Show HN: My self-written hobby OS is finally running on my vintage IBM ThinkPad

I did that all my life: no unicorns but if you do enough things, some will sell auto (once any traction happens I sell: I don't like running a company, I like building stuff). Without all this stress and grifting. Granted, I was lucky that my hobby in 2000 turned out to be worth millions, but it still works fine 25 years later.

Linus' original plan was to write Linux to learn every feature of the i386. Compatibility with other systems came later.

See the message from Linus Benedict Torvalds on 26/08/1991

https://groups.google.com/g/comp.os.minix/c/dlNtH7RRrGA/m/Sw...

I'm not sure it's a bad thing to not necessarily have a plan. Intuition is the hidden sister of logic, both children of reason, and we don't always see her because she's often behind the scenes doing all the work.

Technical debt is as sure as death and taxes. Good software grows over time, like a person growing up. Sometimes you have parts that are needed for a time but not permanently, like baby teeth. That's what technical debt is like.

Other times there are parts that are absolutely ideal long term, but it's a long time before they even make sense. And sometimes things only develop much later than we expect, like wisdom teeth. These are software features that won't make sense until you write the thing that you don't realize yet is only temporary.

I have the same goal of writing everything myself from scratch. It's a very important goal to me for a reason I don't fully understand yet.

Congrats on writing an entire OS, and getting it booting on real hardware! That must be such a rewarding feeling in its own right, even if no one understood how. And it looks so very cool.

You've given me more motivation to announce my project soon. Maybe next week. Thanks.

Have you played around with Zig yet? I hear that would be a good replacement for C here. Did you have any thoughts on porting your OS to that, or did you have any branches some Zig code made its way into?

Regarding a plan, I often feel the same way about my own project. There are a number of systems I've rewritten multiple times, and I can't help but think much of that would have been unnecessary if I had been more tedious about diagramming out my needs and requirements beforehand. Other times I wonder if I would have gotten this far had I planned things out... It's the age old question of "would I have started this project if I had known how much time and effort it would have taken?"

Each approach has a clear set of pros and cons, as others have explored in this thread. In the end, I think what ultimately matters is whether we're satisfied (and proud) of a project after a significant amount of progress has been made.

I also took the "I want to write everything myself" approach with my project since I wanted it to be a demonstration of my abilities. I wanted to prove to myself and others I could create a project of significant size and scope. It seems like this often means working without libraries and having to reinvent the wheel over and over again. It's tedious, but it certainly adds to the satisfaction you get as you look over your work and think "this is truly mine; I did this."

And yes, copy ideas, not code, is one of those things I do my best to adhere to. Sometimes, at least with JS, you run into problems, look into solutions, and it turns out there's really only one sensible way to do something; what you end up writing feels like a boilerplate solution to the problem. I often find myself going back and forth through search results from places like Stack Overflow and trying to siphon out the best techniques and ideas from multiple examples to mesh together into some usable code in a style I prefer.

Finally, since I failed to say this eariler, congrats on your project! I'm gonna have to try it out as soon as I get some extra time.

I'd like to second the mention of plan vs. no plan.

Having no plan is often better when you're facing a deep pit of work, pick at it every now and again, whatever you feel like working on that day.

vs. having a clear Todo list that is longer than a DNA chain and just giving on it after item 5 because 6 is boring.

Oh, and congrats, looks great.

Curious about the less UNIX dependent part - did you find the UNIX model (everything is a file - or more accurately everything is a serial connection) to be a poor abstraction for a hobby OS?

I had the same problem, I made a 3x4 font that was just barely servicable for the initial project to show text on screen. It was my first (and only) font I ever made! Eventually I needed lower-case, so I turned those into lower-case and made a 3x5 variant for uppercase. It's still not ideal, and I'm sure when I announce my project, people will complain about it. So I've prepared to say "it's a stop-gap solution to make the OS servicable, but we can make more fonts."

I think people skimming a project often just don't quite get how much we pour into our projects, and how very much it cost us. But it's okay, they don't have to understand just how cool it is what we made. At least we know.

When I saw your video of your project, I was thinking to myself, "wow, that's incredibly cool, and I can relate to the steps he's doing!" Just trying to be the voice here of someone who thought that way, in case there are no others.

One can really get bogged down in fonts. (-:

http://jdebp.uk./Softwares/nosh/guide/terminal-resources.htm...

If you want a quick improvement over that 8by8 IBM ROM font, I suggest two things:

1. Switch to a 16by16 square.

2. For the ASCII range, go with one of the old home computer fonts, rather than IBM ROMs. Viznut has .hex files for Commodore PET and BBC Micro graphics modes squirrelled away inside Unscii.

I've done the work of upscaling the 8by8 PET font to 16by16, and it works quite nicely as a monospace square font. These old home computer fonts were of course designed to. Whereas in the world of VGA you're soon in trouble with glyphs designed for 9by16.

