Laptop Parts Expert Blog

Laptop Memory Explained June 8, 2009

For years, I have been asked if memory has to be used in pairs. This seems to be an urban myth now. Back in the early years of PCs, the memory used was call a SIMM, Single Inline Memory Module. When using SIMMs, they had to be used in pairs, usually matching pairs. And the chip type had to be the same in DRAM, you couldn’t mix the standard Fast Page mode with the newer technology called EDO, Enhanced Data Output.

When more advanced CPUs were introduced, new memory types came out with them. The least popular was RAMBUS which I have never seen offered in a laptop, only desktops. The type that was popularized was SDR or Synchronous Data Rate chips. These chips were built on a DIMM or Dual Inline Memory Module. Unlike the RAMBUS chips where every memory slot had to be filled, even with a dummy module, SDR DIMMS could be used one at a time and in mixed densities like 8MB and 16MB together.

As chip technology became more advanced, DDR DIMMS were introduced which ran at Double Data Rate. They can still be used one at a time and they are backward compatible to older speeds.  We are currently in DDR3 now which goes up to PC10600, DDR1333 speeds.

To find the memory that goes in your specific model of laptop go to our website at www.laptoppartsexpert.com.