Raspberry Pi 4 OpenBSD based home computer/gaming console

[alehyze]

When I started programming as a kid, I had a Commodore 64 and later an amiga 500. Those machines came with very simple software and expected you to write some, rather than giving you thousands of pre-made packages to learn and play with.

A lot of existing software was video games. They were much simpler than those people play nowadays but they were still a lot of fun. Part of the fun was low latency.

I started working on a gaming console based on the raspberry pi that would have the kind of low latency that older home computers and gaming consoles had, and found a way to do that.

At some point, I realised that users would want to use a keyboard, read and write files, connect to the internet, stuff that is taken for granted with computers today.

So I wanted not to run on bare metal anymore, I needed an OS. Writing one from scratch would take me years and it probably would not be as good as an existing one.

But existing desktop operating systems tend not to be good for games, as they introduce latency and are able to stop a game at any time to do some other task, which can result in stuttering that the game developers cannot fully control or avoid.

I modified the OpenBSD kernel for the raspberry pi with gaming related extensions, in such a way that when the game runs there is no latency and no stuttering.

A game on my own fork of OpenBSD has the same performance of the bare metal code that I have written previously. And it can do file I/O, connect to the net and all that kind of stuff.

And when you quit the game it's just like normal OpenBSD so you can program it and make games yourself, browse the web and do all sort of stuff.

I am thinking that other people may want to have something like that, both for nostalgic reasons and for learning programming, so I thought of asking around and, if enough people like the idea, turn this into a product.

[notaplumber]

> I modified the OpenBSD kernel for the raspberry pi with gaming related extensions, in such a way that when the game runs there is no latency and no stuttering.

What does that even mean? What "gaming related extensions"?-- could you elaborate?

OpenBSD doesn't have any accelerated drivers for the GPU on the RPi, so I'm curious what your "no latency/no stuttering" modifications would even be, beyond perhaps maybe recompiling the kernel with HZ=1000 or something else..

[alehyze]

Without going into the details: I have read the linux drivers and understood how HDMI audio and hardware sprites (planes) work amongst other details. Then implemented that myself in C and assembly with no OS. Then modified the OpenBSD kernel in a way that it can use that stuff and do even more sophisticated stuff. This is not just recompiling the kernel with some different options. It's writing substantial code. I modified 6.8 because 6.9 was not even out when I started, so it's been a couple of months of very hard work on the kernel only, not counting all the time I spent on it before when I was working bare metal. And it's not finished yet :-)

[notaplumber]

This is HN, I'm sure people would appreciate hearing the details. Like how does this integrate with OpenBSD's existing audio/graphics stacks, do you plan to upstream your work? With it being OpenBSD, are there security implications?

[dr_zoidberg]

Well, he did say he wants to turn that into a product, so I understand he won't release details as they are a form of trade secret for his idea.

[alehyze]

I just released the "big picture". I am sure that the OpenBSD kernel devs can redo what I did ten times quicker (in terms of development time) and a million times better (in terms of clean integration with the kernel and security) if they want to. They know all of the details of the kernel :-)

That said yes, I would like to be able to turn this into a product.

[SLWW]

I'm interested in this; though i struggle to understand how you could turn something like this into a product.

There's a lot of logistics in selling this type of thing. Also the BSD license isn't exactly easy to sell something alongside of.

Have you considered open-sourcing and doing the ol' "if you like my work, buy me a coffee"

I know it's extremely communist of me, but I just can't imagine you not stepping on a lot of toes (both legally and otherwise) because of the spirit that OpenBSD was written in.

[alehyze]

What it does at the moment is a bit hacky, in that it does not integrate with the existing graphics stack in the way people could think.

I haven't written a driver for the pi graphics card or for HDMI audio. What I do with graphics is to save the existing state before beginning the game, do whatever I want during the game and restoring the state when it ends. With audio I am not doing it that cleanly as I believe that OpenBSD does not currently even touch HDMI audio registers.

