Other multitask GUI within 1 MB system software?

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Is there any other operating system besides AmigaOS that handles multitasking and graphics environment within 1 MByte?, preferably free.

Thinking that 512 kB ROM + essentials on floppy < 1 MByte. Memory protection could be worthwhile too.

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Well if the code is portable enough the choice of CPU is less critical. But one example would be a MIPS processor with 1 MByte RAM and 512 kB ROM and maybe some FPGA as graphics chip.

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Recal something like multi-TOS too ..

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cooperative multitasking.. hickuptasking

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Alternatives so far:
 * AmigaOS (m68k)
 * QNX 1.44M Web (x86)
 * MacOS from floppy (m68k?)
 * SymbOS for Z80 machines (MSX, Amstrad CPC / PCW) < 128 kB
 * Contiki (6502)
 * MenuetOS (x86)
 * KolibriOS (x86)
 * Multi-TOS (m68k?)
 * DOS + Win3.11 .. maybe??
 * GEOS 8-bit and 16-bit?
 * Early versions of GEM Desktop
 * Early versions of RiscOS

If I require pre-emptive multitasking, memory protection, GUI Window environment, free license, source code perhaps only KolibriOS fits?

I'm just thinking that a mobile phone shouldn't need 1 GHz CPU + 1 GB RAM to run software.... when an Amiga more or less did manage on 7 MHz CPU with 512 kB RAM in 1985. Time for Aphone (A-phone) that runs Amosaic on the town?
Also a laptop where one can compile and run C software with a battery that last a week would be something..

(just thinking freely)