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Intel's New Advanced Graphics Port
Intel has been promising their Advanced Graphic Port for a year. Now with the release of the new Pentium-II LX chipset, it is finally here. AGP is a new type of bus design. On a computer's motherboard, there are two types of expansion slots, ISA and PCI. ISA is an older form of expansion slot, and most expansion cards today use the newer PCI bus. With the Advanced Graphics Port, Intel has designed an expansion slot just for video cards.
Until AGP, most video cards used the PCI bus, with a few older video cards using the ISA bus. The PCI bus ran at 33mhz, half of the system speed (66mhz). Running at 33mhz, the PCI bus could have a maximum transfer rate of 132mb/s. The Advanced Graphic Port runs at 66mhz, giving an increased transfer rate of 266mb/s (referred to as x1). In addition to x1 transfer speeds, AGP uses new technology with allows it to double its bandwidth by transferring on the rising and falling timings of the 66mhz clock to get 532mb/s (referred to as x2). A further benefit of AGP over the PCI bus is that it is a dedicated bus, unlike PCI with can have other devices taking up its bandwidth. The increased transfer speeds to the main CPU and memory allow for increased speed in graphical operations (mostly 3D operations).
The other main feature of the Advanced Graphics Port is "Direct Memory Execute" (or DIME). It allows for video card to use some of the main memory for texture memory with 3D graphics. Usually video cards have four megabytes of RAM, with a few having eight. DIME allows for 12, 16, or even more memory to be used by allocating some of the main system memory. The increased amount of memory increases the graphical speed during high-resolution 3D scenes. Before AGP, high-resolution 3D scenes were nearly impossible to use with a decent frame rate. There were a few PCI cards that offered up to 32mb of RAM onboard, but they were very expensive.
The easiest way to understand DIME, is to think of it as giving the video card direct access to the main system components. The following image is a good example of this. (Thanks to Diamond Multimedia)
Until AGP, most video cards used the PCI bus, with a few older video cards using the ISA bus. The PCI bus ran at 33mhz, half of the system speed (66mhz). Running at 33mhz, the PCI bus could have a maximum transfer rate of 132mb/s. The Advanced Graphic Port runs at 66mhz, giving an increased transfer rate of 266mb/s (referred to as x1). In addition to x1 transfer speeds, AGP uses new technology with allows it to double its bandwidth by transferring on the rising and falling timings of the 66mhz clock to get 532mb/s (referred to as x2). A further benefit of AGP over the PCI bus is that it is a dedicated bus, unlike PCI with can have other devices taking up its bandwidth. The increased transfer speeds to the main CPU and memory allow for increased speed in graphical operations (mostly 3D operations).
The other main feature of the Advanced Graphics Port is "Direct Memory Execute" (or DIME). It allows for video card to use some of the main memory for texture memory with 3D graphics. Usually video cards have four megabytes of RAM, with a few having eight. DIME allows for 12, 16, or even more memory to be used by allocating some of the main system memory. The increased amount of memory increases the graphical speed during high-resolution 3D scenes. Before AGP, high-resolution 3D scenes were nearly impossible to use with a decent frame rate. There were a few PCI cards that offered up to 32mb of RAM onboard, but they were very expensive.
The easiest way to understand DIME, is to think of it as giving the video card direct access to the main system components. The following image is a good example of this. (Thanks to Diamond Multimedia)
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