As for the reduction of stuttering, when the game begins I stop 3 of the four cores, assign them entirely to the game ( also with new interrupt vector tables both in EL0 and EL1 ) and when the game exits give them back to OpenBSD. That way, while the game is running without interruption, the single core that is left to OpenBSD is free to run admin tasks. Since the game has a process that can be scheduled by that single core, the game can do networking or file I/O using OpenBSD, because the different cores have the same entries in the user space MMU tables and so they share memory and can talk to each other. OpenBSD cannot interrupt the game, it can only kill it if needed.

Regarding upstreaming my work the answer is "Probably not. But if the world wants it open sourced I am not against it and could think about doing a fork (Say we call it OpenBSD4Games). Or I could just give some help with the raspberry pi drivers."

The reason for that is that I am doing quite some stuff that am pretty sure the OpenBSD devs would not be happy to put in. OpenBSD is strongly focused on security. I am pretty sure they would not want to have some code in there that hijacks 3 cores out of 4 and gives them to a user process. Another example: I have been told that giving several contiguous memory pages to a user task is something that should not be done in OpenBSD. I understand why but then I give a game quite a few contiguous memory pages that the hardware will use for the frame buffer and so has to be contiguous.

Also, this is prototype code. It works for me, it still needs a ton of work and might not even be 100% correct. I cannot possibly understand all of the little details in the kernel in 2 months.

I am proud of this achievement though and would love to be able to turn this into a real product that many people enjoy.

Regarding the "home computer" part, I thought about game devs. When doing a game, it's not only the game code that is important. The tools are very important as well. So I built GNUstep ( on OpenBSD it does not currently work on arm64 ) so that it's super easy to build tools for game development in Objective-C.

Also I thought about playing around and experimenting, and I am planning a GUI app with GNUstep that integrates a C/C++ interpreter called cling, which is developed by CERN for their physics simulations if I am not wrong. With that, a game developer will be able to experiment with code and tweak it in a way that is similar to what Xcode playgrounds does with swift on the Mac.

[alehyze]

By the way, here is a video demonstration of all this. It's not very polished and VSYNC does not work, but it works pretty much how I describe here.

https://youtu.be/KhRnGbVhejk

[MonkeyClub]

Kudos to you, that's very interesting!

Could you share any resources you used to understand, navigate, and extend the OpenBSD kernel?

There doesn't seem to be much in the way of resources available on that -- nothing like the NetBSD Internals guide, not to mention the wealth of information on the Linux kernel.

A blog post on that would probably be widely appreciated as well, if you have the time :)

[alehyze]

Thanks :-)

The article that got me started is the pdf taken from a conference called "OpenBSD Kernel Internals: The Hitchhiker's Guide" mentioned here: https://www.openbsd.org/events.html

I just checked the link and the site seems to be down for me now, so I refer you to that page. Hopefully it will come back up or the link will be updated.

In that article it describes how to add a syscall to openbsd. So you start by writing a very simple one just to see that it works and get comfortable rebuilding the kernel and testing your syscall with a userspace program.

Then, since I roughly knew what I wanted to achieve, I started looking at kernel code and finding the parts relevant to what I wanted to do.

Then take baby steps with your changes, try and fail until you succeed with a small bit before moving on to the next. Especially value failures, as they give you hints about what is going on. Think why it could have failed and try a different approach that should not fail in the same way. Very tedious and time consuming, but a very good way to learn when you don't have the books.

Then looked for hints on the web and talked to the awesome people on the mailing lists and on the reddit OpenBSD channel.

I did not talk too much to people though, I asked a few questions at the beginning and then had a short conversation about allocating contiguous physical memory to a userspace task, which is something that OpenBSD does not do. I figured out how to do that by myself, by trial and error. Same with other details.

My mindset was: I know how to do this with bare metal, there must be a way to connect to the kernel code and do the same in a way that does not break things too much if I keep it limited in scope.

I hope this helps :-)

[MonkeyClub]

Yep, this is quite nice and helpful, many thanks!

