at once. For most computers 8GB is more than enough. If you plan to do a lot of picture or video editing you should consider getting 16GB or more of RAM since these types of applications take up more memory than typical programs. The 32bit versions of Windows 7 and Windows 8, can only see 3.5GB of RAM. For this reason you will need to install the 64bit version of Windows. See Lesson 2 of the Computer setup lessons for choosing the 64bit version of Windows. If you are installing more than 16GB of RAM you will need to get the Pro version of Windows as Home or regular versions are limited to 16GB of RAM.
The current standard for RAM is called DDR3. DDR3 is able run at higher speeds and therefore higher bandwidths compared to the previous standard, DDR2.
Types of RAM
There are currently 2 types of RAM used in computers today.
The older type which has been around for 7 years is called DDR2. The newest type which has become the standard for computer is called DDR3. DDR3 is able run at higher speeds and there for higher bandwidths. We go into speed and bandwidth in a moment.
Memory comes in the form of a stick that attaches to the computer’s motherboard through a memory slot. The memory stick is actually made up of several individual memory chips, that when added up, combine to create the storage capacity of the memory stick. Memory sticks come in capacities of 512MB and 1, 2, 4 or 8GB.
For more on motherboards see the motherboard component lesson or the installation lessons.
Speed of Memory
The speed of the RAM is also important. The speed of memory is measured in Mega Hertz or MHz and ranges from 400 MHz to 2000 MHz or 2 GHz and up. Generally, you should get the fastest RAM the motherboard you choose can handle.
Another measurement of RAM speed is called CAS. It’s measured in Nano seconds or ns and comes in speeds of between 7 and 12 ns for DDR3 RAM. A lower CAS is better, but unless you’re building a high end system it’s probably not worth paying extra for the lower CAS.
The name refers to the bandwidth the memory has. So PC3 12800 can move 12800 MB of data per second.
To convert from bandwidth to the speed of RAM, you either multiply or divide by 8. So if you want to find the speed of PC3 12800 RAM, divide by 8 and you get 1600, or 1600 MHz, which is the actual speed of PC3 12800 DDR2 RAM. To go from speed to bandwidth you multiply by 8.
This is useful to know when you’re shopping for RAM and motherboards since some shops list only speed and other shops list only bandwidth. By multiplying or dividing by 8, you can be sure a motherboard can support the RAM you buy.
Dual, Triple and Quad Channel
When you buy RAM for your new computer we recommend you get 2 sticks of DDR3 memory, at least 4GB in size with the same specifications, for a total of 8GB. Since most motherboards have 4 available slots to add memory, you’ll have 2 more slots available for adding memory in the future, should you need to.
The reason for using 2 sticks of memory is so that you can enable Dual Channel on the motherboard. Dual Channel combines the 2 sticks of memory to double their bandwidth and increase the speed at which the RAM is accessed. Intel socket 2011 motherboards support Quad Channel memory which quadruples the memory bandwidth and requires 4 sticks of memory. More on this in a moment.
Dual Channel support is standard on just about every motherboard made today. The motherboard will detect the matched set of RAM sticks and enable Dual Channel automatically. See the installation lesson 2 or your motherboard manual to make sure Dual Channel is enabled.
If you want to add more memory in the future you can add another set of matched memory sticks to keep Dual Channel active.
Intel’s socket 2011 motherboards can use Quad Channel DDR3 memory kits. These motherboards have 4 to 8 RAM slots. If the motherboard has 8 slots you can install 4 RAM sticks and still have 4 more available to add memory in the future and keep Quad Channel enabled.
One more thing about Dual and Quad Channel memory. To make sure the RAM sticks are well matched to each other it’s best to buy kits of RAM that say they support Dual, or Quad Channel configurations. This will ensure the RAM is stable and won’t cause errors or crashes.
If you are planning to try Overclocking the RAM you might also look at the voltage rating of the RAM. Overclocking means running the RAM faster than it’s meant to be run to get more performance. The standard voltage for DDR3 RAM is 1.5 volts and you can find RAM that will run at up to 2 volts.
On Core i7 and i5s using Socket 1150 or 1155 the ram voltage is limited to 1.6v and on Core i3 CPUs the ram voltage is limited to 1.5v. And on Core i7 cpu’s using Socket 2011 the ram voltage is limited to 1.85v.
If you are planning to try Overclocking the RAM you might also look at the voltage rating of the RAM. Overclocking means running the RAM faster than it’s meant to be run to get more performance. The standard voltage of DDR2 RAM is 1.8 volts and you can find RAM that will run at up to 2.4 volts. The standard voltage for DDR3 RAM is 1.5 volts and you can find RAM that will run at up to 2 volts.
With Intel’s 1st generation Core i7 cpu’s the ram voltage is limited to 1.65v. On second generation Core i7 and i5s the ram voltage is limited to 1.6v and on Core i3 CPUs the ram voltage is limited to 1.5v.
To overclock the RAM you’ll be increasing its speed using settings in the motherboards BIOS and upping the voltage of the RAM to keep the system stable and working. See the Overclocking video lessons on the website for instructions on how to overclock your RAM. Keep in mind that overclocking the RAM will increase heat so look for ram with built on heat sinks, also called heat spreaders, if you plan to overclock the RAM.
When you purchase your computer’s memory, look for:
- 2, 4GB, as a minimum, DDR3 sticks in a package to enable Dual Channel on the motherboard.
- and if the motherboard you’re using support Quad Channel memory, get a minimum of 4, 2GB DDR3 sticks in a package.
- Get the fastest MHz memory the motherboard you choose can handle.
- Buy the lowest CAS RAM you can afford and look for higher voltage support if you plan to Overclock the RAM.
In the installation lessons we’ll show how to install RAM, processor and CPU cooler onto the motherboard.
Computer memory is generally very reliable and will last for many years. That said, it’s best to buy memory with at least a 1 year warranty.
Generic RAM typically comes with a 90 day warranty. Branded RAM (Corsair, Kingston, etc.) will come with a 1 to 3 year warranty.