Laptop computers are designed to support only certain RAM types.
RAM, or memory, is one of the most important components in a computer, and a laptop's RAM directly influences its performance and speed. RAM is present as modules that are attached to predefined slots in the laptop's motherboard. Upgrading RAM will increase memory and enable a laptop to boot up and load programs faster, and to execute instructions more efficiently. In a laptop computer, upgrading RAM entails adding compatible RAM modules.
Specifications
RAM specifications that influence a laptop's performance include CAS (column address strobe) latency time and clock speed. In laptops with AMD processors, CAS latency time is a significant factor because of the processor's integrated HyperTransport technology that is already very efficient, with low latency times. In such laptops, lower latency times directly lead to faster system performance. For laptops with Intel processors, the CAS latency time does not affect system performance as much, and the speed that the laptop is able to execute instructions is determined mainly by clock speed.
Main RAM Types
Even though the technology may be the same, laptop RAM may have different form factors. The most common RAM modules in laptop computers are SO-DIMM, mostly used in standard laptops and notebooks, and Micro-DIMM. In terms of physical attributes, Micro-DIMM RAM modules have smaller dimensions and are more appropriate for more compact devices, such as smaller, ultra-portable laptops.
SO-DIMM
SO-DIMM modules are classified as either DDR or DDR2. DDR is an older technology, and laptops with Celeron M and older Centrino processors are equipped with DDR modules such as DDR 266 PC 2100, DDR 333 PC 2700 and DDR 400 PC 3200. The newer technology, DDR2, is steadily replacing DDR modules and includes module types such as DDR2 400 PC 3200 and DDR2 533 PC 4200, and are mostly used in laptops with Centrino processors. DDR2 offers certain performance enhancements over DDR RAM modules and are also more energy-efficient and less expensive.
Memory Upgrade
Depending on manufacturer and model, a laptop may support one type of RAM modules and not others. When upgrading memory, the replacement modules should be compatible with the motherboard. A laptop's RAM capacity may be increased or upgraded by adding more modules to any vacant slots, or replacing lower-capacity modules with higher-capacity ones. For each model, the manufacturer's website and the user manual may be referred to for information and details on supported RAM modules. If an incompatible type of RAM module is attached, it might damage the module and the motherboard port.
Dual Channel Operation
Some laptops, such as Centrino-based systems running DDR2 memory, are able to operate in dual channel. The feature allows performance benefits by adding more bandwidth to memory and allowing higher data transfer rates. Dual channel operation calls for two identical DDR2 memory modules, running simultaneously. For general users who use their laptops for basic applications such as word processors or web browsers, performance benefits of dual channel memory may be negligible. The enhanced bandwidth is more apparent and can be fully appreciated when running demanding and resource-intensive processes, such as multimedia editing and gaming.
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