[alehyze]

:-)

[onurcel]

On my TO-DO project list, there is "BASIC compiler/interpreter for raspberry(-like) computers".

I am nostalgic of Commodore64 too.

The thing that made many of us go down the rabbit hole was the immediacy of the interpreter, begging you to enter some commands 2 seconds after turning on your computer.

The perceived small gap between the commands you enter in a programming language and the games you could play with the machine contributed largely to the curiosity and willing to learn more.

On a modern computer, building the right interpreter is challenging. There is a trade-off between the simplicity of the language and what you can achieve with it. You won't impress today's kids if it allows you to only print text on a scrolling page.

But I think one can build something really great. There could be an integrated sprite editor (with a graphic UI) and the interpreter can use them right away with something like: Sprite1.visible Sprite1.x = 10

emphasising again the immediacy. Those "sprites" could be 3d objects as well.

[xeeeeeeeeeeenu]

You can configure RISC OS to boot directly into the BBC BASIC interpreter: https://www.riscosopen.org/forum/forums/5/topics/15793

[sleepybrett]

Yeah there is something really special about essentially booting into a basic prompt/interpreter. You get some of that from booting into a bash/zsh/sh/ksh/blah shell, but it's not quite the same.

[alehyze]

As mentioned in another comment, I am planning to add a C/C++ interpreter and I have put GNUstep in there, so that people can easily build their sprite editors and other game dev tools :-)

[0-_-0]

Something to look at if you want to encourage simple game development is supporting PICO-8 [0], or the compiled Nim version Nico [1].

[0]: https://www.lexaloffle.com/pico-8.php?page=faq

[1]: https://github.com/ftsf/nico

[alehyze]

Thanks :-) I like especially the pico-8, as it's fairly easy to write an emulator for that, as far as I understand.

[0-_-0]

It's also way more popular, with lots of games. The most impressive one in my opinion:

https://freds72.itch.io/poom

[alehyze]

Yep, that's amazing!!!

And it illustrates perfectly why what I am doing is cool.

I played that game in the browser and it looks great. But the controls are quite a bit laggy. That is not the developer's fault, they cannot do much about it. The medium that they chose is not designed for low latency.

My project enables developers to make a game like that more fun when you actually play it.

[OldHand2018]

What you’ve written is interesting and I hope you are successful. That said, I can already buy a Raspberry Pi at MSRP (sometimes even less). If I do that, I get access to a lot of software at no cost to me.

Low latency is great, but not a reason to pay more than MSRP. You’ll need to show me why it makes a difference and why it is worth paying the extra money. Also, I already have a Raspberry Pi 4 - can your “product” be added on to the one I already have?

[alehyze]

Thank you for your reply :-)

First of all, consider that I am just a guy who usually programs for a living and has been in a personal situation where he could not work. For some time I had an idea in my mind about this stuff and instead of getting depressed about not being able to work I went for it and started making it.

I am not asking for money at present, I am only asking for opinions.

My "product" is not a product yet, it's a prototype, there is no cost at the moment.

I clearly said in another reply that I am not even against open sourcing it, if that is what has to happen. Or maybe people will not be interested enough and forget about it. Who knows.

What I am saying is that I have spent quite some time working on this stuff and at the end of the day I have to pay my bills too, so it would be nice if I could make some people happy and get something back.

What worries me is that I genuinely believe that this is an interesting approach to "an operating system for games and game development" and I may not be able to sustain its development for much longer.

In its current form it can be added to a raspberry pi 4, yes, as this is what I have done myself.

Now for the question about why would you be interested. If low latency gaming is not interesting to you, then it would not be the product for you.

You are right, there is lots of great software out there that can be obtained at no cost.

That is true for everything. For example I don't watch much television so I don't use paid tv services.

[OldHand2018]

> Now for the question about why would you be interested. If low latency gaming is not interesting to you, then it would not be the product for you.

That was meant to be constructive :)

I enjoy typing and drawing on my iPad Pro, and one of the reasons it is enjoyable is that the iPad Pro has very low input latency.

