I now that when in p-mode you can switch to real-mode run an interrupt then jump back into p-mode.

I know this is underhanded, but easier than all the *fun* programming with the dma, pci, ect.

But does this switching, which may happen many times a second, put any undue stress on the CPU. I don't want to shorten my cpus life-span just for a neat shortcut

Thanks

No.

It's no differant than running any other code and it may not be as slow as some people think.
For my OS i written a pmode floppy driver, this worked great, but would not let me load from a USB pen drives, as i already had a function to go back and forth to real mode, i converted it to do int 13h for floppy functions, i thought it would be slow, but OK to load stuff from usb etc.
To keep it simple it loads 512bytes in realmode switch to pmode loads the 512bytes to buffer and keeps switching until is loaded the file etc.
But when i tested it, to my supprize it faster than a windows floppy driver .