Great article

>>> When BIOS interfaces weren’t sufficient they hit the hardware directly - and even if they weren’t doing that, they’d end up depending on behavioural quirks of IBM’s BIOS implementation.

This happened with the Apple II as well, and made it impossible for Apple to update their system. Even minor changes, from the Apple II to the IIe and IIc, broke some apps. And if an app broke, it was presumed to be the hardware maker's fault.

There was a book entitled "what's where in the Apple II" that documented all known variable locations and entry points in the Apple ROM and DOS. For instance people would just branch directly into weird places in the ROM, or poke directly into memory.

Apparently this is Matthew Garrett's blog. It contains one article.

Looking at his more common blog, https://mjg59.dreamwidth.org/ ... it says he's moved to this one.

Any particular reason he's no longer using Dreamwidth?

> The truth is that there’s no way we can technically describe a PC Compatible now - or, honestly, ever. If you sent a modern PC back to 1981 the media would be amazed and also point out that it didn’t run Flight Simulator.

For historical context, a PC compatible is a machine that can run a DOS that is compatible with PC-DOS and that can run applications for the IBM PC running PC DOS. This was vital to the success and failure of many companies and thus we can absolutely say what a PC compatible was. The PC-compatible standard was largely replaced by WinTel compatible in the late 1990s. Modern machines can still run Win32 and applications written for Win32, and thus are WinTel compatible.

Of course, being WinTel compatible matters less than ever before. Much of the software people care about is now either browser-based or open source and compiled for multiple targets. We also now have dynamic recompilers that are quite good, and therefore even being compiled for the target is... well, not as important.

We need some new kind of standard that identifies general purpose, superscalar CPU with large cache and SIMD, a PCIe controller with many lanes, a memory controller for DDR4/5 paired with UEFI and either a modern GPU or a decent NPU (or both). Currently, this describes a few RISC-V machines, many ARM machines, and most AMD64 machines after about 2018. Maybe this is something like 5th Generation Industry Standard Architecture or 5SA? Whatever the industry does or doesn't call it, it's certainly not PC compatible in any sense.