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In this video we are going to learn more about the different types of memory, speed and bandwidth and how they relate to each other, other features of memory you need to know about to make sure you get the correct memory for your system and we’ll show you another tool to help you identify the memory in your system.
Types of RAM and Identifying them
Lets begin by going over different types of memory and how they are identified in stores and online. In Lesson 1 we listed RAMBUS, DDR, DDR2 and DDR3 as the 4 different types of memory in use since 2000.
RAMBUS memory was in use from 2000 to 2004. It can be referred to as RDRAM and is usually listed as PC and then a number with no space in between. The numbers indicate the RDRAM’s effective speed in MHz and ranges from PC(600MHz) to PC(1200MHz).
DDR memory was in use from 2000 to 2004. It can be referred to as DDR-RAM and is usually either listed as DDR, space, and a number or PC, space, and a number. For example when listed as DDR 400 the number, 400 in this case, refers to the speed in MHz.
The same memory can be listed as PC, space, 3200. The 3200 refers to the bandwidth the memory has, measured in MB/s. Because some stores list only speed and some list only bandwidth its useful to know how to convert between the two ways of listing the same memory. We’ll show how in a few moments, after we cover DDR2 and DDR3 memory.
DDR2 memory has been in use since 2004. It can be referred to as DDR2-RAM and it is usually either listed as DDR2, space, and a number or PC2, space, and a number. For example when listed as DDR2 800 the number, 800 in this case, refers to the speed in MHz.
The same memory can be listed as PC2, space, 6400. The 6400 refers to the bandwidth the memory has measured in MB/s.
DDR3 has been in use since 2007. It can be referred to as DDR3-RAM and it is usually either listed as DDR3, space, and a number or PC3, space, and a number. For example when listed as DDR3 1066 the number, 1066 in this case, refers to the speed in MHz.
The same memory can be listed as PC3, space, 8500. The 8500 refers to the bandwidth the memory has measured in MB/s.
For DDR, DDR2 and DDR3 some shops list only speed and some list only bandwidth. You can convert from speed to bandwidth and back using a simple method. You either multiply or divide by 8. Take, for example, DDR3 800 memory. You can multiply 800 by 8 and you get 6400 or 6400MB/s which is the bandwidth of DDR3 800 memory. To convert from bandwidth to speed you divide by 8.
Other Features of Memory
Now that we know about the different kinds of memory and how speeds and bandwidths relate to one another, lets go over some other features of memory you need to know about. How many channels the memory is operating on is very important to know. It can be single, dual or triple channel. In single channel mode each memory stick runs at it’s own bandwidth. If you have for instance a PC2 6400 stick of memory it’s bandwidth is 6400MB/s. More bandwidth means better performance.
Dual Channel
In dual channel mode you can have 2 or 4 sticks of memory combining their bandwidth. So two sticks of PC2 6400 memory would become the first channel of memory and combine to make 12800MB/s of memory bandwidth. If you add another 2 sticks of PC2 6400 RAM to the system they would become the second channel of memory and combine to make another 12800MB/s of memory bandwidth.
Single channel is when your computer has 1 stick of memory or 2 sticks of memory just not in the correct memory slots. Dual channel can be activated if the computer has 2 or 4 sticks of memory. I say, can be activated, because the memory sticks have to be in certain slots on the computers motherboard. Which slots to use to activate dual channel mode depends on the motherboard. You have to look this up in the motherboard’s or computer’s manual or ask the computer maker to be sure.
Triple Channel
Triple channel is available on higher end Intel Core i7 systems that use the socket 1366 CPU interface and requires 3 or 6 sticks of memory. Using triple channel mode, triples the memory bandwidth. Like Dual channel, for the memory to run in triple channel mode the sticks of memory need to be installed into the correct memory slots on the motherboard.
Memory Timings
Memory Timings or CAS Latency, which is usually shown as CL= and a number is another measurement of speed. Its the time in nano seconds the memory waits between each operation. A lower number is better and more expensive. However the memory will run at the slowest CAS speed of any memory stick in the system. So if you have CL=9 memory and you add CL=7 memory memory it will run at CL=9 speeds. We’ll show you how to find what your memory’s CAS Latency is in a moment.
Duration : 0:9:49
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