This little guide is to let people know some of the differances in computer memory.

There are many differant type and makers of computer memory modules. Many of the manufactures of these memory modules use the same chips that are found on their compatitions modules, therefore name brand modules are not of much more quality than that of lesser known compaines, which means you can have a name brand and a generic brand in the same computer without any problems.

Even if a memory chip is compatible with your system doesn't mean it will always work. If you get one that doesn't work in you system, it may still work in another.

If you are looking for DDR memory (Double Data Rate) here are some things to remember.

1. Make sure that you are getting it with the right pin count.

2. DDR-400 for example will only have a frequency of 200 not 400 if your system is not set up properly, most systems require you to have 2 modules in before your system will operate at DDR. Your system will not operate DDR with 1 or 3 modules in it. Because of this limitation it is better if you have two 256MB modules in your system instead of one 512MB module.

3. A 256MB PC-3200 DDR-400 184-pin Module for a PC is the same as the one for an iMac.

4. Watch out. There are many companies that charge you over $15 for standard shipping. Believe it or not USPS Priority Mail Flat rate boxes are half this price and if you can get 70 lbs in them it is still $7.60, if you use just a standard box by weight a memory module is less than $6.00, either way you get your item in 2-3 days after it ships.

5. Beware of crooks. There are people and companies the will sell an item for like $.99 with a $70.00 Shipping fee. This is against eBay's policies. These people are trying to get over on paying their selling fees. If you see any of these listings report them. It's sellers like these that make fees go up.

I hope this little bit of information helps.

Good Luck and Happy eBaying.