Thanks! I learned something new today, and that makes today a good day. I’ll strike out a few relevant parts of my answer when I get a minute to open the beast.

I mean… DX 9, 10, and 11 were all released prior to Nadella being CEO/chairman.

But in software, it’s very commonplace for library versions not to be backwards compatible without recompiling the software. This isn’t the same thing as being able to open a word doc last saved on a floppy disk in 1997 on Word 365 2024 version, this is about loading executable code. Even core libraries in Linux (like OpenSSL and ncurses) respect this same schema, and more strongly than MS.

Using OpenSSL as an example, RHEL 7 provides an interface to OpenSSL 1.0. But 1.1 is not available in the core OS, you’d have to install it separately. 1.1 was introduced to the core in RHEL 8, with a compatibility library on a separate package to support 1.0 packages that hadn’t been recompiled against 1.1 yet. In RHEL 9, the same was true of OpenSSL 3 - a compatibility library for 1.1, and 1.0 support fully dropped from core. So no matter which version you use, you still have to install the right library package. That library package will then also have to work on your version of libc - which is often reasonably wide, but it has it limits just the same.

DirectX 12 was released in 2015 with Windows 10, so it’s unlikely to have been ported back to 8.1 and lower.

MS usually only does current+ with compatibility - so for example FF11 (DirectX 8.1 I think) still works (mostly) on Windows 11, but DX12 won’t work on W7

DirectX, OpenGL, Visual C++ Redist and many other support libraries in software programs typically require the same major version of the support libraries that they were shipped with.

For DirectX, that major version is 9, 10, 11, 12. Any major library change has to be recompiled into the game by the original developer. (Or a very VERY dedicated modder with solid low level knowledge)

Same goes for OpenGL, except I think they draw the line at the second number as well - 2.0, 3.0, 4.0, 4.1, 4.2, 4.3, 4.4.

For VC++, these versions come in years - typically you’ll see 2008, 2010, 2013, and the last version 2015-2022 is special. Programs written in the 2013 version or lower only require the latest version of that year to run. For the 2015-2022 library, they didn’t change the major version spec so any program requiring 2015+ can (usually) just use the latest version installed.

The one library that does weird things to this rule is DXVK and Intel’s older DX9-on-12. These are translation shim libraries that allow the application to speak DX9 etc and translate it on the fly to the commands of a much more modern library - Vulkan in the case of DXVK or DX12 in Intel’s case.

Edited to remove a reference to 9-on-12 that I think I had backwards.

Not on a flash based motherboard (so basically almost everything recent). On modern systems usually the only thing the battery powers is the clock, which is why they have a separate reset to defaults header/button/switch.

(The CMOS memory of old is replaced with flash memory, al la SD Card or flash drive)