1280 SHRES mode and exploiting the fact analog CRT TV wont be able to display this and interpolate down to 160 pixels worth of ~80 colors. The key seems to be bad TV and sitting far away :) Only one bitplane is filled with actual color data, 1280 / 8 = 160, all other bitmaps are prefilled with special patterns, system bus is heavily saturated leaving very little for CPU.
This gave me different idea instead of smearing colors on TV. 2x RP2040 pico. One soldered on top of Hybrid/DAC where it accumulates digital data 8 clocks at a time and automagically translates planar to chunky, second RP2040 playing a role of DAC. Sprites not supported for obvious reason, need all the pixels pushed out to reconstruct flat chunky data. 2x pico because one doesnt have enough pins to fit everything, and fpga/cpld uneconomical in the face of $1 RP2040s.
OCS/ECS Hires 640x @16 colors would produce 320x200@256 with zero performance penalty out of A1000/500.
Afaik Commodore Akiko chip was so braindead it took chunky data in and translated that into multiple planar writes to ram killing any potential speed advantage.
> Afaik Commodore Akiko chip was so braindead it took chunky data in and translated that into multiple planar writes to ram killing any potential speed advantage.
Even worse than that it didn't write them to ram - you had to read the planar data out of the registers and write them to ram yourself
> 4 bitplane 640 pixel scanline to output a 320 pixel 256 colour mode
yeah, you are right with 320. Means no need for any soldering inside Amiga, can just plug into Video Connector like A2024 monitor, and one RP2040 is enough.
> I vaguely remember a device back in the day
me too! I think it was dedicated to Video processing? or maybe bundled with a scanner? and most likely required you to massage bits on computer side.
Yes! I definitely also saw this one long time ago. Most likely my "independent" idea from post above was my brain just re creating this very product from memory :] GAL, few TTLs, SRAM? and a DAC, easy and cheap to manufacture and obvious once you saw IMS G171 being released in 1986 (year before vga). Another missed opportunity by Commodore, A500 should have had a socket for INMOS G171 right on the motherboard in 1987, maybe even a flap on top of the case for easy upgrade access.
Today $10 RP2040 pico board and a resistor ladder can implement it easily.