The "low latency" thing is a bullet point on a spec sheet. What sells me is the enjoyable experience.

Your interesting approach is not what people are going to buy. They're going to buy what happens because of it. That's what you've got to sell if you want to sustain the development!

[alehyze]

> That was meant to be constructive :)

Uh, ok, sorry :-) It's just that I have been a bit upset by some other comments that made me feel like I am a bad guy only because I did something different and said it would be nice to make some money out of it.

> I enjoy typing and drawing on my iPad Pro, and one of the reasons it is enjoyable is that the iPad Pro has very low input latency.

You would be surprised. Apple has put a tremendous amount of effort to make their stylus low latency, and they did a terrific job. The latency is good for handwriting and drawing, or for typing. But for games I believe that there is still a very long way to go. Early machines had a solution that worked very well but the industry evolved in a completely different direction.

> Your interesting approach is not what people are going to buy. They're going to buy what happens because of it. That's what you've got to sell if you want to sustain the development!

You're absolutely right about this. I am painfully aware of this. I have many years of "interesting approaches" that go nowhere for lack of ability to connect with people on that level.

You know, different people have different abilities. There are exceptional people who are good both at their craft and at selling it, some only at their craft. Picasso and Van Gogh, Edison and Tesla, Gauss and Galois.

I am hoping to connect with other people, with experience in the area of selling and communications.

But more practically, there are a few places to get started. One I am looking at is the retro gaming space. Input latency is a big deal there. If I can manage to give people a low latency retro console, they are going to be interested. I have to customise an existing emulator, which I will be looking into after this round of "marketing", i.e. posting about my project on social media.

[penguinlinux]

this could be a great project. also the raspberry pi is very affordable. However, i think the best raspberry pi would be the raspberry pi 3 as the raspberry pi 4 requires a different ac adapter with usbc c and also a special hdmi cable so that increases the price of entry.

Even writing a game system for the raspberry pi zero w would be amazing.

[alehyze]

True.

The fact is that the zero does not have the computing power I want. The 3 does not have USB3 and that is a big issue for another reason.

It has to be the raspberry pi 4 :-)

[stuaxo]

Better to aim for the 4, as I assume it'll take some time to get everything done, the price will come down later on anyway.

[alehyze]

At the moment there is no "price", as there is nothing to sell :-)

I am only looking for people's opinions now

[vizzah]

You should turn it into the project.

I miss that mojo of old simple games. Never thought latency on modern OSes could be a barrier.

[alehyze]

Latency is a huge barrier, and it does not come only from OSes.

For example, modern television sets have a "gaming" mode because in normal mode they somehow process the video frames to make them look better, in a way that introduces latency.

Someone who works on audio software told me that audio over bluetooth has a very high latency too.

There are several bits that can introduce latency in a system. The OS is the part that software developers can adjust and improve.

[gbrown_]

For those intertested OP's blog and prior submission [1][2].

> I am thinking that other people may want to have something like that, both for nostalgic reasons and for learning programming, so I thought of asking around and, if enough people like the idea, turn this into a product.

Is a HN post the place for this?

[1] https://raspberrypi4gameconsole.blogspot.com/

[2] https://news.ycombinator.com/item?id=26544635

[alehyze]

I am sorry if people feel like this is not the right place for this post.

If the admins feel like that, please remove the offending post(s). Or ask me to amend them.

I have made something that I think is cool and with the hope that others liked it, but if it's out of place I can only apologise.

[detaro]

Not an admin, but this seems totally appropriate (resubmitting your blogpost would have been the more "correct" way, since HN generally prefers links over text submissions, but doesn't really matter)

Cool project!

[joshka]

IMHO, hn doesn't get enough of these submissions anymore. +1 cool :)

[alehyze]

thanks :-)

[alehyze]

thanks :-)

[Lewisssss]

I would be interesting only for performance reasons.

[alehyze]

Can you elaborate? What do you mean by "performance" ?