PC3200 is the name for a certain type of computer memory module, named for the speed at which data can be transferred from the module. The designation is important if you'd like to replace or upgrade the memory in your PC or Mac, as only certain computer models are compatible with PC3200 modules.

PC3200 Defined

PC3200 is the common marketing name for a Double Data Rate (DDR) type of SDRAM (synchronous dynamic random access memory) that has an internal clock speed of 200 Mhz. The "3200" refers to the peak transfer speed (in megabytes per second) of the data stored in that module. PC3200 modules are also sometimes referred to as DDR-400 modules.

Compatibility

DDR SDRAM memory modules are used to add memory to a variety of PC and Macintosh models. PC3200 represented the fastest DDR memory prior to the introduction of DDR2 modules. PCs and Macs using PC3200 memory modules were mostly manufactured between 2003 and 2005.

Module Sizes

DDR SDRAM generally comes in two module sizes. DIMM (Dual Inline Memory Modules) are used to add memory to desktop PC and Mac models. SO-DIMMs (Small Outline DIMMs) are used primarily for notebook and some compact or all-in-one computers.

Backward Compatibility

While it's ideal to use a memory module that is speed-matched to your PC or Mac, it's possible to use PC3200 modules in computers that support slower DDR SDRAM modules such as PC2700, PC2100 and PC1600.

DDR vs. DDR2

DDR2 is a later technology and specification that is not backward-compatible with DDR. If you're looking to upgrade a computer that required DDR PC3200 modules, note that PC4000 DDR2 (and faster) modules will not fit a DDR-style upgrade slot.

Source:

Memory Upgrade from Crucial

DDR2 vs. DDR