r/osdev • u/NoTutor4458 • 14d ago
why do most hobby os devs boot with BIOS?
i don't understand what's the point of developing os if you can't run it on modern hardware?
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u/zid 14d ago
You absolutely can run it on modern hardware though?
And as for the reasons:
You need a second, PE toolchain.
Few pre-available bootloaders support UEFI.
Your OS needs to support FAT32 where it might otherwise not need to.
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u/istarian 13d ago
Supporting the FAT32 filesystem is still a smart idea if you want to exchange files with an x86 PC, because it's relatively simple and is widely supported.
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u/kyr0x0 11d ago
It's copy and paste of a few hundred lines of code
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u/istarian 9d ago
Ok?
I'm just saying that there is some meaningful benefit to supporting a simple, common, well-defined filesystem even if you don't strictly need it.
Implementing it yourself from scratch is of more benefit if learning is the objective. And copy+paste could potentially introduce obscure bugs if you don't choose the source carefully.
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u/mishakov pmOS | https://gitlab.com/mishakov/pmos 14d ago
Because of the proliferation of bad and outdated tutorials and questionable recommendations (e.g. starting with x86-32, etc.)
This should be irrelevant as you should be using a bootloader anyway, and all major bootloaders/protocols (grub/multiboot2, limine, hyper, etc.) can boot with both
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u/Ok_Bite_67 13d ago
This! Except I think its also important to note that most people arent creating Operating systems that are going to be distributed. They are doing it to learn and the bootloader is an extremely important part of the process. Create your own if you wanna know how they work but before you run it on your own hardware its probably better to swap it out.
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u/mishakov pmOS | https://gitlab.com/mishakov/pmos 13d ago
Imo it's not very important, and the only thing you're learning are the quirks of PC firmware, which are irrelevant for kernel development
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u/Adventurous-Move-943 14d ago
It's probably the remainder of old times, it's been passed down like that for decades, UEFI still too modern for this.. You won't learn much on UEFI and still UEFI has to undergo all the transitions you'd do during BIOS boot, it's a nice practice. But yes to deploy your kernel you should aim for UEFI now, although a dual boot might still be a good choice.. UEFIs standard text output has tragical performance, when you boot in it and print some boot info you'd be surprised 😀 especially on modern devices with HD resolutions
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u/TheAtlasMonkey 14d ago
UEFI 2.0 is older than some people here.
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u/Adventurous-Move-943 14d ago
Well apparently BIOS rocks 😀 what can I say, people love it..
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u/TheAtlasMonkey 14d ago
B stands for Basic.
people don't love it... it the fastest way to show off in this sub.Most of them will fold once you speak about real hardware and metal.
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u/Adventurous-Move-943 14d ago
Yes but what do they show off ? A hello world kernel 😀 still they want to have fun and feel like hackers, why even bother. Trying to build an OS as a single guy is suicidal either way.
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u/antara33 13d ago
Or delusional, like Temple OS case
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u/istarian 13d ago
The only delusional part I can see us if you think you are developing something that other people will actually use on a day to day basis.
Realistically you are developing something for yourself. If you're lucky you might get some other enthusiasts to try it out.
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u/Brilliant_Trifle1915 13d ago
BIOS is easier to understand, and most people do osdev for fun
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u/thewrench56 13d ago
I dont see how BIOS is easier... UEFI is pretty darn straightforward once you understand how the structs can be used to invoke functions...
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u/paulstelian97 14d ago
My Frame.work with the Ryzen AI 7 350 can be configured to boot BIOS operating systems. Pretty damn modern, y’know?
Virtual machines support MBR boot just fine, even some are recommended to be MBR to avoid certain potential issues. I only see UEFI/GPT on physical hosts and on Windows guests which require it.
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u/Difficult_Inside8746 13d ago
Why would it be a requirement to run on a specific platform?
Using the legacy BIOS or running only in a VM doesn't matter, that's orthogonal to operating system development. If someone wanted to it would be easy to change the platform later on if the system is worth it.
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u/kiderdrick 13d ago
It's easy to get started with and a lot of people are not developing for modern hardware, they are devleping for QEMU.
