Long ago, before access to the Internet was cheap and plentiful, and way before search engines made finding this kind of information easy, this was a priceless find for an aspiring low-level programmer. All the (semi-)common PC hardware and software documented in one place.

Endless hours spent exploring VGA hardware registers and trying to apply them for cool visual effects. Learning how the then-new 32-bit Windows interacted with DOS extenders, and trying to make a homemade - very basic - operating system that could do it, too. The thrill of writing a Terminate and Stay Resident alarm clock, and having it finally not explode...

I have very fond memories of the Ralf Brown's Interrupt List.

There was unloved informatics in school and loved informatics at home. Unloved informatics consisted of graph flow optimizations. Loved informatics consisted of EGA programming and IRQ interrupt handling for multiple keypress detection and other stuff. Both informatics were in Turbo Pascal, but in sport olympiads going to interrupts or assembler was prohibited. Not that it was going to help, but… when olympiads end, I was going those doors again, and others did not. For others my loved informatics was door remaining shut.

20 years later it is an excercize to find a device where loved EGA programming tricks work. Only unloved informatics remained

This was, and for some purposes still is, one of the most useful documentation sets for the PC architecture. It's worth noting that Ralf himself isn't a specialist low-level programmer, as this came from an era when there was a far smaller divide between users, power users, and developers.

For those way to young to even know what this is, it's basically like MDN web documentation but for the DOS era. It was a community-maintained API reference for IBM PC hardware, DOS operating system, and other software.

Oh the memories :) I still have somewhere a dot-matrix printed copy of the list I used religiously in the 90's

I wonder how things were done in this thing: https://en.wikipedia.org/wiki/Sun386i

Was that DOS emulation running some real DOS that though it was invoking BIOS calls?

According to a HN submission 3 years ago, evidently, Peter Norton once wrote a book on the 386i:

https://www.amazon.co.uk/exec/obidos/ASIN/0136616127/ref%3Dn...

I too have spent hours of assembly code on PC hardware. My freshly downloaded copy of the interrupt list has always been at my (virtual) side when designing tests or libraries.

I think that has been one of the very first and largest information collection shared for free on the internet.

Kudos to Ralf Brown and whoever participated in keeping the list compete, accurate and timely.

I'm not quite old enough to have needed to use this while writing my own software. But I've come back to it repeatedly while learning enough about the operation of DOS PCs to try my hand at reverse-engineering some games. That was at least 10 years ago. (It became clear that I'd bitten off more than I could chew, so no full game RE, but I documented a couple more file formats, wrote some file viewers, and learned a lot).

HTML version if you're just curious about what it looks like (all the links on the linked site seem to be zip files).

https://www.ctyme.com/rbrown.htm

This was invaluable when I was tasked with writing a stay-resident boot loader just after the turn of the century. Even then, such information was considered arcane and Ralf Browns Interrupt List was much better than any official documentation I could find.