Squeak ran in 2.8 MB with an IDE at about 1.6 MB. Minix might exploit the MMU (can theoretically be done at compile time) and it still uses synchronization queues, but its size is merit enough. 100 million SLOC is not all inlining folks. Optimization tricks by those like Jochen Liedtke make performance issues minimal. Imagine some assembly optimization like what was done with MenuetOS/KolibriOS, which fits on a 1.44MB floppy disk (GUI OS + applications)! Get that? Q: You have written the whole OS in x86 assembly. How much speed you think you gained by using asm compared to C or C++? Ville Turjanmaa: Parts of Linux was rewritten in assembly and the speed gain was 10-40%. That will give an idea. https://www.osnews.com/story/93/interview-with-ville-turjanmaa-the-creator-of-menuetos/