DDR2 Parts Details
Typical module sizes for DDR2 RAM are 512 MB and 1 GB. DIMMs with 256 MB or 2 GB are somewhat harder to find on the market. Uninformed buyers are sure to be confused by the many and varied memory speed designations, shown in the following table.
Additional information about placement of individual memory chips on a module and their organization.
Most memory makers offer precise information about what chips they use in their modules.
The designation: "Chip: 64Mx8" means that individual chips on a module consist of eight 64-megabit memory parts (64 megabits / 8 bits per Byte = 8 MegaBytes or MB = 64 MB total). By extension, each individual chip has a storage capacity of 64 megabits.
The designation: "Module: 128Mx64" indicates that the entire module includes 64 parts, each 128 megabits in size (128 megabits / 8 bits per Byte = 16 MB x 64 parts = 1 GB). If a 1 GB module is composed of 16 individual chips, each chip must therefore have 64 MB of capacity. In this case, we're talking about double-sided modules, because when it comes to large-capacity chips only eight typically fit on each side of a standard memory module.
Typical configurations for desktop DDR2 memory modules are:
|Module Capacity||Sides||Typical Chip Organization|
|256 MB||1||32 MB Chip x 8|
|512 MB||2||32 MB Chip x 8 x 2 Sides|
|512 MB||1||64 MB Chip x 8|
|1 GB||2||64 MB Chip x 8 x 2 Sides|
|1 GB||1||128 MB Chip x 8|