[privatelypublic]

Define "486-compatible." As far as I know even intel's newest cpus can run 486 era 16-bit stuff in hardware.

But, a plain answer: Via Eden boards. still use north/southbridge architecture, and are from the mid 2000's.

It's just modern Windows/Linux that have discontinued the ability. Or, perhaps you have 16/32 and 32/64 and are unable to do 16bit on 64bit machines- which still boils down to "operating system."

By far the biggest issue though is that even the Via Eden processor is significantly faster than a 486- and lots of software (especially games) from that era used no-op instruction loops for timing and timers. This results in games like The Incredible Machine's level timer running out in half a second or less.

[p_ing]

In Windows, once you're in long mode, there's no 16-bit available to you. You can instead take the DOSBox or other VM route.

Linux isn't really relevant given the time frame.

[privatelypublic]

I left it open as to if it was a hardware or OS level item that prevents 16bit. Because I don't know, and don't care to dig that rabbit hole.

Also- DOSBox is an emulator vs VMs are hardware, no? I suspect A VM won't fix the "no-op loop for timing" issue- with modern processors' lowest clock being 600-800Mhz before it gets C6/C7'd, 30 years of IPC improvement, and the possibility of the CPU itself optimizing such loops (I'm unsure for various reasons): I expect the UX of "just limit how many scheduler slices it gets" to be nasty.

[p_ing]

DOSBox is an emulator.

https://en.wikipedia.org/wiki/DOSBox#Hardware_emulation