x86 Bare Metal Examples: Minimal operating systems, learn x86 system programming

These are good examples and this might be slightly off topic but I wish that there were more resources on how modern x86 platforms actually work instead of using these legacy interfaces that are either emulated in SMM with IO port trapping or relegated to requiring chipset hacks to keep them working (such as VGA device hacks in the PCI spec or well known chipset legacy IO ports decoding to the LPC bridge).

While it is essentially impossible to truly understand every aspect of todays platforms I think that one can build a lot of intuition about how things work by studying how transaction routing is handled in the platform, e.g. how the uncore and chipset routes TLPs (whether it's raw PCIe or packets essentially wrapped by other interconnect protocols like IF/HyperTransport/DMI/QPI/etc) through the system with various base address registers and decoding windows. This gives way to understanding how modern MSI interrupts and DMA works as well. While I understand that truly going into things like PCI configuration, ACPI, UEFI, chipset interfaces on bus 0, modern booting, DMA and interrupt remapping, DRAM, register locking and security, security processors, power management, various types of runtime firmware, etc is a a many-years-long exercise I think that the core ideas don't need to be spread around all over the place for one to get familiarity with the ideas and patterns that underpin our PCs.

I think that a general conceptual overview on which one can hang more detailed knowledge acquired by reading specs is needed with the amount of complexity that exists today. There are some really good resources that I've collected over the years but there is still something missing. Maybe I or someone else will get around to it some day.

Nowadays, it's better to use x86_64 only. The 32 bit x86 has many drawbacks. The 64 bit is much cleaner and better in many many ways.

``` -no segmentation, flat address space -better interrupt handling -better system call -more registers etc.

``` Also we found that Qemu or other Virtualization technology may cover up some of the hardware issues. Eg. Beside, that every hardware device (keyboard, usb, display, disk etc.) will have some simplified behavior, if you emulate an ARM cpu on x86_64 host, than the cache coherency will totally messed up on real hardware.