Integrated Graphics Subsystem

6.2.1 Video Memory Allocation Reporting

The IGC does not have local memory at its disposal but instead uses a portion of system memory allocated for frame buffering and texturing. 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.

Example: A system with 128 MB of SDRAM with the video BIOS set to 8 MB will be reported by MS Windows as having 120 MB.

The IGC 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 IGC Extreme Graphics drivers, the pre-allocated memory will then be re-claimed by the drivers and may or may not be used by the IGC in the “extended” graphic modes. However, it is important to note that pre-allocated memory is available only to the IGC, not to the OS.

The 915G's DVMT function is an enhancement over the Unified Memory Architecture (UMA) of earlier copyists. The DVMT of the 915G selects, during the boot process, the maximum graphics memory allocation possible according on the amount of system memory installed:

SDRAM Installed

Maximum Memory Allocation

128 to 256 megabytes

8-32 MB

257 to 511 megabytes

8-64 MB

 

 

> 512megabytes

8-128 MB

The actual amount of system memory used by the IGC (in the “extended” or “extreme” modes) will increase and decrease dynamically according to the needs of the graphics 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 2000 or XP, go to Display Properties > Settings> 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 (Windows 98 will typically show 0.5 to 5 MB or higher, depending on screen resolution and application. In Windows 2000 or XP, the video memory size reported by DirectX will always be 32 MB, even if the total memory installed is over 128 MB.

✎Some applications, particularly games that require advanced 3D hardware acceleration, may not install or run correectly on systems using the IGC.

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Technical Reference Guide