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u/PseudoFrequency 13d ago
My hobby projects all use Uboot on ARM and device trees so it's not as universal as you think.
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u/Ruby7659_OSDV 13d ago
UEFI is modern, but being modern isn't always a good thing, because I think the path it takes you down in osDev is more challenging. There's a wealth of information about BIOS in resources related to osDev; it's been the standard for many years, and with so much resource availability, it's much easier for a beginner osDev developer who doesn't know what to do.(at least, in my opinion)
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u/motherisyuckeringyou 14d ago
idk about other people but I target the i486dx\ and while yea, elf32 does exist, I have never seen a 486 with UEFI\ and anyway\ uefi is bad (made by microslop) /j
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u/compgeek38400 13d ago
Why is UEFI 'bad'? Any reason besides its parents?
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u/istarian 13d ago
Secure Boot is problematic if you like freedom and want to be able to run whatever you want on your own computer.
It would be less awful if Microsoft's signing key wasn't so crucial...
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u/compgeek38400 13d ago
You dont have to have that for UEFI. So what is wrong with uefi itself?
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u/istarian 12d ago
I think you're looking at this the wrong way, personally.
What functionality does UEFI offer that the PC BIOS does not? If you aren't targeting modern hardware why bother with UEFI?
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u/compgeek38400 12d ago
I am targeting modern hardware, but even id i wasn't. I find UEFI way easier to use. Mostly for the memory map, but now ACPI (i may have the acronymn wrong, im in the garden)
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u/d0pe-asaurus 13d ago
The physical machine i test my stuff on is a some FM2 computer with no UEFI, and attached storage.
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u/letmehaveanameyoudum 13d ago
because it was easy and was literally the default
QEMU defaults to UEFI
most guides use BIOS
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u/Ok_Bite_67 13d ago
A lot of desktops still include compatibility layers that allow you to boot operating systems that boot with BIOS. Beyond that you can just swap your boot loader with a boot loader like limine thats supports UEFI in like an hour.
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u/istarian 13d ago
You frequently have to disable Secure Boot though and you probably shouldn't expect  a UEFI CSM (Compatibility Support Module) to provide all of the functionality the classic "PC BIOS" does.
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u/Ok_Bite_67 13d ago
Great addition of info! I rarely use the CSM so im unaware of its limitations. I just knew it existed and there was some support for legacy operating systems. When i make an operating system I typically just use limine unless im trying to learn something specific. (I always get a shell OS working but never get too much past that ADHD and all)
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u/istarian 11d ago
I'm sure the CSM supports enough functionality to properly boot up a system, but most modern operating systems provide their own hardware drivers (don't rely on BIOS or UEFI) and will probably reinitialize hardware as needed.
As far as I know, MS-DOS actually made use of the BIOS for it's own needs. Plenty of software running under MS-DOS worked direcrtly with the hardware though.
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u/burlingk 13d ago
It's probably because there are decades worth of tutorials for BIOS based systems and UEFI is still fairly new.
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u/xX_WhatsTheGeek_Xx 8d ago
UEFI is microslop garbage and I dont want to use someone else's bootloader.
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u/Agreeable-Lab-7079 8d ago
for fun, and it makes it easier to test for many people who only have shitty old i686 computers (like i do)
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u/TheAtlasMonkey 14d ago
Because `The framebuffer people`, just want to have fun.
Then you play GTA , you don't select the best weapon or the best vehicule, you just speed run it.
The problem arise when you start or behave like you are a gangsta.
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u/kyr0x0 11d ago
The framebuffer people can implement GTA 1 and even GTA 2 in framebuffer mode just fine.
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u/TheAtlasMonkey 11d ago
No they cant.
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u/kyr0x0 11d ago
Lol, yeah you can't - that doesn't mean we can't. The earth doesn't revolve around you.
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u/TheAtlasMonkey 11d ago
You cant either. The llm does it for you.
The fact you never left the framebuffer shows you just vibing.
You will never land any commit in a real os with this shitty attitude.
I did.
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u/davidinterest 14d ago
Sometimes people just develop for fun.