All FT8xx so far have 8k of memory for the display-list, that is 2048 32-bit words.
Expanding this to 64k would be nice on first glance but then everything still would need to be executed for every single frame.
So at the same time the chip would need to be much faster.
This reminds me of a different "issue".
The divider for the clock only works well for small displays.
800x480 is configured to 928 h-cycles und 525 v-cycles, that are 487200 clock-cycles.
A typical value for the divider would be REG_PCLK = 2 which means that a FT81x uses 30 MHz.
In return these settings result in about 61 frames per second, nice.
Now I have this 1024x600 TFT from Glyn.
For some reason (I suspect a flaw in the design on Glyns side) these can not be used with the full clock of 60MHz.
As these are configured to 1100x720 this would result in 75 frames per second anyways.
The recommended value is 20MHz and therefore 25 fps and they work well with 30MHz which results in 37 FPS.
The issue I have there is that the divider does not allow for fractional values, so I could not configure it to
use 45MHz for example which would result in 56 fps.
Now the upcoming BT81x uses 72MHz.
That is nice, so the 1024x600 panel could be used with 45 fps.
The 800x480 panel at REG_PCLK = 2 would run with 73 fps so we need to make that REG_PCLK = 3.
But then it would be clocked with 24MHz and "only" 49 fps.
If for whatever reason you would need to fine-tune the frame-rate you simply could not do that.
One could come up with the idea to manipulate the base-clock but the datasheet does not give a frequency range, the only allowable frequency is 12MHz.
The PLL could be changed to multiply by 2...5 (6 with BT81x).
At higher resolutions this would even become more of an issue.
Do I want higher resolutions or do I need them?
No, not really, I would be fine with 4 pixels per mm for HMI. Or make that 8 pixels per mm.
The typical 800x480 7" has 11 pixels per mm.
But what I need are bigger displays and there close to none 800x480 or 800x600 panels bigger than 7" out there.
And the bigger panels do not only have higher resolutions, they also typically do not have a RGB interface anymore but LVDS instead.