AGP is the abbreviation of accelerated graphics port. It is a special expansion slot for display card. It is developed on the basis of PCI graphics interface. AGP specification is issued by Intel to solve the problem of poor computer processing (mainly display) 3D graphics. AGP is not a bus, but an interface mode. As 3D games become more and more complex, a large number of 3D effects and textures are used, which makes the PCI bus with the original transmission rate of 133mb / sec more and more overwhelmed. For this reason, Intel launched the AGP interface with high bandwidth. This is a graphics interface completely different from the PCI bus. It is completely independent of the PCI bus and directly connects the graphics card with the motherboard control chip, so that the process of 3D graphics data crossing the PCI bus is omitted, so as to solve the system bottleneck caused by low bandwidth PCI interface. It can be said that it is inevitable for AGP to replace PCI as a new graphics port.

AGP slot standard

AGP standard:AGP standards are divided into agp1.0 (AGP 1x and AGP 2x), agp2.0 (AGP 4x) and agp3.0 (AGP 8x).

At present, the commonly used AGP interfaces are agp4x, AGP pro, AGP general and agp8x interfaces. It should be noted that since the rated voltage of agp3.0 graphics card is 0.8-1.5v, the agp8x graphics card cannot be inserted into the agp1.0 slot. This means that the agp8x specification is incompatible with the old agp1x / 2x mode. For agp4x system, agp8x graphics card still works on it, but it will only work in agp4x mode, which can not give full play to the advantages of agp8x.

Explanation of AGP concept introduction to four AGP slot standards

AGP 1.0(AGP1X、AGP2X)

In July 1996, AGP 1.0 graphics standard came out, which is divided into 1x and 2x modes, and the data transmission bandwidth has reached 266mb / s and 533mb / s respectively. This graphic interface specification is formed by expanding and strengthening on the basis of 66MHz pci2.1 specification. Its working frequency is 66MHz and its working voltage is 3.3V. It basically meets the needs of data exchange between display equipment and system in a period of time. The AGP bandwidth in this specification is very small and has been eliminated now. It can only be seen on the old motherboard in previous years.

AGP2.0(AGP4X)

With the rapid development of display chip, the data that can be processed by graphics card per unit time increases exponentially. AGP 1.0 graphics standard is more and more difficult to meet the progress of technology, so AGP 2.0 came into being. In May 1998, AGP 2.0 specification was officially released. The working frequency is still 66MHz, but the working voltage is reduced to 1.5V, and 4x mode is added. In this way, its data transmission bandwidth reaches 1066mb / sec, and the data transmission capacity is greatly enhanced.

AGP Pro

AGP Pro interface and AGP 2.0 are launched at the same time. This is a graphic interface standard developed to meet the reality of increasing power consumption of display equipment. The main feature of the graphic interface using this technology is that it is slightly longer than AGP 4x, and its extension can accommodate more power pins, so that this interface can drive higher power consumption (25-110w) Or AGP graphics card with more powerful processing power. This standard is actually designed for high-end graphics workstations and is fully compatible with AGP 4x specification, so that AGP 4x graphics cards can also be inserted into this slot for normal use. The AGP Pro extends on both sides of the original AGP slot to provide additional power. It is used to enhance, not replace, the functionality of existing AGP slots. AGP Pro can be subdivided into AGP pro110 and AGP pro50 according to the different energy provided. AGP Pro slots can also be seen on some high-end desktop motherboards, such as many motherboards of ASUS.

AGP3.0(AGP8X)

In August 2000, Intel introduced agp3.0 specification, and the working voltage dropped to 0.8V. In order to prevent users from using non-0.8v graphics cards in AGP 0.8V slots, Intel specially added electronic IDs for AGP 3.0 slots and motherboards, which can support 1.5V and 0.8V signal voltages. 8x mode is added, so that its data transmission bandwidth reaches 2133mb / sec, and the data transmission capacity is doubled compared with AGP 4x, which can better meet the bandwidth requirements of current display devices.

Different AGP interfaces have different transmission modes. The working frequency of 1x mode AGP is twice that of PCI bus – 66MHz, and the transmission bandwidth can theoretically reach 266mb / s. The working frequency of AGP 2x is also 66MHz, but it uses the working mode triggered by positive and negative edges (rising and falling edges of a clock cycle). In this triggering mode, data is transmitted once on the rising and falling edges of a clock cycle, so that a working cycle is triggered twice successively, so that the transmission bandwidth is doubled, The operating frequency of this trigger signal is 133MHz, so the transmission bandwidth of AGP 2x reaches 266mb / S & times; 2 (trigger times) = 533mb / s height. AGP 4x still uses this signal trigger mode, but uses two trigger signals to trigger twice on the falling edge of each clock cycle, so as to trigger four times in a clock cycle. In theory, it can reach 266mb / S & times; 2 (single signal trigger times) & times; 2 (number of signals) = 1066mb / s bandwidth. In the AGP 8x specification, this trigger mode is still used, except that the working frequency of the trigger signal becomes 266MHz, the two signal trigger points also become the rising edge of each clock cycle, and the number of single signal triggers is 4 times. In this way, the data it can transmit in a clock cycle is changed from 4 times of agp4x to 8 times, and the theoretical transmission bandwidth will reach 266mb / S & times; 4 (single signal trigger times) × 2 (number of signals) = 2133mb / s.

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