Are there different types of ddr ram

However, older memory module types such as early pin DIMMs were available with different types of memory chips. You need to specify the right memory chip type in such cases to avoid conflicts with onboard memory and provide stable performance. Memory module speed PC, PC, PC, and so on —There are three ways to specify the speed of a memory module: the actual speed in ns nanoseconds of the chips on the module 60ns , the clock speed of the data bus PC is MHz , or the throughput in Mbps of the memory for example, PC is 3,Mbps or 3.

The throughput method is used by current memory types. Memory module latency —Latency is how quickly memory can switch between rows. Modules with the same speed might have different latency values.

All of the modules in a bank should have the same latency as well as size and speed. Although parity-checked memory mainly slows down the system, ECC memory can detect memory errors as well as correct them. If a system is performing critical work such as high-level mathematics or financial functions or departmental or enterprise-level server tasks , ECC support in the motherboard and ECC memory are worthwhile options to specify.

Some systems also support buffered registered or nonregistered modules. Buffered more commonly known as registered modules are more reliable but are slower because they include a chip that boosts the memory signal. Allowable module sizes and combinations —Some motherboards insist you use the same speeds and sometimes the same sizes of memory in each memory socket; others are more flexible. To find out which is true about a particular system, check the motherboard or system documentation before you install memory or add more memory.

The number of modules needed per bank of memory —Systems address memory in banks, and the number of modules per bank varies according to the processor and the memory module type installed. If you need more than one module per bank, and only one module is installed, the system will ignore it.

Systems that require multiple modules per bank require that modules be the same size and speed. Whether the system requires or supports multi-channel memory two or more identical memory modules accessed together instead of one at a time —Dual-channel memory, triple-channel memory, and quad-channel memory are accessed in an interleaved manner to improve memory latency the time required between memory accesses. As a result, systems running dual-channel memory offer faster memory performance than systems running single-channel memory.

Intel introduced triple-channel memory which runs even faster than dual-channel memory with its Core i7 processor. Quad-channel memory, available on some high-performance Intel desktop and server platforms and AMD server platforms, is even faster. Almost all of these systems can run albeit with reduced performance if non-identical memory modules are used. The total number of modules that can be installed —The number of sockets on the motherboard determines the number of modules that can be installed.

Very small-footprint systems such as those that use microATX or Mini-ITX motherboards often support only one or two modules, but systems that use full-size ATX motherboards often support three or more modules, especially those designed for multi-channel memory two or more modules accessed as a single logical unit for faster performance. DRAM requires frequent recharges of memory to retain its contents.

Memory refreshing is common to other types of RAM and is basically the act of reading information from a specific area of memory and immediately rewriting that information back to the same area without modifying it. Depending on the specific module and motherboard chipset combination, PC modules can sometimes be used on systems that are designed for PC modules. Latency is a measure of how long it takes to receive information from memory; the higher the number, the greater the latency.

DDR3 also has an eight-bit prefetch bus. Although DDR3 modules also use pins, their layout and keying are different than DDR2, and they cannot be interchanged. PC3- indicates the module uses DDR3 memory. Memory modules of the same type with the same speed memory chips can have different CAS latency CL values. 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. Memory technology continues to develop. Each successive generation is faster and uses less energy.

Memory must be compatible with the other components in a computer system. Generally, components are created to the highest standard at the time of manufacture, but with the expectation that technology will continue to change.

To prevent users from inserting incompatible memory, modules are physically different for each memory technology generation. These physical differences are standard across the memory industry. One of the reasons for industry-wide standardization in memory is that computer makers need to know the electrical parameters and physical shape of the memory that can be installed in their computers.

Because the electrical parameters are different for each generation of memory, the physical shape of the memory changes to prevent the wrong memory from being installed in a computer. Computers can use only the generation of memory that they are designed for. The numbers that appear after "DDR" and the generation indicator are the data transfer rate per second of the module.

Please note that hertz is a measure of cycles per second, not the measure of the speed of the cycles. There is also an industry name that indicates the theoretical bandwidth of the module, for example "PC". Bandwidth is calculated by taking the transfers per second and multiplying by eight DDR3 transfers data on a bus that is 64 bits wide, and because a byte is eight bits, this is eight bytes of data per transfer.

If you want to upgrade your computer's memory or build your own computer, you must ensure that the memory is compatible with the other components in your computer. You must choose the correct memory technology before you can look at speed or any other features. Read about how to install more memory in your computer. August 30, In this type of RAM, data is stored using the state of a six transistor memory cell.

It is a type of RAM which allows you to stores each bit of data in a separate capacitor within a specific integrated circuit. Dynamic RAM is a standard computer memory of the many modern desktop computers. This type of RAM is a volatile memory that needs to be refreshed with voltage regularly.

Else it loses the information stored on it. Fast Page Mode Dynamic Random Access Memory is a type of RAM that waits through the entire process of locating a bit of data by column and row and then reading the bit before it begins on the next bit. Max transfer rate is around Mbps. It has access times between 25 and 10 ns nanosecond , and they are in DIMM dual in-line memory module modules of contacts. It generates much more heat as they operate at such high speeds.

Flash memory is an electrically erasable and programmable permanent type of memory. It uses a one-transistor memory to store a bit.