Hi, guys! I haven't been here for some time

I'm interested in starting a project consisting in making a very simple home-made computer and program an OS for it from scratch and I want it to be totally low level, pure assembly, direct access to hardware, no 3rd party software, no drivers, nothing, as simple and direct as possible.

What I want to do is pick a microprocessor I can easily find and interface with, make a board for it and connect it to whatever stuff and ports I want to give it. It can be a bare microprocessor or microcontroller if it's not too complicated to interface it or it can be a development board containing one as long as it gives me good access to it (some only give you a few pins). And my idea is to make the code using fasmg on my computer and then just uploading it to the hardware memory.

I've considered some PIC32s, some ColdFire and ARMs among others, but I get pretty lost and I really haven't done this before. Can any of you guys recommend me some hardware (microprocessor/microcontroller/development board) that I can use to begin with this? Thank you!

My 3 bits:

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mecrisp is a nearly professinal forth
http://mecrisp.sourceforge.net/

that i had running on this board:
https://www.conrad.de/de/p/entwicklungsboard-texas-instruments-ek-tm4c1294xl-1270206.html

It was recommended to me as beginner friendly (and it seems to be, i go it going )

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Minal-OS uses fasm for an OS from scratch:
https://codeberg.org/sts-q/minal

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regards

You should favor riscv CPUs... since they are royalty free for everybody around the world, even in barbaric countries.
(for exactly the same reason: do prefer displayport over hdmi, av01 over h265)

I don't beleive there are RISC-V cpus to buy sifive just sells t-shirts

Mikron MIK32 – Made in Russia 32-bit RISC-V MCU offers features similar to STM32L0 MCU

Price - about $6 (depends on the number of pieces and costs of the delivery).

Company's website: https://www.mcu.mikron.ru/

I want to buy it, where can I buy it?

Ah, it offers me to buy 20000 microcontroller boards
I see....

Is there any building/compilation guide?

Well, i think there is not.

All magic happens in this bash script:
https://codeberg.org/sts-q/minal/src/branch/master/minal
build-iso: copy assemble linking iso
start-vbox:

There are not too many preconditions and dependencies:
* quemu or VirtualBox
* This grub2-mkrescue thing
* ld
* fasm

( I do almost all with VirtualBox. In quemu it runs a lot slower. )

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Rabbit-vm
is an other approach to the same theme.
It is more mature, simple to install and comes with installation instructions.
https://bitbucket.org/sts-q/rabbit-vm/src/master/