Comparison Between the CRX-48Z/HCRX-24Z and the HP VISUALIZE-48/HP VISUALIZE-48XP

HP Visualize-48 and HP Visualize-48XP use the hphcrx48z device driver instead of the hpcrx48z and hphcrx device drivers used by the CRX-48Z and HCRX-24Z graphics devices.

The HP Visualize-48 and HP Visualize-48XP are highly compatible with the CRX-48Z and HCRX-24Z graphics devices. This allows applications written and delivered for the CRX-48Z and HCRX-24Z to use the HP Visualize-48 and HP Visualize-48XP accelerators without requiring different executable code.

The gescapes available for the CRX-48Z and HCRX-24Z are supported by the HP Visualize-48 and HP Visualize-48XP.

Possible behavioral differences between the CRX-48Z and HCRX-24Z and the HP Visualize-48 and HP Visualize-48XP are mostly because of hardware differences. These behavioral differences should not affect the operation of the application and may only be observed when directly comparing the images between the accelerated and unaccelerated driver. Some of these differences are discussed below.

Backing Store

Backing store is an X11 feature that allocates main memory for obscured regions of a window. Graphics operations are written to this memory as well as the screen. When the window is unobscured, the screen is updated from this memory. This feature is not supported by the HP Visualize-48, HP Visualize-48XP, CRX-48Z, and HCRX-24Z, unless rendering to the overlay planes. Therefore, applications in the X environment should capture and act on expose events and redraw the image when one is received. X events are documented in the Programming with Xlib manual.

	NOTE: Support for both backing store and save under may change in future releases of the Starbase graphics library.

Image Differences

Because of the different mechanisms used to generate the image when using the HP Visualize-48 and HP Visualize-48XP accelerators, there may be minor visual differences between accelerated and unaccelerated images. These minor differences are listed below.

• Different visibility properties - very small primitives may be invisible, that is, where the rendering starts and stops on the same pixel, such as the dot on the letter i. If every pixel is required, see the DRAW_POINTS gescape.

• Slight shifts in the image location on the display.

• Minor differences in color interpolation.

• Minor differences in pattern alignment or line type segment alignment.

	NOTE: These differences should be minor. They may change in future releases of the Starbase graphics library.