It is not surprising that Radeon 9700 is an AGP 8x part, as all new 3D chips today follow this new standard. AGP 8x is not exactly an exciting specification, as it merely doubles the already meager 1 GB/s bandwidth of AGP 4x. Still the 2 GB/s of AGP 8x will improve the bottleneck situation for vertex transfers from the host to the graphics chip for a little while.
The Memory Controller
As I already mentioned, Radeon 9700 will have a 256-bit wide memory interface, making it the second 3D chip after Matrox' Parhelia to utilize an access path of this size to its onboard memory. The DDR-memory will be clocked at 310 MHz or something close, offering a bandwidth of 256/8*2*310 = 19,840 MB/s, or 19.4 GB/s (1 GB = 1024 MB for those of you who don't work for a hard drive maker).
Just quoting the raw bandwidth doesn't do the new memory interface of 'R300' justice. Finally, ATi has followed NVIDIA's example and included a crossbar memory controller that divides the 256-bit wide memory interface into four sub-units that can access the memory separately, making memory accesses more efficient.
Radeon 9700 will be able to be equipped with up to 256 MB of onboard memory, but the initial version will come with the lately common 128 MB.
R300 has already been designed with the new DDRII memory type in mind, so that future cards can be equipped with this upcoming memory type as well, once it becomes available.