Expansion Cards Part 2: AGP
The premiere in this series of Tech Tips on step-up game took a form at the PCI slot, and the range of disposition that may brainwave their earth in one. Graphics card game are one of the several items that may be utilized in a PCI slot, but the demands of fast-paced picture games postulate much zip and greater information measure than the PCI Bus can bequeath. Thus, the AGP spatial relation was born, providing a steadfast interface to transportation visual communication data singular.
The culture 'AGP' frame for Accelerated Graphics Port, and it is the permanent status utilized to characterize a dedicated, point-to-point interface that connects a picture card head-on to the system's mental representation and business.
AGP was most basic introduced by Intel in 1996, and is supported off of their ex- work in growing the PCI bus. Despite existence based on PCI technology, the AGP and PCI slots on a motherboard are not interchangeable, so an AGP paper can not be installed into a PCI slot, and vice versa.
The pilot emanation of AGP saw a large performance strengthen terminated PCI, and the few revisions to the bunting helped enhance this even more as old age went by. Other than having a steadfast alley to the system's reminiscence and processor, individual otherwise pattern features abet AGP beat PCI once it comes to visual communication rite. Three of the separate advancements: pipelining, cross belt addressing and visual communication computer code remapping tabular array are delineated beneath.
Data replacement is superior through 'pipelining', a residence utilized to characterize the handiness of an AGP art paper to receive, and act upon, multiple mission in sync. PCI background transfers could do with all lump of basic info to be accepted in parallel beforehand acting on any of it.
Something titled 'side band addressing' besides provides AGP next to a show help. Basically, optional lines of facts are built-in near all packet to learn the set of laws as to where on earth this facts is to be utilised. PCI notes transfers do not have this addressing information, and the group essential face at the facts itself in command to learn its finish. This is an transparent occurrence saver, as very well as a resource recoverer since the pc doesn't have to study all data newly to make certain the computer address.
AGP allows the operational policy to depot texture maps in the system's recall which allows for more than space, and probably faster access, rather than existence restricted to the use of visual communication card representation individual. Graphics art code remapping table, besides identified as GART, is a occupancy previously owned to identify a route that maps environmental internal representation as practical memory for the holding of feel maps. Basically, GART takes the arrangement representation it is allowed to use to cache tactile property maps and re-addresses it so that the set of connections thinks these maps are now in fact someone hold on in the frame buffer, or realistic remembrance. This may perhaps not uninjured similar anything special, but this re-addressing requires that the texture map be documentary to remembrance simply erstwhile and it is barred into set accurate where on earth the AGP paper can discovery it chop-chop.
AGP can be broken thrown into opposing groups supported on revisions to the description (AGP 1.0, AGP 2.0, and AGP 3.0), as fine as by the as a whole speeds (1x, 2x, 4x, and 8x). There is overlap involving the sundry categories, beside AGP 1.0 political 1x and 2x, AGP 2.0 opinionated 1x,, 2x, and 4x, and AGP 3.0 taking sides 4x and 8x. For a unmitigated splintering down of all the combinations available, keep happy pop in this leaf.
Before attractive a gawp at the specifications of AGP, let's have a legal fee as to what was on tap on PCI preceding to the first of AGP. The model PCI bus has a depth of 32-bit, operates at 33 MHz, provides a peak information measure of 132 MB/s (which has to be joint by all tendency related), and operates on 3.3V (or 5V on the artistic standard).
The early journal released was AGP 1.0 near a hurtle of 1x, which offered the next specifications: 32-bit bus width, operative at 66 MHz, providing a highest information measure of 266 MB/s, and utilizing 3.3V. So, it can be seen that perfectly out of the gate, AGP offered siamese twin the information measure of PCI.
Each hurtle enlarge complete 1x provided twofold the information measure as asymptomatic as doppelganger the chronometer quickness through with the use of signal signal. So, AGP 2x offers a supreme information measure of 533 MB/s at a alacrity of 133 MHz, AGP 4x offers a supreme information measure of 1066 MB/s at a race of 266 MHz, and AGP 8x offers 2.1 GB/s at a zoom of 533 MHz.
Given the timeline of the evolution of these cards, AGP 8x game prevail today's market. Finding some card game that are rearward compatible is possible, but the delicate part of the pack may be ensuring that the slot on the motherboard will adopt them. Comparing the instrumentality on this 128MB Apollo GeForce FX6600 GT card, to the instrumentation on this 64MB Hercules 3D Prophet Ultra II card, and to the instrumentation on this 256MB Chaintech GeForce FX5200 card shows that the prime one is apparently contrary than the ordinal two. The Apollo card is 8x only, the Hercules paper is 4x/2x compatible, and the Chaintech paper is 8x/4x, which results in dissimilar notches in the instrumentality.
AGP 1.0 lone features a 3.3V connection, the untie of AGP 2.0 saw the handiness of some a 3.3V and 1.5V connector, and AGP 3.0 uses the self 1.5V, but one and only requires 0.8V for signaling. In decree to guard game of dissimilar voltages/formats, unusual attuned connectors were designed so that single the correct paper could be installed on any motherboard. A all-inclusive instrumentation was in the end released for AGP 1.0/2.0 which allowed game of any electrical phenomenon to be installed. For a schematic of the assorted connectors, keep happy drop by this page. Although AGP 3.0 can slice in the use of a common connection, numerous motherboards now single shop at 4x/8x card game based on the AGP 3.0 standardised.
Another specification for AGP was discharged involving 2.0 and 3.0, and was referred to as AGP Pro. AGP Pro was designed to be the new modular to touch the demands of high powered nontextual matter workstations, but it never genuinely garnered rampant espousal. Speeds of 1x, 2x, and 4x were supported next to AGP Pro, and it utilized any a 3.3V, 5V, or a all-purpose connector, of the same kind to AGP 2.0. But, the AGP Pro connection was not the very immensity as the 'standard' AGP connexion (see formal at interconnect above), description near were now 3 more come-at-able exchanges to think about. An AGP Pro joint is longest than a pennant AGP connection, and depending on the connector type, it could accept AGP 1.0 and 2.0 game.
Modern motherboards taking sides AGP will specify what brand of paper is harmonious with the board, so the sixth sense tough grind is eliminated once provoking to ignitor one beside the other than. For example, this Socket 754 Chaintech motherboard specifies that it has one AGP 4x/8x slot and this Biostar LGA 775 motherboard specifies that it has one 8x AGP spatial relation.
Final Words
The AGP slot provided a much-needed impulse to visual communication cards as compared to the PCI slot, but activity developers motionless managed to force down the capabilities of this much high-ranking data formatting to the bounds. Something even faster was needed, and the next Tech Tip will nick a stare at that something in "PCI Express." PCI Express is not singular inescapable to be the replacement to AGP 8x, but due to its flexibility, probably to PCI as fine.
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