Given that Quake 2 already runs on Windows 95 back in the days, and how Windows 95 is already somewhat of an "exokernel" to DOS, I wonder how hard it is to port to DOS, actually? Well, given that you can have almost full control to the hardware and framebuffer, and memory allocation and how you can directly issue BIOS calls...I guess the performance should be prettier right?
I don’t think you could fairly say Windows 95 is an exokernel to DOS. Windows 95 is a whole OS, which happened to go through DOS during the boot process, and keep bits of DOS around for certain pieces of functionality (device drivers?)
Maybe Quake II on DOS will run with less system memory than the Windows version.
Windows 95, like Windows 3.x enhanced mode and Windows/386 before that, is actually a hypervisor that runs DOS in VMs; and one of those VMs, the "system VM", runs a DOS extender that handles the Win32 and GUI part.
Notably, the DOS environment under Windows is running in a hardware mode called "virtual 8086 mode" which allows it to be isolated from the other DOS environments and, even more importantly, from full BIOS access. These limitations kept the whole system safer and more stable than DOS in "real mode" but made some DOS programs unusable under Windows.
Windows 95 had a horrible reputation for games in the early days, for good reasons or not (maybe mostly because how bad Windows 3.x was for games?). Quake was possibly the first mainstream game that managed to convince many that it was possible to get good games performance without sticking to MS-DOS? 1997 was still a great year for DOS games really. Even 1998 was not bad. For someone playing games on a PC in that era there was really no hurry to switch to Windows 95/98 (but by 1997 I had moved on to Linux instead anyway).
Windows 95 is so good at pretending to not be there that it convinced a generation of nerds that it was a thin layer on top of DOS, but the reality is the other way round.
