New features

Still, some of the new features seem quite interesting for 3D games. One of them is the new AGP 8x mode, which increases the effective bandwith up to 2.1 GB/s. This feature, however, has to be eyed with suspicion, recent tests show that modern games don't even benefit from AGP 4x.

Another significant change is the the signal-reduction from 1.5V down to 0.8V, which is a decrease of 47 %. One might remember the trouble, the reduction from 3.3V (AGP 1.0) to 1.5V (AGP 2.0) caused on some motherboards with certain video cards. An AGP 2.0 compatible motherboard doesn't have to care about 3.3V signaling at all. However, thanks to the universal AGP motherboard standard (part of the AGP 2.0 specification), support was added. Universal AGP motherboards support both, 3.3V and 1.5V signaling.
But lately, motherboard manufacturers stopped to implement this standard, meaning that video cards using 3.3V signaling are not supported anymore. Due to the fact, that AGP 1.0 video cards havn't been around for years, this shouldn't cause any trouble. However, some AGP 1.0 compatible video cards using 3.3V signaling, have been sold as AGP 2.0 compatible and alrealdy destroyed dozens of motherboards.
In order to prevent operation other than AGP 0.8V, Intel now specified an additional electrical ID for AGP 3.0 compatible slots and motherboards. However, the specification doesn't make any statement about using video cards with AGP 3.3V signaling in an „Universal 1.5V AGP 3.0 motherboard“, supporting 1.5V and 0.8V signaling. Eventually, it's not clear whether AGP 3.3V video cards can cause major damage to „Universal 1.5V AGP 3.0 motherboards“

Speaking of AGP 3.3V: Since this almost antique signaling hasn't been officially supported since AGP 1.0 and hasn't been used by video cards for a long time (the last know artefacts are the SiS315 and few nVidia TNT2 video cards), Intel completely removed it from the AGP 3.0 specification. Still, motherboard manufacturers do have the possibility to implement the „Universal AGP 3.0 motherboard“ standard, in order to re-add support for those video cards. Additional information about the compatibility between AGP 2.0 and AGP 3.0 can be found in the eponymous chapter later on.