You might be right about the bandwidth thing - been a while since I've read it - but it doesn't change the fact that crypto algorithms suddenly breaking (for non-brute-force reasons - again, you're saying it's bandwidth and not computing power) or AI suddenly becoming possible once you're saturated in a different mixture of nanomachines doesn't make sense.
I cautiously disagree with this, by the way:
>If you push any science fiction hard enough, you will find something impossible in the real universe.
What in Accelerando is impossible? Even more generously, what in it violates our current understanding of physics?
Faster than light travel. We do not actually know how to build computronium and it probably won't have the exact parameters given in the novel; real computronium may be many orders of magnitude less powerful. We do not know that living on Saturn is feasible from any engineering point of view. We do not know that there is any level of technology that will enable us to build a living adult human-like body in a matter of days as described in the book, as the ape manifestation of Manx was created. We do not know the limits of nanotechnology. We do not know that there is a path from humanity to post-humanity that still includes entities that were at one point human. We do not know what the limits of intelligence are. Is "Accelerando" really possible, or is it merely hiding in the unknowable more cleverly than older science fiction authors?
Bear in mind I often cite Accelerando as an example of sci-fi that is mostly possible (excepting the faster-than-light bit), but it's more that we can't currently prove it impossible than that it is guaranteed possible. We can't eliminate it on scientific grounds but there will be engineering limits in the real universe, too, and there's no guarantee that anything like that is actually possible. And the probability that the social implications of everything Accelerando laid out are correct is effectively zero, no offense to Stross, as nobody can really work it out.
We further do not know that we are not actually living in a simulation in which the "magic" parameter is merely set to 0, but switchable tomorrow on the whim of the Great Simulator. If you do not like the Zones of Thought today, well then the Accelerando-computronium can simulate it adequately enough to meet the criteria of the story one way or another. Given that this actually happens in Accelerand itself, I'm not even stretching; consider A Fire Upon the Deep as Accelerando fan fiction if it makes you feel better.
I'm advocating being a little more careful what nits you pick not because I'm a hippy who just wants to bask in the glow of the work, but because I've gotten to be a master nitpicker over the years. Nothing's perfect.
I cautiously disagree with this, by the way:
>If you push any science fiction hard enough, you will find something impossible in the real universe.
What in Accelerando is impossible? Even more generously, what in it violates our current understanding of physics?