HP c8000 manual Shared memory extension Mitshm, Power saving states defined by Vesa

configuring X Windows on HP-UX (HP Visualize graphics cards)

X Server configuration

The following table is a description of the states that are defined by VESA. The Power Savings column indicates (roughly) the level of power savings achieved in the given state. The Recovery Time is the amount of time that the screen takes to return to a usable state when the screen saver is turned off (by pressing a key or the moving the mouse).

Table 2-1		Power saving states defined by VESA
	Level		State	DPMS Compliance	Power	Recovery Time
				Requirements	Savings
	0		Screen Saver	Not Applicable	None	Very Short (<1sec.)
	1		Stand-by	Optional	Minimal	Short
	2		Suspend	Mandatory	Substantial	Longer
	3		Off	Mandatory	Maximum	System Dependent

The actual amount of power saved and the recovery time for each of the states is monitor-dependent and may vary widely. The customer can compensate for this by choosing an appropriate level for the monitor that is currently in use.

By default, the DPMS level used is the Screen Saver (i.e. no power savings). If you wish to use power saving during screen blanking, set the following X*screens file entry before starting the server:

MinimumMonitorPowerSaveLevel <level>

where level is replaced with the single digit 0, 1, 2, or 3 as specified in the Level column in the above table.

shared memory extension (MIT_SHM)

The MIT shared memory extension provides both shared-memory XImages and shared-memory pixmaps based on the SYSV shared memory primitives.

Shared memory XImages are essentially a version of the XImage interface where the actual image data is stored in a shared memory segment, and thus need not be moved through the Xlib interprocess communication channel. For large images, use of this facility can result in increased performance.

Shared memory pixmaps are a similar concept implemented for the pixmap interface. Shared memory pixmaps are two-dimensional arrays of pixels in a format specified by the X Server, where the pixmap data is

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