If it's a 64-bit build made using Visual Studio, you get 4.99999999999. Visual Studio doesn't support 80-bit floating point math for that target, even though x64 CPUs still support 80-bit floating point math when you use the legacy floating point instructions. Visual Studio also does not support inline assembly to let you make use of 80-bit floating point instructions.
But if you set the CPU core to "Dynamic", then you get the proper value of "5". Or if you use the MingW builds, those also support 80-bit floating point math and give the correct value of "5".
It is quite embarrassing to ship a CPU emulator with broken floating point math as the default.
I guess it makes sense to try it anyway. Now I'm wondering how I'd be able to detect something like Concurrent DOS or REAL/32 or REAL/NG.
_Even_ if you run the MS-DOS kernel in DOSBox, the builtin DOS literally leaks through in many places (e.g. many API services still available instead of crashing), with only some of the more recent forks even trying to hide it.
There's also an adversarial aspect to this. Some emulators try to avoid detection and a lot of software tries to detect if it's running under virt for various reasons, eg. to stop cheating in games or stop reverse-engineering. (virt-what is deliberately not adversarial, it's very easy to "trick" it if you wanted to do that)
Example: There is (was? I don't actively follow the community) a patch set for a particular piece of VM software that made it undetectable to anti-cheat in games.
While I don't use said software (I have a casual interest in it only...would be nice to get more games working on Linux), I have to disclose that I'm against anti-cheat mechanisms. I'm a software engineer, and I've worked on a few smaller games, and know the overall structure of bigger ones, and I don't think I've ever seen a game use good practices in multiplayer. Instead, they usually rely on client side code and lean on anti-cheat software to stop cheaters.
What's WGU in this context?
> which makes enough sense since if you're in a VM they can't see your full screen
Presumably they can't also see the screen of another device...
When taking a test they have a proctor that's watching you on a webcam, and they make you pan the webcam around the room to ensure that there's no obvious way to cheat, and they make you share your screen to ensure you only have a browser running.
It’s perfect for all parties, and doesn’t intrude on your personal living space or devices.
Well that level of intrusiveness would just make me come up with something overly complicated just so I could prove that I could cheat if I wanted.
They just want to make it difficult enough to catch most.