|Location||QXL (SMSQ only)|
This is an undocumented command and it is uncertain what its parameters do - it affects the rate at which the screen is updated on the QXL. The higher x and y, the faster that the screen is updated (and hence the smoother the graphics), although this also slows down the other parts of the QXL. If x and y are equal to 0, the screen is only updated when you press a key - this allows the QXL to perform complex maths routines very quickly (so long as they do not access the screen).
Prior to SMSQ/E v2.65 if you used DISP_UPDATE with a parameter larger than 1 in MODE 8, this could cause problems on screen.
Using parameters smaller than 0 could lock up some versions of QXL. SCR_PRIORITY is similar under Amiga QDOS.