What is the memory frequency?

　　memory frequency is the same as CPU frequency, is used to represent the speed of memory, it represents the maximum operating frequency that memory can achieve. The memory frequency is measured in MHz (MHz). the higher the memory frequency is to a certain extent, the faster the memory can reach. The frequency of memory determines how often the memory can work correctly. Currently the more mainstream memory frequency rooms are 333MHz and 400MHz of DDR memory, as well as 533MHz and 667MHz of DDR2 memory.

As you know, the clock speed of computer system is measured by frequency. The crystal oscillator controls the clock speed and adds voltage to the quartz wafer, which vibrates in the form of a sine wave, which can be recorded by the deformation and size of the wafer. The vibrations of the crystals are expressed in the form of sinusoidal and varying currents, the current of which is the clock signal. And the memory itself does not have a crystal oscillator, so the memory work clock signal by the motherboard chipset of the North Bridge or directly by the motherboard of the clock generator provided, that is, memory can not determine its own working frequency, its actual operating frequency is determined by the motherboard.

The frequency of DDR memory and DDR2 memory can be expressed in two ways, working frequency and equivalent frequency, which is the actual operating frequency of the memory particles, but the equivalent frequency of the transmitted data is twice times that of the operating frequency because the DDR memory can transmit data along the pulse's ascent and descent. and DDR2 memory each clock can read/write data at four times times the rate of work, so the equivalent frequency of the transmitted data is four times times that of the working frequency. For example, the working frequencies of the DDR 200/266/333/400 are 100/133/166/200mhz, and the equivalent frequencies are 200/266/333/400MHZ;DDR2 400/533/667/800 respectively 100/133/ 166/200mhz, and the equivalent frequencies are 400/533/667/800mhz respectively.

The memory asynchronous working mode contains a variety of meanings, which can be called the memory asynchronous working mode when the general memory working frequency is inconsistent with the CPU's FSB. First, the earliest memory asynchronous mode of operation appears in the early motherboard chipset, allowing the memory to work in a mode that is higher than the CPU FSB 33MHz or low 33MHz (note that the simple difference is 33MHz), which can improve system memory performance or keep old memory from remaining exhausted. Second, in normal working mode (CPU not overclocking), many motherboard chipsets also support the memory asynchronous mode of operation, such as the Intel 910GL chipset, only support 533MHz FSB, 133MHz of CPU FSB, but can match the working frequency of the 133MHz DDR 266 , 166MHz DDR 333 and working 200MHz DDR 400 work correctly (note that at this point its CPU FSB 133MHz and DDR 400 working frequency 200MHz has been 66MHz), but with different memory there is a difference in performance. Again, in the case of CPU overclocking, in order not to allow the memory to drag the CPU overclocking ability of the hind legs, at this time can reduce the operating frequency of memory to facilitate overclocking, such as AMD Socket 939 Interface Opteron 144 very easy to overclocking, many products FSB can easily exceed 300MHz, This is clearly not possible in the case of memory synchronization in which the equivalent frequency of the memory will be as high as DDR 600, and in order to go beyond 300MHz FSB, we can set the memory to DDR 333 or DDR 266 in the motherboard BIOS before overclocking, after 300MHz FSB, The former also only DDR 500 (some of the best memory can be achieved), and the latter is only DDR 400 (completely normal standard frequency), thus, the correct set of memory asynchronous mode to help overclocking success.

The current motherboard chipset supports almost all memory asynchrony, and Intel is supported from the 810 series to the newer 875 series, while Granville provides this functionality from the 693 chipset.