I _think_ that, if either of those values report non-zero, we'd also need to have subfunction 5B implemented. I'm not sure either where those alternate registers are located (I suspect it's internal to each implementation, though I'm admittedly getting out of my depth on that one), but 5B provides …

Below are details of the various fields from the LIM EMS spec and also some notes on alternate register sets. I know you didn't ask about the latter, but it might be useful. Comparatively, when using MS-DOS 5 or 6.22 in a VirtualBox VM with EMM386, DMA_channels also reports 0 while alternate_ …

int 67, sub 52: get/set handle attributes int 67, sub 59: get hardware configuration A couple simple functions filled out to help with detection of EMS details. It is unclear if there is any specific game out there that depends on them, but they are definitely used (and complained about) by …