Dennard scaling died. The issue I think is by the Intel P4/AMD K8 era, PC's had already hit that "good enough" threshold. For the average person, they need:
- Something that can browse the web
- Something that can type up a Word Document, Excel sheet, or a Power Point
- Maybe a few other apps, like video playback, nothing too CPU intensive
I mean, I as an enthusiast even seem to be reaching a good enough point too.
- Games (GPU more so than CPU is the limit there)
- Need something for video encoding (main reason why I am looking to get an X99 system some time next year)
- Bigger hard drives (video files take a lot of space)
I guess that in turn drives what I am excited about:
- SSDs, but not as much as before
- New hard drive technology
- GPU technology
It seems to me that single threaded performance has topped out. Let's say you had a 5.0 GHz i7 2600k @1.45V. So pretty decent luck on the silicon lottery. That 3.5 year old processor still is pretty fast. A 4.7-4.8 GHz Haswell chip today is not that much faster. It's only the things that can use the new instruction sets that seem to give decent per clock gains. Perhaps you can only optimize things like branch predictors to a certain level? Silicon too seems to be hitting its limits. If you think about it, the battle was always against heat and leakage. That and economics (fabs are exponentially more to build as the process goes down). But as you shrink, the benefits per shrink go down as you approach the atomic scale. It was inevitable that heat, leakage, and economics would win the day.
I personally am skeptical that new technologies will bring back, say Dennard scaling. Lately it seems a lot of promising stuff has gone the wayside. EUV, 450mm wafers, and the latest processes all seem to have issues. 20nm TSMC and 14nm Intel seem to be delayed and likely, problem plagued.
I think that there's still some more performance to be had from GPUs, owing to the parallel nature of the GPU. But my guess is that even that will hit the top.
After that, well, computers will be as exciting as maybe cars. Mature technology, and only some incremental improvements per generation. Maybe less than that even?