ack

> Even getting an OS, compiler etc is not that easy. There's a GCC fork [0], macro11 [1] (GCC and clang also both have macro11 backends), ack [2] and more. Getting hold of a modern compiler is trivial. > It's kind of hard to get hold of a PDP-11 these days. The PiDP-11 [3] emulator that runs on a Pi, is fairly popular among the retro crowd. So sourcing something hardware wise that behaves that way is easily possible. The Computer History Simulation Project [4] will give you easy access to simulating a PDP-11 on just about anything that you own. But if you want the original hardware, then they're in the $400-500 range, in my area. Easy to source. [0] https://github.com/JamesHagerman/gcc-pdp11-aout [1] https://gitlab.com/Rhialto/macro11 [2] https://github.com/davidgiven/ack [3] https://obsolescence.wixsite.com/obsolescence/pidp-11 [4] https

The Amsterdam Compiler Kit is also his work (along with Ceriel Jacobs): https://github.com/davidgiven/ack Just as Minix perhaps could've been Linux, The Amsterdam Compiler Kit could've been gcc, but for licensing issues: https://www.theguardian.com/books/2001/apr/10/firstchapters....

Also to note, LLVM isn't the first compiler toolchain of its kind. Notable mentions, IBM's research project on PL.8 while developing their first RISC designs. https://rsim.cs.uiuc.edu/arch/qual_papers/compilers/auslande... https://pdfs.semanticscholar.org/3288/fc042cd474f0ec93d67753... https://rishiheerasing.net/modules/hca2102/paper/cocke.pdf The Amsterdam Compiler Toolkit, http://tack.sourceforge.net/ https://github.com/davidgiven/ack https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.12... The more the merrier.

0000:7c00 (segment 0, offset 0x7c00) and 07c0:0000 (segment 0x7c0, offset 0) are at the same physical address of 0x00007c00, so the processor will see the same bytes each way. The latter's more useful in 16-bit mode, though, as it allows you to use offsets 0x0000 to 0xffff to access the 64kB of data starting at physical address 0x00007c00. So typically the first thing you do on entry to the boot sector is to do a far jump to change code segments. But you don't have to; if you're immediately switching to 32-bit mode it may not be worth it. Here's my boot sector --- everyone's written one. Mine's intended to load and run raw tiny mode executables on floppy. https://github.com/davidgiven/ack/blob/default/plat/pc86/boo...