My understanding is that the HSTX can do twice the bit clock as the frequency of the CPU, as opposed to 1x for RP2040. So 800x480 (60Hz) is possible with no overclocking (295MHz bit clock) and Luke said [1] he got 1280x720 50Hz with overclocking (530MHz using CVT-R according to the video timings calculator [2]).
Especially with the HSTX block which can apparently output at double the system clock (while the rp2040 was limited to 1/10th of the system)
If my rough math is correct, it should be possible to do output 720p 60hz video with an overclock to ~320Mhz. Though, actually generating that many pixels might be hard when you have nowhere near enough memory.
I would love to see some solid infomation about how well the rp2350 overclocks, apparently 300mhz is easy. 60hz 1080p is almost certainly out of reach, it would require something like a 700mhz overclock, but 30hz 1080p is probably viable.
> Though, actually generating that many pixels might be hard when you have nowhere near enough memory.
Even if you don't have enough memory or CPU time to render true 720p, it's nice to be able to output 360p or 240p inside a 720p container with each pixel and line duplicated two or three times. Doing it that way gives you nice crisp pixels rather than the blurry mess the displays internal upscaler would probably produce. You can even insert blank lines to get a faux-CRT-scanline effect.
And HSTX is actually pretty flexible. Nowhere near as flexible as PIO, but it can repeat pixels by itself (though, it uses the shift, so you can either pack multiple pixels per 32-bit word, or repeat pixels, not both).
Scanline doubling/tripping and blank line inserting can be done with nothing more than DMA chaining.
The two chips I have will both run at 350MHz with Vcore at 1.3V. No glitches seen. I am not sure how safe it is to run with that Vcore for long though. Probably fine. Stock Vcore will take you to 300 seemingly on all instances of rp2350
What kind of retro computing are you doing that would work well with high definition (720p). Standard definition I believe only started to be limited around 2007 when Xbox games like Dead Rising had captions that where too small to be legible on SD tvs
