6502kernel (OS for 6502-based systems)

[pulsar cargo]

https://github.com/AnnoyedArt1256/6502kernel

A simple OS for 6502-based platforms (currently C64 only), i'll port this to a future 6502-based computer i will work on in the future

[pulsar cargo]

so rn to prepare for the filesystem refactor, i first changed the file name limit from 64 to 48, so i could make the cluster size 64 bytes and have the rest of the properties fit in 16 bytes

next i will probably make the actual fat table

the thing is that i generate the FS with ca65 (macro assembler) macros

but thankfully ca65 is very flexible so i can generate and use vars/labels programatically with .ident

[pulsar cargo]

ok now i got the FAT table actually written at compile-time by ca65

now it's time to implement the required changes for the LAB_xxxx and fgetc functions to at least get sh to be loaded into memory and run grins

[pulsar cargo]

now the LAB_xxxx (and now fgetc) functions work with the new fs

and that makes fopen work as well

[pulsar cargo]

now, every syscall that accesses the FS is fixed to use the new fat-like fs

other than mkdir...

[lyric umbra]

Unix V1 on a C64?

[pulsar cargo]

kinda? it's not a complete unix-like but i did do some things in a more unix way

especially recently i've started doing syscalls and shit in a more unix-type fashion (using the same names and for instance)

[pulsar cargo]

finally, after 1.5 fucking hours of torture and screaming, mkdir now works in my new FS

all because of two lines missing from readdir breaking ls somehow 😭

[pulsar cargo]

and now 6502kernel works on my (currently very basic) 6502 computer emulator

it currently has 16k rom for the OS (which just uploads the kernel to RAM), a timer and a basic image reader (set address -> read from data reg)

[pulsar cargo]

i added a keyboard to the emulator and modified the getch syscall to use it and it worked first try 🔥

[mortal junco]

thats neat

running your os on your emu

pretty impressive

[pulsar cargo]

it's just a 6502, so emulating it is dead simple

but my 6502 emulator is cycle accurate

[pulsar cargo]

so, for the older C64 version of this OS i made a SID player that plays PSID files

but my new customer computer uses an AY-3-8910 soundchip, which makes the sid command useless

so i'm making a .pt3 player (pt3 is a format used a bunch of AY music trackers) that's for 6502

since most .pt3 players are for Z80-based platforms (the pt3 format originated from the zx spectrum, that's why)

[ionic yoke]

please port to BBC micro!

[pulsar cargo]

maybe if it has a timer IRQ :D

[ionic yoke]

it does!

you likely want 6522 VIA Timer 1

if I remember right

the one that drives the sound stuff

yeah 100hz event

[pulsar cargo]

so this channel has kinda been dead for a few days

but in that time i had been working on an super mario bros. port for my 6502 computer

since it and the NES use very similar CPUs

[ionic yoke]

yay, what about sprite hardware and stuff, do you have an equivalent, like a blitter or something?

[pulsar cargo]

i have 64 sprites with a 2bpp palette

each sprite can use one of the first 16 2bpp palletes in pallete memory (there's a total of 32 shared between the bg and sprites)

it's already playable btw, i just have to add/fix sprite priorities and add sound (since i use an AY-3-8910 sound chip and the NES uses a custom APU [audio processing unit] in the CPU chip [2a03] itself)

[ionic yoke]

that's really cool! are the sprites in layers or is it just whatever you call first rendered below?

because rn mario stands in front of pipes

like you said, sprite priorities

[pulsar cargo]

for now there's no layers, but i'll implement sprite layers in the future

it's my own 6502 computer anyway, i can add whatever i want technically

grins

[digital osprey]

neat, how are you keeping the hud in it's place? do you also have sprite 0 hit or is it just a scanline interrupt

[pulsar cargo]

i just use a scanline interrupt