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When it comes to memory, compatibility is important. The memory module type must fit the motherboard; speed must be compatible and the module storage size/combination must match your computer system as well. A DIMM's capacity and other operational parameters may be identified with serial presence detect (SPD), an additional chip which contains information about the module type and timing for the memory controller to be configured correctly. The SPD EEPROM connects to the System Management Bus and may also contain thermal sensors ( TS-on-DIMM). [12] Error correction [ edit ] Standardized Dimensions: The dimensions and pin configurations of SODIMMs are standardized by JEDEC, the organization that develops standards for the microelectronics industry. Are DDR, DDR2 and DDR3 SO-DIMM memory modules interchangeable?". acer.custhelp.com . Retrieved 2015-06-26.
Like desktop DIMMs, SODIMMs have also increased the number of pins over time. SDR SODIMMs had 144 pins, while DDR and DDR2 used 200 pins. DDR3 upped the pin count to 204, while DDR4 increased that to 260 and DDR5 to 262. This further ensures electrical incompatibility between generations of SODIMM memory. Where Are SODIMMs Used? RAM is used for programs and data as well as by the operating system for disk caching (using RAM to hold recently accessed information). Thus, installing more RAM improves transfers between the CPU and both RAM and hard drives. If your computer runs short of RAM, the operating system can also use the hard drive as virtual memory, a slow substitute for RAM. Although the hard drive can substitute for RAM in a pinch, don’t confuse RAM with mass storage devices such as hard disks or SSDs. Although the contents of RAM and mass storage can be changed freely, RAM loses its contents as soon as you shut down the computer, while magnetic storage can hold data for years. Although RAM’s contents are temporary, RAM is much faster than magnetic or SSD storage; RAM speed is measured in nanoseconds (billionths of a second), while magnetic and SSD storage is measured in milliseconds (thousandths of a second). RAM Types—This section provides the information you need to understand memory chip and module types and how some types of memory are designed to correct memory errors. Fulton, Jennifer (November 9, 2000). "The complete idiot's guide to upgrading and repairing PCs". Indianapolis, IN: Alpha Books – via Internet Archive. Single-Sided vs Double-Sided—Learn what these terms mean and how they might affect how much RAM you can install on a particular system.The small volume of the SODIMM form factor makes them ideal for use in computers with unusually constrained space. As you might have gathered from the intro, SODIMMs are primarily used in laptops. Not all laptops use SODIMM memory, though. As much as it is convenient for users that want the option to upgrade RAM in the future. It’s slightly more complex and expensive to implement than simply soldering the RAM chips directly onto the motherboard. Similar to what you would see on a mobile phone. Look for the “Form Factor” to know your module’s size. View the memory module’s form factor in Task Manager Ilya Gavrichenkov. "DDR2 vs. DDR: Revenge gained". X-bit Laboratories. Archived from the original on 2006-11-21. DDR2 SDRAM was first produced by Samsung in 2001. In 2003, the JEDEC standards organization presented Samsung with its Technical Recognition Award for the company's efforts in developing and standardizing DDR2. [1]
Some small form factor motherboards may use SODIMM slots rather than full DIMMs. The Nano-ITX motherboard standard also includes a SODIMM slot rather than a full-sized DIMM slot. Some upgradeable office printers, routers, and NASs may also use SODIMM slots. However, this would be compared to soldering the memory chips to the motherboard rather than using full-sized DIMMs. Capacity Issues User Upgradeable: Many laptops and SFF machines have user-accessible memory slots, making it relatively straightforward to upgrade the memory by replacing or adding SODIMMs. DDR5 was introduced in 2021, and is the most recent generation of memory technology, marking a revolutionary jump in architecture. It’s arguably the biggest jump in memory technology we’ve seen since SDRAM.DIMMs started out with a 100-pin configuration – the copper connectors you see toward the bottom of the modules. However, due to the advancements in technology and the different DDR types, the DIMM modules now have 288 pins in a DDR5. SODIMM
Like the DIMM form factor, no generation of SODIMM form factored RAM is compatible. This is because the form factor is essentially the only difference between DIMM and SODIMM. There aren’t any performance impacts beyond increased thermal constraints and physical capacity limits inherent to the smaller form factor. Optionally implement ECC, which is an extra data byte lane used for correcting minor errors and detecting major errors for better reliability. Modules with ECC are identified by an additional ECC in their designation. PC2-4200ECC is a PC2-4200 module with ECC. An additional P can be added at the end of the designation, P standing for parity (ex: PC2-5300P).Depending on the specific module and motherboard chipset combination, PC133 modules can sometimes be used on systems that are designed for PC100 modules. DDR SDRAM To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency. JEDEC decided that the terms "dual-sided", "double-sided", or "dual-banked" were not correct when applied to registered DIMMs (RDIMMs). SODIMMs started out with 144 pins, but now have a 262-pin configuration in a DDR5 module. MicroDIMM
For use in computers, DDR2 SDRAM is supplied in DIMMs with 240 pins and a single locating notch. Laptop DDR2 SO-DIMMs have 200 pins and often come identified by an additional S in their designation. DIMMs are identified by their peak transfer capacity (often called bandwidth). https://www.google.com/books/edition/The_X86_Microprocessors_Architecture_And/zWrZY1OgTPsC?hl=en&gbpv=1&dq=dimm+simm+ram&pg=PA576&printsec=frontcover DDR2's bus frequency is boosted by electrical interface improvements, on-die termination, prefetch buffers and off-chip drivers. However, latency is greatly increased as a trade-off. The DDR2 prefetch buffer is fourbits deep, whereas it is twobits deep for DDR. While DDR SDRAM has typical read latencies of between two and three bus cycles, DDR2 may have read latencies between three and nine cycles, although the typical range is between four and six. Thus, DDR2 memory must be operated at twice the data rate to achieve the same latency. After a memory word is fetched, the memory is typically inaccessible for an extended period of time while the sense amplifiers are charged for access of the next cell. By interleaving the memory (e.g. cells 0, 4, 8, etc. are stored together in one rank), sequential memory accesses can be performed more rapidly because sense amplifiers have 3 cycles of idle time for recharging, between accesses.Computer memory module Two types of DIMMs: a 168-pin SDRAM module (top) and a 184-pin DDR SDRAM module (bottom). The SDRAM module has two notches (rectangular cuts or incisions) on the bottom edge, while the DDR1 SDRAM module has one. Also, each module has eight RAM chips, but the lower one has an unoccupied space for the ninth chip; this space is occupied in ECC DIMMs. Three SDRAM DIMM slots on a ABIT BP6 computer motherboard Apart from the distinctive size and cuts on a module, you can also determine what form factor RAM module is installed on your Windows PC without opening it up. Here is how:
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