What type of ddr2

Memory is designed to be backward compatible within its generation, so generally speaking, you can safely add faster memory to a computer that was designed to run slower memory.

However, your system will operate at the speed of the slowest memory module installed. Rather than give memory modules catchy names, the industry refers to modules by their specifications. But if you don't know a lot about memory, the numbers can be confusing. Here's a short summary of the most popular types of memory and what the numbers refer to.

For double-data-rate memory, the higher the number, the faster the memory and higher bandwidth. When referenced by the industry name, the numbers that follow "PC" and the generation refer to the total bandwidth of the module. Optimized for gamers, professional designers, and enthusiasts who need to maximize data rates, DDR4 is for those who want the most from their system. CL refers to how quickly memory column addresses can be accessed.

A lower CL provides faster access than a higher CL. As Figure makes clear, CL values increase when comparing different types of memory. Most, but not all, memory module labels indicate the CL value. However, you might encounter DDR4 memory on the latest desktop and laptop computers. See the following sidebar to learn more.

DDR4 supports densities up to 16Gb per chip twice the density of DDR3 , twice the memory banks, and uses bank groups to speed up burst accesses to memory, but uses the same eight-bit prefetch as DDR3. Both methods depend upon the presence of an additional memory chip over the chips required for the data bus of the module.

For example, a module that uses eight chips for data would use a ninth chip to support parity or ECC. If the module uses 16 chips for data two banks of eight , it would use the 17th and 18th chips for parity refer to Figure Figure A standard unbuffered module top compared to a buffered registered module with ECC bottom. Parity checking, which goes back to the original IBM PC, works like this: Whenever memory is accessed, each data bit has a value of 0 or 1.

When these values are added to the value in the parity bit, the resulting checksum should be an odd number. This is called odd parity. A memory problem typically causes the data bit values plus the parity bit value to total an even number.

This triggers a parity error, and your system halts with a parity error message. Note that parity checking requires parity-enabled memory and support in the motherboard. The method used to fix this type of error varies with the system. On museum-piece systems that use individual memory chips, you must open the system, push all memory chips back into place, and test the memory thoroughly if you have no spares using memory-testing software. Or you must replace the memory if you have spare memory chips.

If the computer uses memory modules, replace one module at a time, test the memory or at least run the computer for a while to determine whether the problem has gone away. If the problem recurs, replace the original module, swap out the second module, and repeat. Some system error messages tell you the logical location of the error so you can refer to the system documentation to determine which module or modules to replace.

Parity checking has always cost more because of the extra chips involved and the additional features required in the motherboard and chipset, and it fell out of fashion for PCs starting in the mids. Systems that lack parity checking freeze up when a memory problem occurs and do not display any message onscreen.

For critical applications, network servers have long used a special type of memory called error-correcting code ECC. This memory enables the system to correct single-bit errors and notify you of larger errors.

The parity bit in parity memory is used by the ECC feature to determine when the content of memory is corrupt and to fix single-bit errors. Unlike parity checking, which only warns you of memory errors, ECC memory actually corrects errors.

ECC is recommended for maximum data safety, although parity and ECC do provide a small slowdown in performance in return for the extra safety. ECC memory modules use the same types of memory chips used by standard modules, but they use more chips and might have a different internal design to allow ECC operation.

ECC modules, like parity-checked modules, have an extra bit for each group of eight data bits. Systems that support parity or ECC memory can use non-parity checked memory when parity checking and ECC are disabled.

Most types of desktop memory modules use unbuffered memory. However, many servers and some desktop or workstation computers use a type of memory module called registered memory or buffered memory : buffered memory is the term used by the exam. Buffered registered memory modules contain a register chip that enables the system to remain stable with large amounts of memory installed. The register chip acts as a buffer, which slightly slows down memory access.

Buffered registered memory modules can be built with or without ECC support. However, most buffered memory modules are used by servers and include ECC support. Figure compares a standard unbuffered memory module with a buffered registered memory module that also supports ECC. Most desktop computers use full-sized memory modules known asDIMMs. Almost all systems can be used with a variety of memory sizes. However, systems that are designed to access two or more identical modules as a single logical unit multi-channel provide faster performance than systems that access each module as a unit.

When two identical same size, speed, and latency modules are installed in the proper sockets, the memory controller accesses them in interleaved mode for faster access. Most systems with two pairs of sockets marked in contrasting colors implement dual-channel operation in this way: install the matching modules in the same color sockets see Figure See the instructions for the system or motherboard for exceptions. Figure To use dual-channel operation on this motherboard, add an identical module to the light-colored memory socket.

Use a matched pair same speed and CL value as the first pair in these sockets for best performance. Most of these systems use two sets of three sockets. Populate at least one set with identical memory. Some triple-channel motherboards use four sockets, but for best performance, the last socket should not be used on these systems. Most of these systems use two sets of four sockets. Populate one or both sets with identical memory. A single-sided more properly known as single-ranked module has a single bit wide bank of memory chips.

A double-sided double-ranked module has two bit banks of memory stacked for higher capacity. Many, but not all, of these modules use both sides of the module for memory.

Refer to Figure The top module is single-sided one bit rank and the bottom module is double-sided two bit ranks , but all of the memory chips are on the front of the module. Some systems, primarily older systems using DDR2 or older memory technologies, have different maximum amounts of RAM based on whether single-sided or double-sided modules are used.

When it comes to memory, compatibility is important. The labels on the memory modules shown in Figure list the manufacturer, module type, size, and speed, and most also list the CAS latency CL value. If you want to buy additional modules of the same size, you can use this information to purchase additional modules. Be sure to have the model number of the motherboard or the model of the computer handy. Some memory vendors, such as Crucial.

This type of utility displays installed memory size and speed. Nevertheless, this is an important skill to learn and understand.

When you install memory, be sure to follow the important safety procedures in exam objective 5. Before working with any memory modules, turn the computer off and unplug it from the AC outlet.

Use an antistatic bag to hold the memory modules while you are not working with them. Before actually handling any components, touch an unpainted portion of the case chassis in a further effort to ground yourself. Try not to touch any of the chips, connectors, or circuitry of the memory module; hold them from the sides.

Step 1. DIMM modules have connections with different widths, preventing the module from being inserted backwards. Step 2.

Verify that the locking tabs on the socket are swiveled to the outside open position. Some motherboards use a locking tab on only one side of the socket. Step 3. The lightweight aluminum exterior and a non-slip silicone cover make the device highly portable and durable.

Combined, these provide superior reliability and endurance nearly equivalent to SLC, yet at a cost-effective price. Reliable speeds and customized functions cater to the requirements of various embedded system applications. Featuring the USB 3. This enables the memory controller to know the exact clock cycle when the requested data will be ready, so the CPU no longer has to wait between memory accesses.

Effectively, it doubles the transfer rate without increasing the frequency of the clock. This is achieved by improved bus signal. They can make the memory control the refresh rate according to the temperature variation. DDR4 adds four new Bank Groups technology. Each bank group has the feature of singlehanded operation. You have already accepted cookies, but you may still revoke your consent at any time. Please see more details at Cookie Statement. Change Settings.