Notebook dual-Channel memory introduction

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Dual-channel memory technology is actually a memory control and management technology that relies on the memory controller of the chipset to be able to increase the bandwidth of two equal-specification memory by one times in theory. 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 the Axx aspect is the NVIDIANforce2 series.

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Dual-channel memory technology is a low-cost, High-performance solution that solves the problem of CPU bus bandwidth and memory bandwidth. Now that the CPU's FSB (front bus frequency) is getting higher, Intel PENTIUM4 has a much higher demand for memory bandwidth than AXXATHLONXP. The Intel PENTIUM4 processor and North Bridge chip data transmission using the QDR (quaddatarate, four data transmission) technology, its FSB is FSB 4 times times. Intel PENTIUM4 's FSB is 400, 533, 800MHz, bus bandwidth is 3.2gb/sec,4.2gb/sec and 6.4gb/sec respectively, and ddr266/ddr333/ddr400 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 DDR266, DDR333, DDR400 can provide the memory bandwidth is 4.2gb/sec,5.4gb/sec and 6.4gb/sec, which can be seen here, Dual-channel DDR400 memory is just enough to meet the bandwidth requirements of the 800MHZFSBPENTIUM4 processor. And for the AXXATHLONXP platform, its processor and North Bridge chip data transmission technology using DDR (DOUBLEDATARATE, double data transmission) technology, FSB is FSB twice times, its demand for memory bandwidth is much lower than the Intel PENTIUM4 platform, its FSB 266, 333, 400MHz, bus bandwidth is 2.1gb/sec,2.7gb/sec and 3.2gb/sec, the use of single channel DDR266, DDR333, DDR400 can meet its bandwidth requirements, Therefore, the use of dual-channel DDR memory technology on the AXXK7 platform is less effective, and performance improvement is not as obvious as the Intel platform, the most obvious performance impact is the integration of the integrated display chip motherboard.

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 (128bit Parallel Memory interface) is no easy feat for many chipset vendors. Ddrsdram 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 Ddrsdram memory has its own limitations, it is a low latency characteristics, the use of parallel transmission mode, and the most important point: when the Ddrsdram working 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 platforms with Intel's 865P, 865G, 865GV, 865PE, 875P, and subsequent 915, 925 series; Via Pt880,ati's RADEON9100IGP series, Sis Siis655,sis655fx and SIS655TX; The Axx platform has via Kt880,nvidia's NFORCE2ULTRA400,NFORCE2IGP,NFORCE2SPP and its subsequent chips.

Axx 64-bit CPU, because of the integration of memory controller, so whether to support memory dual-channel look at the CPU. Currently Axx Desktop CPU, only 939 interface support memory dual channel, 754 interface does not support memory dual channel. In addition to the Axx 64-bit CPU, whether other computers can support memory dual-channel depends primarily on the motherboard chipset, supports dual-channel chipsets with descriptions, and can view motherboard chipset data. In addition, some chipsets in theory support the different capacity of the memory bar to achieve dual channel, but actually it is recommended to use a consistent two of the parameters of the memory bar.

Memory dual-channel generally requires the memory slot on the motherboard to use the color, in addition to some motherboards also need to do in the BIOS settings, General motherboard specifications will be described. When the system has implemented dual-channel, some motherboards will be prompted at post, you can take a closer look. Since the self-test is faster, it may not be visible. So you can use some software to view, many software can check, such as cpu-z, relatively small. In the term "memory" there is a "channels" project, if the word "Dual" is shown here, it means that two channels have been implemented. Two 256M of RAM makes the dual channel effect better than a 512M memory because one memory cannot form a dual channel.