Tell everyone what is dual channel? _ Hardware Maintenance

First build the dual-pass memory must be a dual-1G memory is not allowed to open two channels
What is a dual channel?
Dual-channel memory technology is actually a memory control and management technology, which relies on the memory controller of the chipset to be able to theoretically enable two of the same size of memory to provide the bandwidth of one-fold increase. It is not a new technology that has long been applied to servers and workstation systems, but only to the Desktop board technology front desk to address the increasingly embarrassing memory bandwidth bottlenecks in desktops. A few years ago, Intel Corporation had launched a I820 chipset that supported dual-channel memory transfer technology. It and RDRAM memory constitute a pair of gold partner, play out of the outstanding performance so that it has become the market's biggest bright spot, but the production cost is too high the flaw has caused the applause not to draw the case, finally by the market eliminated. Since Intel has abandoned support for RDRAM, the current dual-channel memory technology for mainstream chipsets refers to dual-channel DDR memory technology, the main dual-channel memory platform Intel is the Intel 865/875 series, and AMD is the Nvidia Nforce2 series.
Dual-channel memory technology is a low-cost, high-performance solution to the problem of CPU bus bandwidth and memory bandwidth. Now that the CPU's FSB (front bus frequency) is getting higher, Intel Pentium 4 has a much higher demand for memory bandwidth than AMD Athlon XP. The Intel Pentium 4 processor and North Bridge chip data transfer using QDR (Quad data Rate, four data transmission) technology, the FSB is 4 times times the FSB. The FSB for intel® Pentium 4 is 400/533/800mhz, bus bandwidth is 3.2gb/sec,4.2gb/sec and 6.4gb/sec respectively, and DDR 266/DDR 333/DDR 400 can provide the memory bandwidth is 2.1gb/ Sec,2.7gb/sec and 3.2gb/sec. In single channel memory mode, the DDR memory does not provide the data bandwidth required by the CPU and thus becomes a performance bottleneck for the system. In dual-channel memory mode, dual-channel DDR 266/DDR 333/DDR 400 can provide the memory bandwidth of 4.2GB/SEC,5.4GB/SEC and 6.4gb/sec, which can be seen here, dual-channel DDR 400 memory can meet the 800MHz FSB Pentium 4 Processor bandwidth requirements. For AMD Athlon XP platform, its processor and North Bridge chip data transmission technology using DDR (double data Rate, double data transmission) technology, FSB is the FSB twice times, its demand for memory bandwidth is much lower than the Intel Pentium 4 platform, Its FSB is 266/333/400mhz, bus bandwidth is 2.1gb/sec,2.7gb/sec and 3.2gb/sec respectively, use single channel DDR 266/DDR 333/DDR 400 can meet its bandwidth demand, so in AMD The use of dual-channel DDR memory technology on the K7 platform is less effective and performance improvement is not as obvious as the Intel platform, and the most significant performance impact is the integration of integrated motherboards.
The nforce chipset introduced by NVIDIA is the first chipset to extend the DDR memory interface to 128-bit, and Intel also uses this dual-channel DDR memory technology on its E7500 server board chipset, and SIS and via are responding, Actively develop this technology that will multiply the DDR memory bandwidth. However, for a variety of reasons, the transfer of this dual-channel DDR (128 bit parallel memory interface) is no easy feat for many chipset vendors. DDR SDRAM memory is completely different from rdram memory, which has a high latency feature and is serial transmission, which determines the difficulty and cost of designing a dual-channel RDRAM memory chipset. But DDR SDRAM memory has its own limitations, it is a low latency characteristics, the use of parallel transmission mode, but also the most important point: when the DDR SDRAM operating frequency is higher than 400MHz, its signal waveform often appear distortion problem, These are all designed to make a chipset that supports dual-channel DDR memory systems a little more difficult, and the manufacturing cost of the chipset increases correspondingly, and these factors constrain the development of this memory-control technology.
The common single channel memory system has a 64-bit memory controller, while the dual-channel memory system has 2 64-bit memory controller, in dual-channel mode with 128bit of memory bit width, so that the memory bandwidth in theory to increase by one times. Although the bandwidth provided by a dual 64-bit memory system is equivalent to the bandwidth provided by a 128-bit memory system, the results are different. The dual-channel system contains two independent, complementary intelligent memory controllers, and in theory, two memory controllers can operate at the same time with 0 delays between them. For example, two memory controllers, one for a and another for B. When controller B is ready for the next access memory, controller A is reading/writing primary memory, and vice versa. This complementary "nature" of two memory controllers can reduce the wait time by up to 50%. The two memory directors for dual-channel DDR are functionally identical, and the timing parameters of the two controllers can be programmed individually. This flexibility allows the user to use two different structure, capacity, speed DIMM memory, when the dual-channel DDR simply adjusts to the lowest memory standard to achieve 128bit bandwidth, allowing the different density/latency characteristics of the DIMM memory can be reliably common operation.
Desktop chipsets that support dual-channel DDR memory technology, Intel 865p/865g/865gv/865pe/875p and the following 915/925 series; via Pt880,ati's radeon 9100  IGP series, SIS SIIS 655,SIS 655FX and SIS 655TX;AMD platforms have via Kt880,nvidia nforce2 ultra  400,NFORCE2 IGP,NFORCE2 SPP and its subsequent chips.