2020-12-26 21:22:28 +00:00
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Some apps written in SubX and Mu. Where the rest of this repo relies on a few
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Linux syscalls, the apps in this subdirectory interface directly with hardware.
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2020-12-27 06:56:44 +00:00
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We still need the top-level and apps to build them.
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2020-12-26 22:21:04 +00:00
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I'd like to eventually test these programs on real hardware, and to that end
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they are extremely parsimonious in the hardware they assume:
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2020-12-26 23:34:10 +00:00
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2020-12-27 01:35:16 +00:00
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0. Lots (more than 640KB/1MB[1]) of RAM
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2020-12-27 16:33:22 +00:00
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1. Pure-graphics video mode (1024x768 pixels) in 256-color mode. At 8x8
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2020-12-27 16:03:48 +00:00
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pixels per grapheme, this will give us 160x128 graphemes. But it's still
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an open question if it's reasonably widely supported by modern hardware.
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If it isn't, I'll downsize.
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2. Keyboard. Just a partial US keyboard for now.
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2020-12-26 22:21:04 +00:00
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That's it:
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* No wifi, no networking
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* No multitouch, no touchscreen, no mouse
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2020-12-27 16:03:48 +00:00
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* No graphics acceleration
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2020-12-26 22:21:04 +00:00
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* No virtual memory, no memory reclamation
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2020-12-26 23:34:10 +00:00
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2020-12-27 00:37:10 +00:00
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Just your processor, gigabytes of RAM[1], a moderately-sized monitor and a
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2020-12-27 16:03:48 +00:00
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keyboard. (The mouse should also be easy to provide.)
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2020-12-26 22:21:04 +00:00
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2020-12-27 16:03:48 +00:00
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We can't yet read from or write to disk, except for the initial load of the
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program. Enabling access to lots of RAM gives up access to BIOS helpers for
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the disk.
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These programs don't convert to formats like ELF that can load on other
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operating systems. There's also currently no code/data segment separation,
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just labels and bytes. I promise not to write self-modifying code. Security
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and sandboxing is still an open question.
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2020-12-26 22:21:04 +00:00
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2021-01-09 23:38:03 +00:00
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Most programs here assume `main` starts at address 0x9000 (7KB or 14 disk
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2020-12-26 22:21:04 +00:00
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sectors past the BIOS entrypoint). See baremetal/boot.hex for details.
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So far the programs have only been tested in Qemu and Bochs emulators.
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2020-12-27 00:37:10 +00:00
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2020-12-27 00:38:01 +00:00
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[1] Though we might need to start thinking of [the PC memory map](https://wiki.osdev.org/Memory_Map_(x86))
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2020-12-27 06:57:16 +00:00
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as our programs grow past the first 512KB of memory. Writing to random
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locations can damage hardware or corrupt storage devices.
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