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| AGP (Pro) Bus Definition |
 Accelerated Graphics Port A high-speed 32-bit port from Intel for attaching a display adapter to a PC. It provides a direct connection between the card and memory, and only one AGP slot is on the motherboard. AGP was introduced as a higher-speed alternative to PCI display adapters, and it freed a PCI slot for another peripheral device. The brown AGP slot is slightly shorter than the white PCI slot and is located about an inch farther back. AGP is superseded by PCI Express.
AGP 1x, 2x, 4x and 8x:
- AGP 1x, using a 32-bit channel operating at 66 MHz resulting in a maximum data rate of 266 megabytes per second (MB/s), doubled from the 133 MB/s transfer rate of PCI bus 33 MHz / 32-bit; 3.3 V signaling.
- AGP 2x, using a 32-bit channel operating at 66 MHz double pumped to an effective 133 MHz resulting in a maximum data rate of 533 MB/s; signaling voltages the same as AGP 1x.
- AGP 4x, using a 32-bit channel operating at 66 MHz quad pumped to an effective 266 MHz resulting in a maximum data rate of 1066 MB/s (1 GB/s); 1.5 V signaling.
- AGP 8x, using a 32-bit channel operating at 66 MHz, strobing eight times per clock, delivering an effective 533 MHz resulting in a maximum data rate of 2133 MB/s (2 GB/s); 0.8 V signaling.
Bus Comparison
Chart
| Bus Type |
MB/sec |
| ISA |
16 MBps |
| EISA |
32 MBps |
| VL-bus |
100 MBps |
| VL-bus |
132 MBps |
| PCI |
132 MBps |
| PCI |
264 MBps |
| PCI-X 66 |
512 MBps |
| PCI-X 133 |
1 GBps |
| AGP x1 |
264 MB/s |
| AGP x2 |
528 MB/s |
| AGP x4 |
1056 MB/s |
| AGP x8 |
2112 MB/s |
| PCI Express x1 |
500 MB/s |
| PCI Express x2 |
1000 MB/s |
| PCI Express x4 |
2000 MB/s |
| PCI Express x8 |
4000 MB/s |
| PCI Express x12 |
6000 MB/s |
| PCI Express x16 |
8000 MB/s |
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There are two versions of the AGP physical interface, for 3.3 V
and 1.5 V cards respectively.
1.5V AGP Slot |
The 1.5 V version has a key further away from the external connector,
while the 3.3 V version is the opposite. But some poorly designed
older 3.3V cards incorrectly have the 1.5V key, which may result
in burnt mainboard if installed in a AGP 4X/8X slot.
AGP cards are backwards and forwards compatible within limits. 1.5 V cards will not go into 3.3 V slots and vice versa, though "Universal" slots exist which accept either type of card. AGP Pro cards (rarely used) will not fit into standard slots, but standard AGP cards will work in a Pro slot.
AGP Pro
AGP Pro is a extention to the standard AGP connector and slot on both sides to provide additional power to an AGP card. It comes in two flavors, AGP Pro110 provides for 50-110W of power and requires two adjacent PCI slots for cooling. AGP Pro50 provides for 20-50W of power and requires a single adjacent PCI slot for cooling. An AGP Pro video card will not work in an AGP slot. An AGP video card will work in an AGP Pro slot, however the card must have a registration tab.
AGP Slots and Cards come in 3.3V
and 1.5V options. Below is an illustration of what 32-bit
PCI 5V, 3.3V and univesal goldfingers and slots looks
like.
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| AGP
Slot Voltage Visual Comparison |
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| AGP
Golfinger Voltage Visual Comparison |
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AGP Pro Slots and Cards come in 3.3V
and 1.5V options. Below is an illustration of what 64-bit
PCI 5V, 3.3V and univesal goldfingers and slots looks
like.
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| AGP
Pro Slot Voltage Visual Comparison |
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| AGP
Pro Golfinger Voltage Visual Comparison |
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