In this article we're going to discuss, first off, how to determine what kind of memory your computer uses and how to decide what to buy to fit your needs.
Unfortunately, not all computer memory is alike and the make of your motherboard will determine what memory you will need to get if you want to upgrade or even just replace a defective memory chip.
The first problem is knowing what type of memory you need. Actually this isn't too hard to determine. The user manual that came with your computer should specifically list the kind of memory you have to buy either for upgrade or replacement. If not, you can find this information in the memory advisor tool that came with your operating system.
Then there is the issue of how much to buy. This isn't as easy as it would appear on the surface. Most people would think that they should just get as much as possible. Buy the largest chip sizes that they make and as many of them as there are slots in your motherboard for them. The problem is that every computer has a maximum amount of memory that it can handle. Again, this should be documented in the user manual. If not, you will have to contact the manufacturer or go to a computer tech to have him go over your system. If you put too much memory in your system you are going to run into serious problems. The computer may malfunction or simply not work at all.
Aside from amount of memory, you also have to buy memory that matches the speed of your system. The types of memory speeds are numerous. There's DDR2 or Double Data Rate Second Generation Memory; SDRAM and DDR, which are Double Data Rate First Generation; and then for some of the older systems, which are still in use today, you have SDR and SDRAM which are Single Data Rate chips. And all of these chips come in a variety of speeds. Your system is designed to handle only one of these speeds. So, if you put in a memory chip of a higher speed, your computer will only run it at the maximum speed the system is capable of and buying a faster speed chip is just wasting your money.
The next question is if you need error checking when buying a chip. Most computers have non-parity memory and do not need error checking in their chips. However, if you have a computer with parity memory then you will need error correction code (ECC) or parity modules. ECC modules look for errors in the data. These modules are mostly found in servers and what are called mission critical systems. You can tell which type of module you have in your system, parity or non-parity, by counting the RAM chips in the module. If the number of chips can be evenly divided by three or five then that means you have parity modules and should buy ECC chips. If the number of chips is not evenly divisible by three or five then you should buy non-parity chips.
By following these simple procedures you should have no trouble getting the right type of memory for your system.
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Michael Russell
Your Independent guide to Computer Memory
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