Multichannel memory architecture
In the fields of digital electronics and computer hardware, multi-channel memory architecture is a technology that increases the data transfer rate between DRAM memory and the memory controller by adding more communication channels between them. Theoretically, this multiplies the data rate exactly by the number of channels present. Dual channel memory uses two channels. The technique dates back to the 1960s and was used on the IBM System/360 Model 91 and the CDC 6600.
Modern high-end desktop and workstation processors, such as the AMD Ryzen Threadripper series and the Intel Core i9 Extreme Edition line, support quad-channel memory. AMD Epyc series server processors and Intel Xeon platforms support memory bandwidth from the four-channel module design to the eight-channel design. In March 2010, AMD released the processors in the Socket G34 series and Magny-Cours Opteron 6100 with support for four-channel memory. In 2006, Intel released chipsets supporting four-channel memory for its LGA771 platform and later in 2011 for its LGA2011 platform. Microcomputer chipsets with even more channels were designed; for example, the AlphaStation 600 (1995) chipset supports eight-channel memory, but the machine's backplate limits operation to four channels.
Dual channel architecture
Dual channel enabled memory controllers in a PC system architecture use two channels of 64-bit data. Dual channel should not be confused with double data rate (DDR), in which data exchange occurs twice per DRAM clock. The two technologies are independent of each other, and many motherboards use both when using DDR memory in a dual-channel configuration.
Operation
Dual-channel architecture requires a dual-channel capable motherboard and two or more DDR, DDR2, DDR3, DDR4, or DDR5 memory modules. Memory modules are installed in matching banks, each of which belongs to a different channel. Your motherboard manual will provide an explanation of how to install the memory for that particular drive. Typically, a matched pair of memory modules can be placed in the first bank of each channel, and a pair of modules of different capacity in the second bank. Modules rated at different speeds can be run in dual-channel mode, although the motherboard will run all memory modules at the speed of the slowest module. However, some motherboards have compatibility issues with certain brands or models of memory when trying to use them in dual channel mode. For this reason, it is generally recommended to use identical pairs of memory modules, which is why most memory manufacturers now sell "kits" for them. of matched pair DIMMs. Several motherboard manufacturers only support configurations where a "matched pair" of modules. A matching pair must match on:
- Capacity (for example, 1024 MB). Certain sets of Intel chips support chips of different capacities in what they call Flex Mode: the capacity that can be matched runs on two channels, while the rest runs on a single channel.
- Speed (e.g. PC5300). If the speed is not the same, the lowest speed of the two modules will be used. In addition, the highest level of the two modules will be used.
- Misma latencia CAS (CL) or strobe light of column direction.
- Number of chips and sides (e.g. two sides with four chips on each side).
- Matching size of rows and columns.
Dual channel architecture is a technology implemented on motherboards by the motherboard manufacturer and does not apply to memory modules. Theoretically, any pair of memory modules combined can be used in single or dual channel operation, as long as the motherboard supports this architecture.
Performance
Theoretically, dual-channel configurations double the memory bandwidth compared to single-channel configurations. This is not to be confused with Double Data Rate (DDR) memory, which doubles the usage of the DRAM bus by transferring data on both the rising and falling edges of the memory bus clock signals.
A benchmark test by TweakTown, using SiSoftware Sandra, measured around a 70% increase in performance for a four-channel setup, compared to a two-channel setup. Other tests by TweakTown on the same theme showed no significant differences in performance, leading to the conclusion that not all reference software is up to the task of exploiting the greater parallelism offered by multi-channel memory configurations.
In a group vs. not in a group
Dual channel was originally envisioned as a way to maximize memory performance by combining two 64-bit buses into a single 128-bit bus. This is retrospectively called the "bundled" mode. However, due to lackluster performance gains in consumer applications, most modern dual-channel implementations use the "unmodified" by default, it maintains two 64-bit memory buses but allows independent access to each channel, in support of multithreading with multicore processors.
The difference between "bundled" and "not grouped" it could also be thought of as an analogy to the way RAID 0 works, compared to JBOD. With RAID 0 (which is analogous to 'striped' mode), it is up to the additional logic layer to provide better use (ideally uniform) of all available hardware units (storage devices or memory modules) and higher overall performance. On the other hand, with JBOD (which is analogous to "non-pooled" mode) we rely on statistical usage patterns to ensure higher overall performance through uniform use of all available hardware drives.
Triple channel architecture
Operation
DDR3 triple channel architecture is used in the Intel Core i7-900 series (Intel Core i7-800 series only supports up to two channels). The LGA 1366 platform (eg Intel X58) supports triple channel DDR3, typically 1333 and 1600 MHz, but can run at higher clock speeds on certain motherboards. AMD Socket AM3 processors do not use the DDR3 triple channel architecture, but instead use dual channel DDR3 memory. The same applies to the Intel Core i3, Core i5 and Core i7-800 series, which are used on LGA 1156 platforms (for example, Intel P55). According to Intel, a Core i7 with DDR3 running at 1066 MHz will deliver maximum data transfer speeds of 25.6 GB/s when operating in tri-channel interleaved mode. This, Intel claims, leads to faster system performance, as well as higher performance per watt.
When operating in three-channel mode, memory latency is reduced due to interleaving, which means that each module is accessed sequentially for smaller data bits instead of completely filling a module before to access the next. Data is distributed among the modules in an alternating pattern, potentially tripling the available memory bandwidth for the same amount of data, rather than storing it all on one module.
The architecture can only be used when all three memory modules, or a multiple of three, are identical in capacity and speed, and are placed in three-channel slots. When two memory modules are installed, the architecture will work in dual channel architecture mode.
Supported processors
Four-channel architecture
Operation
Quad-channel memory debuted on the Intel Nehalem-EX LGA 1567 Xeon CPU platform, aka Beckton in 2010, and was introduced to the high-end product line on the Intel X79 LGA 2011 platform with Sandy Bridge -E in late 2011. DDR4 replaced DDR3 on the Intel X99 LGA 2011 platform, also known as Haswell-E, and is also used on AMD's Threadripper platform. The DDR3 quad-channel architecture is used on the AMD platform G34 and on the aforementioned Intel CPUs before Haswell. AMD processors for the C32 platform and Intel processors for the LGA 1155 platform (eg Intel Z68) use dual-channel DDR3 memory instead.
The architecture can be used only when all four memory modules (or a multiple of four) are identical in capacity and speed, and are placed in four-channel slots. When two memory modules are installed, the architecture will work in a dual channel mode; When three memory modules are installed, the architecture will operate in tri-channel mode.
Supported processors
Six-channel architecture
Compatible with Qualcomm Centriq server processors, and Intel Xeon Scalable platform processors.
Eight-channel architecture
Compatible with Cavium ThunderX2 server processors, AMD server processors from their Epyc platform, and the Threadripper PRO line of professional-class workstation processors from the AMD Ryzen PRO family of products.