Tie Fighter (DOS) intentionally employs inverted mouse movement along the y-axis. Attached a dosbox patch to reverse this mouse movement (so that mouse forward moves cursor upwards, like a typical FPS game). The y-axis orientation is toggled by pressing CTRL-ScrollLock. Also, it is required to load the ctmouse.exe driver before starting Tie Fighter. An added advantage of this driver is that mouse motion is accelerated, which better simulates joystick motion, and allows for easier navigation in-game.

It may also be necessary to increase mouse sensitivity in dosbox by editing the dosbox configuration file (dosbox.conf) and increase the sensitivity above 100, like so:
sensitivity=250

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An alternative mouse driver with higher mouse acceleration is the "Microsoft Mousedriver V7.04 for DOS". If choosing this option instead of ctmouse, then first run mouseoff inside dosbox and then run the MS Mousedriver 7.04 like so: mouse.com /P1 /S100

It may also be necessary to increase the dosbox mouse sensitivity to 250 or thereabouts.
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Note that mouse movement is a complex function in dosbox, so this patch should only be used where applicable.