Xbox720 clocked speed low?

[SvennoJ]

What does this mean for backwards compatibility?
I've no doubt that modern day 1.6ghz multi-core cpus can outperform the 7 year old 3.2ghz xenon but what effect does that have on emulation?
Ps4 to come with a separately sold cell dongle, 720 with a Xenon dongle for bc?