HP Compaq dc7900 USDT Technical Reference Manual page 73

The GMA 4500 uses a portion of system memory for instructions, textures, and frame (display)
buffering. Using a process called Dynamic Video Memory Technology (DVMT), the controller
dynamically allocates display and texture memory amounts according to the needs of the
application running on the system.
The total memory allocation is determined by the amount of system memory installed in a
system. The video BIOS pre-allocates 8 megabytes of memory during POST. System memory
that is pre-allocated is not seen by the operating system, which will report the total amount of
memory installed less the amount of pre-allocated memory.
The GMA 4500 will use, in standard VGA/SVGA modes, pre-allocated memory as a true
dedicated frame buffer. If the system boots with the OS loading the GMA Extreme Graphics
drivers, the pre-allocated memory will then be re-claimed by the drivers and may or may not be
used by the GMA in the "extended" graphic modes. However, it is important to note that
pre-allocated memory is available only to the GMA, not to the OS.
The Q45's DVMT function is an enhancement over the Unified Memory Architecture (UMA) of
earlier systems. The DVMT of the Q45 selects, during the boot process, the maximum graphics
memory allocation possible according on the amount of system memory installed:
SDRAM Installed
1 GB
> 1 GB
The actual amount of system memory used by the GMA in the "extended" or "extreme" modes
will increase and decrease dynamically according to the needs of the application. The amount of
memory used solely for graphics (video) may be reported in a message on the screen, depending
on the operating system and/or applications running on the machine.
For viewing the maximum amount of available frame buffer memory MS Windows go to the
Control Panel and select the Display icon, then > Settings > Advanced > Adapter.
The Microsoft Direct Diagnostic tool included in most versions of Windows may be used to
check the amount of video memory being used. The Display tab of the utility the "Approx. Total
Memory" label will indicate the amount of video memory. The value will vary according to OS.
✎
Some applications, particularly games that require advanced 3D hardware acceleration, may not
install or run correctly on systems using the GMA.
Technical Reference Guide
Table 6-1.
GMA 4500 Memory Allocation
Maximum Memory Allocation
256 or 512 MB
384 MB
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Integrated Graphics Subsystem
6-3