Supporting variable-width fonts is pretty easy on its own (if bit-packing, you might wish to store them vertically), but does complicate combining characters (remember, they go in different places and may need to make the new character larger).

For vector fonts, the interesting question is "if I render this at a different resolution and then scale it, will it line up?" which fundamentally has no answer that can satisfy everyone. Most other difficulties are merely a Small Matter of Coding (and providing appropriate APIs).

The fact that the OP built an entire hobby OS complete enough to have windowing and font rendering, and got it booting off his vintage notebook, is extremely impressive, and much more so than the ChatGPT frontends and Chrome reskins that HN usually enthusiastically updoots.

The power of the crowd compells you.

The power of the crowd compells you.

The power of the crowd compells you.

I meant it as sincere constructive criticism! :) <3

So what? Someone is not allowed to give constructive criticism?

An x86 disassembler is not that hard, as long as you stick to a single mode and ignore the SIMD alphabet soup.

You have a short loop that scans through the prefixes, checks for a REX prefix (if you handle 64-bit mode), reads the opcode (1-3 bytes), reads the MOD/RM byte if there is one (use a table lookup), reads the SIB byte if there is one (table), reads offset if there is one (table), reads immediate if there is one (table).

It's probably easiest if you use an "expanded/normalized" opcode internally so the 1-3 opcode bytes + the 3 extra bits from some MOD/RM bytes + prefix info (for certain SIMD instructions) map to a single 16-bit opcode (likely around a couple hundred to a thousand opcodes in total).

You have a table that maps those to mnemonics + operand info. You have some tables that map 0-7 (or 0-15) to AL/AH/... and AX/BX/CX/... and CS/DS/ES/... and various system registers.

Not that much code all in all. Several tables. You can squeeze them and bit pack them to your heart's content if you want.

Once you have that, a simple assembler isn't so hard.

I understood. Thank you very much for the information. It's definitely much helpful to me.

Really worthwhile goal no matter what anybody says :)

Did a little testing myself.

Tried it on some bare metal, looks pretty good.

There were two phases, wouldn't fit in a single comment.

Wrote RetrOS-32.img to a blank SSD and it boots in CSM/Legacy mode.

That's a nice milestone right there :)

This was on a tiny Lenovo desktop about as old as an x240. These are low-power, run on the same Thinkpad A/C adapter, so there are some similarities to a laptop.

But the cursor wasn't very responsive and wouldn't come down below the very top rows either so could not sign in. Using mainstream wired mouse & kybd. (The PC has 8GB memory, in the login box it showed the nominal 15mb, but extended memory was a negative number, about 8GB itself.)

Then I remembered things like the x240 often have a touchpad that is recognized as a PS/2 mouse, not USB. Moved the SSD to an old tower that has a PS/2 mouse and kybd and then could sign on. Cursor was still quite a bit sluggish, but it worked. This one has 12GB memory and the reported extended was about 464mb so it looked realistic in the login box.

It boots! It works nominally! It's some kind of Golden IMG already, so congratulations!

Back at the Lenovo I do boot to DOS from time to time, and I enable Legacy USB in the BIOS so I can use the USB mouse for DOS which had no concept of USB. After booting DOS, if I want to use the mouse I still have to load DOS mouse drivers, just like the 1980's but this firmware setting fools the old pre-USB DOS mouse driver so it will handle the USB mouse & kybd that people are using now. This setting has been there for ages since the PS/2 sockets on PC's started becoming scarce. Checked the BIOS, and Legacy USB was enabled the whole time.

However, on this Lenovo there was an additional setting, for "USB Virtual KBC Support". I don't know if I ever saw this along with Legacy USB settings in one BIOS, up to now would have assumed they were both the same thing but using different terminology. This setting was not only disabled by default, the text says this one auto-disables once an XHCI driver has been loaded. Then definitely found it to auto-disable after booting Windows.

Enabled Virtual KBC, booted to RetrOS and the USB mouse could log in. More sluggish cursor than on the PS/2 machine though.

Plus there were some untyped characters that would sometimes appear when logging in, or admin would duplicate itself so username said adminadmin after you typed in the password below.

Still has a huge negative number in the login box for extended mem, that was not a show-stopper, mem appears normal when looking at the system stats once logged in.

I would now imagine this Virtual KBC setting emulates how mouse & kybd are presented to a VM?

Interesting finding that DOS does not require this setting for a USB mouse to work on bare metal, but RetrOS does.

Have not put it through its paces thoroughly, focusing on the bare metal aspect.

Is that 4sec delay something introduce in the pi 4 or 5? At least one guy got the 3 to boot to a Qt app in 2.8 seconds: https://www.furkantokac.com/rpi3-fast-boot-less-than-2-secon...

I don't think Haiku runs on raspberry pi either.

Great, good luck :) It was a reference to the original Linux announcement in 1991,

> I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu)

Appreciate it!