Subtitles of the Movie

When we start to take a look at memory, we'll see that there are many different memory types. And pretty much, once we've bought a system board for a computer, the types of memory that we can use on that board have already been determined by the manufacturer. But it's important to understand the different types of memory and the advantages and disadvantages that each one offers. When we talk about memory types, we are going to talk about three different components of memory types. And that is the Form Factor, whether it provides error checking or not, and buffering or registering. There are many different Form Factors. The picture is one of the most common Form Factors called a DIM, and we are going to discuss many different Form Factors. Let's take a look at some of the other Form Factors. Form factors include Extended Data Output or EDO, which is faster because it can do two things at once. Extended Data Output can process at about 60 to 70 nanoseconds. Synchronous Dynamic RAM or SDRAM eliminates the waits by synchronizing itself with the Memory Bus. So as fast as your Memory Bus is, if you have a 66 MHz Memory Bus, then the SDRAM will synchronize itself with that Bus. If you have a 100MHz Bus it will synchronize itself with that, and so on. Double Data Rate Memory supports data transfers at the beginning and the end of each clock cycle. So not just the beginning but also the end of a clock cycle indicates that a data or that memory can be transferred. So this in effect doubles the amount of information that is sent in a given period of time. One of the newer forms of memory is the Direct Rambus, which provides a higher speed memory using a radically different memory architecture. It basically uses a bus in which all of the memory is transferred through a single Bus in sort of a straight-line fashion. So far, direct Rambuses are significantly more expensive than other memory types, but this is likely to change - it could come down. And there is a considerable debate going on right now as to whether Rambus is a superior technology to the fast SDRAM. But only time will tell as to which one will win out. Direct Rambus probably is a faster technology, but it's whether it's worth paying the additional amount for that type of memory. And it depends on how many computers or servers that you are purchasing that for. These are just some of the Form Factors available in memory, and the best ones to know for the test. But for real life, the Form Factor that we use will have already have been determined by the manufacturer. And we can find out a lot about what a system contains and what it can use by going to the manufacturer, the memory manufacturer's website, and many of the memory manufacturer's websites now have a tool which allows us to determine what memory requirements a particular computer would have, and what was already on board when it was bought, and what can be added to it, and in what way the chips need to be added - for example, do we need to buy them, in twos or can we just buy one. So we can only use the types of memory that were already prescribed by the manufacturer when the system was built. That's why it is very important to understand what we are buying when we buy it. Another factor that is important to understand when we buy memory is whether the memory has error checking capability or not. For most workstations, this isn't important, and in most workstations it's not even available. But for most Servers, error checking is a necessity. We will discuss error checking in our next section.