Itsy-OS: A simple 380 byte OS kernel

http://www.retroprogramming.com/2011/03/itsy-os-simple-preemptive-switcher.html

by impomatic • 15 years ago

88 8 15 years ago

DrJokepu2• 15 years ago

Really cool experiment, although a bit difficult to extend as there are only 132 bytes remaining for loading anything else from the disk, which is not much (the boot sector is normally 512 bytes long on x86).

wtallis• 15 years ago

The demoscene notwithstanding, anybody counting bytes like this will probably be putting their OS in flash/ROM, not on a hard drive.

simcop2387• 15 years ago

It's even worse if you use the "standard" DOS partitioning system, only 440 bytes are available. (446 if you get fancy)

sgt• 15 years ago

Correct me if I am wrong. Isn't it likely that you would create a quick bootloader in the 512 byte long boot-sector, and then load this Itsy-OS from storage (e.g. flash, ROM, etc). Ofcourse it would require the bootloader to be written...

DrJokepu2• 15 years ago

Normally you would be right but I think since we're talking about kernel code golf here, it's only fair to consider the bootloader (if there's any) as part of the kernel.

tomjen3• 15 years ago

Actually all you would have to do would be to load the next n sectors and jump to the beginning.

Thats easily done in 132 bytes.

_b8r0• 15 years ago

You could pack this into a kernel loaded from Grub and pack a fair amount more in.

chrisjsmith• 15 years ago

I really like this. It's a good bootstrap environment for a kernel or scripting language of sorts. You could just about squeeze something to pull a block or two off disk with the BIOS on the end and kick off something more complicated.

Will have to dig out bochs tonight :)

Itsy-OS: A simple 380 byte OS kernel

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