In this section, we will discuss a variety of RAM that differs in ways of implementing system memory on motherboard.
Single, Dual and Triple Channel Memory
Memory controllers provide memory access in chunks of the size same as the system bus’s data width, leading to communication over a single channel. A 64-bit system data bus is provided in most of the modern processors. This implies that exactly 64 bits of information can be transferred by a standard memory controller at a time. In an environment where the CPU and the memory can operate faster than the conduit between them, communication over a single channel creates a bottleneck. This bottleneck can be eased a little by adding channels parallel between the CPU and the RAM.
To ease this bottleneck between the CPU and RAM, memory controllers that support dual- and triple-channel memory implementations are available. The memory controller in a dual-channel memory will coordinate two memory banks, which in turn work as a synchronised set during their communication with the CPU. This arrangement doubles the specified system bus width for the memory. Similarly, triple-channel memory requires coordination of three memory modules simultaneously.
Unlike the dual-channel architectures, triple-channel memory allows a kind of interleaving to reduce the amount of information shared by each module. As triple-channel memory accesses more information per unit of time, triple-channel architectures have greater performance than dual-channel architectures with dual-channel memory.
The banks and modules are set in a 1:1 ratio. This is because of the modern-day processors with 64-bit external data buses and only one memory stick. Thus, to implement dual- and triple- channel memory in today’s most popular computer systems, memory modules need to be installed as pairs or triads at a time. Remember that motherboard implements the dual- and triple-channel memory — not the memory. Contrastingly, single-channel memory is a classic memory model requiring a complete bank to be satisfied for initial installation or addition of memory. For example, a single bank supplies only one half of the width of effective bus created by the dual-channel support. As the name suggests, dual-channel support pairs two memory banks at a time.
To enhance the system’s overall performance, the memory subsystems are applied with different tricks. This demands extra care while installing dissimilar memory modules. In a worst-case scenario, the PC will stop functioning if dissimilar modules with different capacities, number of sides, or speeds are placed together in slots of the same channel. The modules should get easily paired in cases where all these parameters are identical. There is still a possibility that issues may occur if the placed modules are from two different manufacturers, even if the other parameters remain unchanged. In such cases, you may take help from technical support or documentation from your motherboard’s manufacturer. The motherboard technology is responsible for dual-channel support. Unlike the motherboard memory slots, memory modules do not have any colour coding.
Single-Sided vs Double-Sided Memory
Single-sided memory is a RAM module that is mounted on one side of the memory stick. It fills a single bank. This means that the memory controller accesses all memory chips on the module at the same time. Single-sided RAM consists of only one group of chips that the controller sees all at the same time. It is much faster than double-sided RAM. DDR RAM comes in single-sided version of RAM.
Double-sided memory comprises two groups of chips. The memory controller sees each of the two groups separately and can read or write one at a time by switching back and forth between group of chips.
Buffered vs Unbuffered Memory
Buffered memory, also called registered memory, is a memory having a buffer (temporary storage) between DRAM and memory controller. It generally reduces the load on memory controller and makes it stable. Buffered memory has a few numbers of units that are sold and has additional circuitry required. For this reason, it is more expensive than unbuffered memory. it is used for workstations and servers. Mostly, the ECC memory is buffered.
Unbuffered memory, also called unregistered memory, is a memory having no buffer between DRAM and memory controller. This leads to a direct access to memory controller and is more efficient than buffered memory. It is the choice for home systems as it is cheaper and faster.