richard herveille created one 16 years ago which can do the job. it's silicon-proven: ICubeCorp put it into their IC3128.
We could finally learn from this lesson and not support in any way any standards whose implementations require patent licensing.
Consider the Ericsson MC218 / Psion Series 5 (https://www.google.com/search?q=psion+series+5). The software (EPOC, forerunner to Symbian) could drag windows (whole windows) around the little screen faster than the LCD crystals could keep up/redraw.
I had a look inside the unit (find the photos at https://www.applefritter.com/content/pocketable-ultra-low-po...) and found only a 36MHz ARM7TDMI inside. Presumably the CPU was doing the window redrawing all in software.
It's really reassuring to me that such a slow CPU gave the LCD a run fo its money, because let's face it, doing $tons_of_pixel_manipulations on a CPU always chews power, so if you want battery life you're going to need something that works well at the low-power end of the spectrum. (The Series 5's monochrome LCD was 640x240.)
So, well-designed software would meet the power consumption-versus-feature challenge halfway. Such software doesn't exist yet though, and it appears this status quo isn't going to change anytime soon; the (financial) investment required just doesn't seem to be materializing.
I'd say the main problem is market effects, and consumer interest. "Yeah 70% of CPU time goes to drawing the screen" is NOT particularly attractive.
technically speaking it's perfectly possible to use an 8mhz 8-bit arduino-style processor to make a phone, if all you want is calls and SMS! the processor inside the actual GSM/3G modem is far, far more powerful than that.
i added up the number of actual processors in a smartphone once: it was insane. DSP in the Audio IC. ARM core in the GPS. ARM core in the 3G Modem. ARM core in the main processor. 8051 core in the capacitive touchpanel controller. the list just goes on and on!
FWIW, I did see a weird black blob type thing on the LCD ribbon cable, but I don't think I got any photos of that. That is very probably the LCD controller you speak of.
I wouldn't be entirely surprised if the main CPU (and specifically EPOC) had a framebuffer of what was on the screen. (I'd be surprised if it didn't have any such (double-)buffering.)
Yeah, baseband processors have a fair bit of oomph to them. I've long been curious what sorts of specs they have.
In the iPhone, there's also the ARM core in things like NVMe storage as well. (http://ramtin-amin.fr/#nvmepcie)
What law would that be? A patent holder can set whatever terms they want. Standards orgs try to impose FRAND for their contributors but it is not legally binding.
Designing a decent CPUs without violating any patents is easy. Almost all CPUs today follow design patterns which were established back in the mid 80s and early 90s. All those original patents have now expired and you can sidestep around the newer ones.
Things like GPUs have evolved massively since the late 90s, gaining support for pixel shaders, vertex shaders, moving to unified core designs, gpu compute and establishing new threading models.
And all these things have bled back into the Graphics standards. It would be really hard to design a gpu implementing even a 10 year old standard like OpenGL ES 2.0 without violating any patents.
And it will be even worse with things like pci-e, ddr and networking controllers. You can't design around the patents without breaking compatibility because there are standards enforcing you to follow the patents.