DDR1 Versus DDR2 Notebook Memory

DDR2 SODIMM – Technical Background

DDR2 SODIMMS for notebook-pc’s offer a number of improvements over the previous DDR1 generation memory solution. These include a space-saving form factor, low power consumption, improved thermal characteristics, and high bandwidth. All this results in greater performance per watt and improved battery life compared to other memory standards.

Let’s start out by looking at the above image and noting that the DDR2 module (on the right side) has a shorter profile than the DDR1 modules on the left. While the width is exactly the same the decreased height of the module will offers two distinct benefits for the chassis. Meaning that the smaller modules will allow for the advancement of smaller/lighter notebooks and better airflow, which is something all notebooks can’t have enough of.

Just like desktop memory DDR1 and DDR2 memory can not be used on the same DIMM slots due to an alignment change in the PCB. In the image above we sat a Kingston DDR2 module over a DDR1 module and although the pin count is the same the slot alignment differs just enough to make sure you can’t use the wrong modules when you build or upgrade your notebook memory.

Previous generation DDR1 notebook memory modules ran at PC-2700 (333MHz) at 2.5V or 2.6V depending on what IC’s are used on the modules. Most TSOP based DDR1 modules were set to run at 2.6V while micro-BGA ran at 2.5V due to lower power consumption. Desktop Computers with DDR1 PC-3200 (400MHz) modules had a suggested voltage of 2.7 Volts, so notebook memory was power hungry to say the least. DDR2 notebook SODIMMS are rated at 1.8 Volts, which is nearly a full Volt (0.8V) lower than DDR1 SODIMMs and feature IC’s based on the FBGA process. Our Kingston 512MB PC-2700 module pictured on top was built on the 32MB x 16 configuration and the new 512MB PC2-4300 modules are built using the 64MB x 8. This means that notebooks with DDR2 modules require up to 65% less voltage than those running DDR400, thus improving battery life. Samsung, a leading semiconductor manufacturer, ran internal tests and showed that a notebook PC equipped with Samsung DDR2 memory lasted close to 10% longer before requiring recharging.

The majority of white collar federal government and fortune 500 companies have entrusted their employees with notebooks (why let them work 8 hours, when the can take it home and work 24 hours) with the hope that a notebook will come out that can last a full work day on just the battery. Notebooks with DDR2 memory bring this goal a step closer as the extra 10% battery life can improve mobility and thus productivity. While this is not a huge improvement changes like this are all that can be till fuel cell notebook technology advances.

For the die hard technical junkies please note that DDR2 SODIMMs, just like DDR2 SDRAMs adhere to JEDEC’s DDR2 specifications by adding core functions that include: off-chip-driver calibration to maintain optimal driver strength; on-die termination for maximum signal integrity; and posted CAS, a command control method to enhance bus efficiency. So far Legit Reviews has not seen any consumer notebooks that have adjustable memory timings. While enthusiasts and gamers have known for years that tighter timings on desktop applications are faster early this year when we tested different timings in out DDR1 notebook a tight timings did not make a big difference in our situation.