CONVERTING A PROGRAM FROM REAL TO PROTECTED MODE

I want to convert a real-time application which hooks into IRQ5
running at 250Hz, makes dos calls for screen output but does not access
any real mode device drivers.

Are there any catches? How do I ensure the real-time performance is not
affected (eg. by context switching?).

I have tried to run a no-real time, off-line graphics program
in real mode and the graphics (egavga.bgi) performance was awfully
slow.

Please could you post a reply back to to...@iconz.co.nz, I would
really appreciate some help. Thanks.