What is Dynamic Video Memory Technology (DVMT)?
DVMT is a concept used in the Intel® 82915G/82910GL Express Chipset family and the Mobile Intel® 915GM/GMS, 910GML Express Chipset family wherein the optimum amount of memory is dynamically allocated and de-allocated as needed for balanced 2D/3D graphics and system performance. DVMT allocates the proper amount of display, texturing, and buffer memory after the operating system has booted. The operating system views the Intel® Graphics Media Accelerator Driver as an application, which uses Intel® Direct AGP to request allocation of additional memory for 3D applications, and returns the memory to the operating system when no longer required.
What are the benefits of DVMT?
DVMT ensures the most efficient use of available system memory resources for maximum 2D/3D graphics performance.
DVMT aligns with Microsoft's* "good driver" design guidelines as it dynamically uses only as much system memory as is needed and returns these resources to the operating system when finished. Memory is wasted in some integrated graphics solutions as large amounts of memory are permanently allocated for dedicated use.
What is pre-allocated memory?
Pre-allocated memory is the small amount of system memory made available at boot time by the system BIOS for video. Pre-allocated memory is also known as locked memory. This is because it is "locked" for video use only and as such, is invisible and unable to be used by the operating system. The Intel 82915G/82910GL Express Chipset family and the Mobile Intel® 915GM/GMS, 910GML Express Chipset family allows pre-allocated memory in the system BIOS to be set to either 1 MB or 8 MB. Upon boot, the System BIOS will pre-allocate the amount selected (1 MB or 8 MB) from the top of the main system memory, which will be dedicated for VGA/SVGA graphics.
Who sets pre-allocated memory?
The amount of pre-allocated memory is set by the system manufacturer via the system BIOS. Depending on the system BIOS implementation, this amount may or may not be configurable by the end user.
How does one determine/choose pre-allocated memory size?
512K setting: This choice is provided as a legacy setting only and should not be used.
1 MB setting: This choice allows most memory resources to go to the operating system while allowing the BIOS for all modes.
8 MB setting: This is the most likely choice, as this setting: 1) Allows a good balance between BIOS- and operating system-required memory resources for a typical 128 MB memory system; 2) Enables booting of Microsoft* operating systems in as much as 1600x1200x32 mode without the driver having to ask the operating system for more memory.
Both the 512K and 1 MB settings assume the system is booting using a Microsoft* operating system.
What if an application requires more than the total amount of pre-allocated memory?
In systems using the Intel 82915G/82910GL Express Chipset family and the Mobile Intel® 915GM/GMS, 910GML Express Chipset family, if a graphics intensive application, such a game, a DVD, etc., requires more memory than the amount of video memory that has been pre-allocated, it will communicate that need to the Intel® Graphics Media Accelerator Driver. DVMT will then ask the operating system to supply the additional memory required. When the application no longer requires the extra memory, DVMT returns it to the operating system where it can once again be used as system memory.
What is the relationship between pre-allocated memory, the Intel Graphics Media Accelerator Driver, DVMT, a Microsoft* operating system, and applications?
In systems using the Intel 82915G/82910GL Express Chipset family and the Mobile Intel® 915GM/GMS, 910GML Express Chipset family, if a graphics intensive application, such a game, a DVD, etc., requires more memory than the amount of video memory that has been pre-allocated, it will communicate that need to the Intel Graphics Media Accelerator Driver. DVMT will then ask the operating system to supply the additional memory required. When the application no longer requires the extra memory, DVMT returns it to the operating system where it can once again be used as system memory.
When is DVMT triggered?
DVMT is triggered any time an application needs video memory above the amount that has been pre-allocated. It is triggered again when an application no longer requires the extra memory and the memory needs to be returned to the operating system.
DVMT may also be triggered at boot time if a screen resolution is set that requires more memory than the total amount set as pre-allocated memory.
Will DVMT always get the memory requested?
DVMT may not always get the memory being requested. It is up to the operating system to decide whether the request for additional memory will be granted or not. DVMT allows the operating system to make this important decision based on availability of system memory resources and other requests it may be receiving.
How much graphics memory does DVMT use?
The term "graphics memory size" is the same as "memory size" in the Control Panel/Display Adapter pages or "video memory" used by external PCI Express* graphics cards. This is the memory that will be dedicated for graphics for the time that the application is active and the operating system has granted the requested memory.
Memory size = Pre-allocated memory + Additional memory requested by the application via the Intel Graphics Media Accelerator Driver.
The maximum amount of graphics memory will depend on the computer's System BIOS configuration. In most cases, the sum total will not exceed 128MB. On some older computers, the system BIOS does not limit the graphics memory to 128MB and so users may see maximum graphics memory up to 224MB.
Pre-allocated memory is invisible to the operating system. The additional memory requested by the application is relinquished back to the operating system upon exit by the Intel Graphics Media Accelerator Driver.
This applies to: