Video Memory Module (Vmm) - Compaq PowerStorm 1000 Owner's Manual

Technical Description

6.3.6 Video Memory Module (VMM)

One Video Memory Module is required if two Image Rendering Modules are in the
PowerStorm 1000 graphics subsystem, two if there are four Image Rendering Modules.
Each Video Memory Module contains a Raster Controller (RC) ASIC and VRAM screen
buffer memory for resolutions of up to 2048 x 1024 containing:
•
Eight bits double-buffered red data
•
Eight bits double-buffered green data
•
Eight bits double-buffered blue data
•
Eight bits window identification information
•
Eight bits double-buffered overlay information
The RC ASIC manages the random access port of the VRAM, storing pixels assembled by
the SAM ASICs in the Image Rendering Module. The serial port is forwarded to the
Standard Resolution Module or the High Resolution Module with the Window ID (WID)
clocked out several cycles ahead to allow time for the buffer selection information to
propagate back from the Window Attribute Mixer (WAM) ASIC. A block diagram of the
interface to the Video Memory Module is shown in Figure 6-3. A block diagram of a
single pixel is shown in Figure 6-4.
6–8 DIGITAL PowerStorm 1000 Graphics Subsystem Owner's Guide