Use of the Intel i915GV core logic is what really defines the 915-A's feature set. At first glance, it's hard to spot the difference between 915G and 915GV. 915GV doesn't support a 16 lane PCI Express bundle for routing to a PEG16X electrical slot, for graphics. With that electrical slot physically present on the 915-A, you'll notice the lanes routed to the slot, of which there are only two, are provided by the ICH6 I/O southbridge processor rather than the 915GV northbridge.

It also supports an AGP 4X/8X electrical slot, conjured up by similar black majiks (the bonding of two PCI hosts from the ICH6), so for the CPU to communicate with any discrete graphics card, be they in the faux-AGP slot or the PEG16X slot with only 2 lanes routed to it, the communication has to go via the 266MiB/sec Intel Hub link between i915GV and ICH6, since everything discrete graphics wise is connected to the ICH6.
http://www.hexus.net/content/reviews...lld19JRD0xMDcy