This is the third article in a series about upgrading a PC (Part one: Preparation, Part two: Graphics Technology). In the article series and accompanying videos, we have taken a five year old PC and one component at a time, stripped the case of the hardware, discussing the differences between that old hardware and what there is to choose from right now. In this edition we take a look at RAM, hard drives and optical drives. RAM Random Access Memory (RAM) holds information temporarily as it is shared between a system’s processor, GPU hard drives etc. 
The modules in our old PC are all DDR1 ECC memory, 512MB modules. The first thing to note is that DDR modules can’t be used in DDR2 motherboards and DDR2 modules can’t be used in DDR3 motherboards (etc). The slots are physically different on the different types of RAM. 
The photo above shows a DDR module above a DDR2 module above a DDR3 module. At the bottom of each module is a small hole or key in the connector. The industry changed the position of the keys on all the different memory types to prevent you from making a mistake since there is not only a physical difference between the types but a voltage difference as well. They also have different bandwidth minimums. The maximum data transfer rate has obviously improved with each iteration of DDR.
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Memory Type
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Maximum Bandwidth
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Highest Memory Speed
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DDR
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3200 MB/s
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DDR400
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DDR2
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8533 MB/s
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DDR1066
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DDR3
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12200 MB/s
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Not reached yet
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When you are choosing RAM, you don’t necessarily have to go for the peak bandwidth RAM. If it has a very high latency then that’s not such a good thing. You can have a high speed RAM like DDR2 1066 but if it’s got really terrible latency timings on it, it might not be as fast as lower speed RAM. RAM timings is a very complicated issue but the decision about RAM modules can easily be simplified if you understand the brandings of a major manufacturer.
Corsair make a few different types of RAM modules, Value Select and their XMS or Pro series. The major difference between the two is that apart from the actual bandwidth speed capabilities, the timing speeds are different. The more professional levels of RAM will not only allow you to run stably at standard speeds but will allow you to overclock the speed of the RAM and adjust the timings to be more aggressive.
Also notice that some enthusiast RAM may require higher voltages than industry defaults. The modules are able to handle these higher voltages thanks to the addition of heatsinks on the modules. I would genuinely recommend standard brand RAM, ie. Corsair Value Select for the average user.
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