VsetScreen() can change the base addresses of both PhysicalScreen and LogicalScreen, and also can change current video mode — i.e. size and color depth of the current screen.

5 (0x05)

VsetScreen() is available on systems that have a _VDO cookie with a value of 0x00030000 or greater. This is the case as of TOS 4.00. On other systems, Setscreen() is available and should be used instead — which by the way is the same as using Vsetscreen() with mode values other than the SCR_MODECODE (3) value.

log is the new address at which the LogicalScreen buffer will start.
phys is the new address at which the PhysicalScreen buffer will start.
If either log or phys is NULL, the XBIOS will allocate a new block of memory large enough for the current screen and reset the parameter accordingly. Be warned that only one buffer is allocated at once. In other words, if both log and phys are NULL, then only one video buffer is allocated and both PhysicalScreen and LogicalScreen addresses will be set to the new allocated buffer.

mode defines the screen mode to switch to (same as Getrez()).
Setting mode to SCR_MODECODE (3) will cause modecode to be used to set the graphic mode (see VsetMode()? for valid values for this parameter), otherwise modecode is ignored.
If any of these three parameters is set to SCR_NOCHANGE (-1) then that value will be left unchanged.

	move.w	modecode,-(sp)
	move.w	mode,-(sp)
	pea	phys
	pea	log
	move.w	#$05,-(sp)
	trap	#14
	lea	14(sp),sp

Changing screen modes with this call does not reinitialize the AES.
Under genuine TOS system, the VDI and VT52? emulator are, however, correctly reinitialized, but under NVDI? it looks like the VDI is not. This leads to the necessity under NVDI? to hide the mouse (see v_rmcur()?) before switching to a new video mode, and show it again (see v_dspcur()?) after switching back to the former mode.
The AES should not be used after changing screen mode with this call until the former mode is restored.

TOS 1.00 to 1.04 required that their PhysicalScreen buffer be on a 256 byte boundary. The Falcon030? Videl chip (_VDO cookie of 0x00030000) requires a LONG boundary. All other Atari computers only require a WORD boundary.
When switching to a new video mode with the screen reallocation feature, care should be taken that enough free memory is available for the system to allocate the new video buffer.
This call is actually a revised binding of Setscreen() developed to allow access to the newly available modecode parameter.

Setscreen(), VsetMode()?