Functional Blocks
8
VGA CONTROLLER
The zPM11 is based on the Cirrus Logic 5446 VGA controller. This controller is a highly integrated
64-bit GUI engine that has been optimized for handling graphic-intensive environments such as
Windows and OS2. The controller uses a 64-bit data path to the video memory, allowing it to surpass
many VRAM based controllers in performance. In addition, the 5446 contains several other
performance enhancers such as a BitBLT accelerator, linear addressing, hardware cursor, color
expansion, and memory mapped I/O.
The 5446 is hardware register compatible with the IBM VGA standard and can support resolutions up
to 1600 x 1200. The 5446 contains an integrated 24-bit RAMDAC, allowing the display of 16.8 million
colors.
VIDEO MEMORY
The zPM11 can be ordered with up to 4 Mbytes of high speed fast page mode EDO DRAM, allowing
it to support high resolution color graphics modes such as 1280 x 1024 x 64K colors. The memory is
organized as eight 256K x 16-bit DRAMs. The Cirrus Logic 5446 controls accesses to the display
memory and arbitrates between the display refresh requirements and CPU accesses. The address
space occupied by the video memory depends on the video mode selected. The "Display Memory
Address Map" table summarizes the address space for various video modes.
In order to allow for all possible modes of operation, memory address space from A0000 to C7FFFh
should be reserved for the display memory and video BIOS. If certain video modes, such as
monochrome text, are not used, it is possible to use the memory address space corresponding to the
unused mode.
The Cirrus Logic drivers for Windows (supplied on the Drivers and Utilities diskettes) use linear
addressing to increase performance. Linear addressing allows the controller to see a contiguous area
of memory instead of 64K pages as with the standard VGA implementation. The zPM11's linear
addressing region is mapped by the PCI BIOS as a 16Mbyte block in upper memory.
Appendix B contains specifications on the various video modes supported by the 5446 and the
memory requirements for each mode.
Display Memory Address Map
MEMORY MAP
A0000-
B0000-
B8000-
Upper Memory
Video Mode
AFFFFh
B7FFFh
BFFFFh
16Mbyte
Color Text Modes
-
-
X
-
Mono Text Modes
-
X
-
-
VGA Graphics
X
-
-
-
Extended VGA Graphics
X
X
X
X
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
