The IOP331 has a processor core speed of 800MHz, supports 133MHz 64bit PCI and supports up to 2GB of DDR RAM. The IOP331 is very similar to the Iyonix's IOP321 and is said to be "code compatible" with the IOP321. This means a 32bit RISC OS and third party software need no changes to run on the IOP331, however the pinout of the chip will most probably be different.
The IOP315 is more modest with a core processor speed of 733MHz, 133MHz 64bit PCI support and support for up to 12GB of dual ported 200MHz DDR RAM. The IOP315 is actually a two chip combination, bringing together the 80200 and 80314.The two new chips do seem to show that Intel is still interested in XScale powered processors and enjoys touting the low power nature of the chips and the ARM compatibility. It also shows the range slowly creeping towards the 1GHz boundary which is what we all dearly want.
Links
Intel IOP range
Possible ARM cores for RISC OS
What's an XScale?
Thanks to Steffen Huber for first spotting the new devices