DDR Memory Modules

I've recently had to learn a bit about memory modules to figure out what's going to be compatible with a motherboard I have.

The DIMMS that I tried first were 2 x 1GB sticks. They have a sticker on them that refers to the module, and reads

PC3200 DDR SDRAM 128Mx64 1GB

This is the module configuration; the configuration of the DIMM as a whole. There are 16 chips on the module, 8 on each side, and each chip is marked 64x8. This is the chip configuration.

The chip configuration 64x8 refers to it having around 64 million addressable locations of 8 bits per location. Therefore, each chip contains 64MB (megabytes) of storage.

There are 16 chips on the module, so 64M * 16 is 1024M as we'd expect.

The module configuration description of 128Mx64 states that the chips are combined on the module in such a way that there's a linearly accessible range of 128M locations of 64 bits per location. Therefore, there will be 2 ranks on this module (since the 64 bit data-width is satisfied by 8 chips * 8 bits per chip), typically 8 chips on each side forming a rank.

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-Share Alike 2.5 License.