mu/baremetal/README.md

Some apps written in SubX and Mu. Where the rest of this repo relies on a few
Linux syscalls, the apps in this subdirectory interface directly with hardware.
We still need the top-level and apps to build them.

I'd like to eventually test these programs on real hardware, and to that end
they are extremely parsimonious in the hardware they assume:

  0. Lots (more than 640KB/1MB[1]) of RAM
  1. Pure-graphics video mode (1280x1024 pixels) in 256-color mode.
  2. Keyboard

That's it:
  * No wifi, no networking
  * No multitouch, no touchscreen, no mouse
  * No graphics acceleration, no graphics
  * No virtual memory, no memory reclamation

Just your processor, gigabytes of RAM[1], a moderately-sized monitor and a
keyboard.

These programs don't convert to ELF, and there's also currently no code/data
segment separation. Just labels and bytes.

Most programs here assume `main` starts at address 0x8800 (3KB or 6 disk
sectors past the BIOS entrypoint). See baremetal/boot.hex for details.

So far the programs have only been tested in Qemu and Bochs emulators.

[1] Though we might need to start thinking of [the PC memory map](https://wiki.osdev.org/Memory_Map_(x86))
as our programs grow past the first 512KB of memory.
7403 - baremetal/ for apps without a kernel 2020-12-26 21:22:28 +00:00			`Some apps written in SubX and Mu. Where the rest of this repo relies on a few`
			`Linux syscalls, the apps in this subdirectory interface directly with hardware.`
7419 2020-12-27 06:56:44 +00:00			`We still need the top-level and apps to build them.`
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware. 2020-12-26 22:21:04 +00:00
			`I'd like to eventually test these programs on real hardware, and to that end`
			`they are extremely parsimonious in the hardware they assume:`
7406 2020-12-26 23:34:10 +00:00
7410 2020-12-27 01:35:16 +00:00			`0. Lots (more than 640KB/1MB[1]) of RAM`
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware. 2020-12-26 22:21:04 +00:00			`1. Pure-graphics video mode (1280x1024 pixels) in 256-color mode.`
			`2. Keyboard`

			`That's it:`
			`* No wifi, no networking`
			`* No multitouch, no touchscreen, no mouse`
			`* No graphics acceleration, no graphics`
			`* No virtual memory, no memory reclamation`
7406 2020-12-26 23:34:10 +00:00
7407 2020-12-27 00:37:10 +00:00			`Just your processor, gigabytes of RAM[1], a moderately-sized monitor and a`
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware. 2020-12-26 22:21:04 +00:00			`keyboard.`

7409 2020-12-27 00:38:47 +00:00			`These programs don't convert to ELF, and there's also currently no code/data`
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware. 2020-12-26 22:21:04 +00:00			`segment separation. Just labels and bytes.`

7418 - baremetal: adjust entrypoint address We need a few pages of data for the keyboard mappings. If I moved them to some later address I'd be able to keep the nice round starting address unchanged. But that seems like a superficial aesthetic concern. There's really no value in having an array of hex bytes represented in SubX rather than just raw hex. And it's better to colocate data near the handler code which uses it (and which runs instructions SubX doesn't support). 2020-12-27 06:33:48 +00:00			Most programs here assume `main` starts at address 0x8800 (3KB or 6 disk
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware. 2020-12-26 22:21:04 +00:00			`sectors past the BIOS entrypoint). See baremetal/boot.hex for details.`

			`So far the programs have only been tested in Qemu and Bochs emulators.`
7407 2020-12-27 00:37:10 +00:00
7408 2020-12-27 00:38:01 +00:00			`[1] Though we might need to start thinking of [the PC memory map](https://wiki.osdev.org/Memory_Map_(x86))`
			`as our programs grow past the first 512KB of memory.`