DVMT Mode from The Tech ARP BIOS Guide

DVMT Mode from The Tech ARP BIOS Guide

DVMT Mode

Common Options : Fixed, DVMT, Both

 

Quick Review of DVMT Mode

Unified Memory Architecture (UMA) is a concept whereby system memory is shared by both CPU and graphics processor. While this reduces cost, it also reduces the system’s performance by taking up a large portion of memory for the graphics processor.

Intel’s Dynamic Video Memory Technology (DVMT) takes that concept further by allowing the system to dynamically allocate memory resources according to the demands of the system at any point in time. The key idea in DVMT is to improve the efficiency of the memory allocated to either system or graphics processor.

The BIOS feature that controls all this is the DVMT Mode BIOS feature. It allows you to select the DVMT operating mode.

When set to Fixed, the graphics driver will reserve a fixed portion of the system memory as graphics memory. This ensures that the graphics processor has a guaranteed amount of graphics memory but the downside is once allocated, this memory cannot be used by the operating system even when it is not in use.

When set to DVMT, the graphics chip will dynamically allocate system memory as graphics memory, according to system and graphics requirements. The system memory is allocated as graphics memory when graphics-intensive applications are running but when the need for graphics memory drops, the allocated graphics memory can be released to the operating system for other uses.

When set to Both, the graphics driver will allocate a fixed amount of memory as dedicated graphics memory, as well as allow more system memory to be dynamically allocated between the graphics processor and the operating system.

It is recommended that you set this BIOS feature to DVMT for maximum performance. Setting it to DVMT ensures that system memory is dynamically allocated for optimal balance between graphics and system performance.

 

Details of DVMT Mode

Unified Memory Architecture (UMA) is a concept whereby system memory is shared by both CPU and graphics processor. While this reduces cost, it also reduces the system’s performance by taking up a large portion of memory for the graphics processor.

Intel’s Dynamic Video Memory Technology (DVMT) takes that concept further by allowing the system to dynamically allocate memory resources according to the demands of the system at any point in time. The key idea in DVMT is to improve the efficiency of the memory allocated to either system or graphics processor.

To ensure better allocation of system memory, DVMT comes with three different operating modes :

  • Fixed Memory
  • DVMT Memory
  • Fixed + DVMT Memory

But before we go into the details of each mode, it’s important to note that the system boots up with some system memory pre-allocated for graphics, irrespective of the DVMT operating mode. Depending on the motherboard manufacturer, you may or may not be allowed to select between a choice of 1MB or 8MB of pre-allocated memory.

This pre-allocated memory is dedicated to VGA/SVGA graphics and will be treated by the operating system as dedicated graphics memory. This pre-allocated memory will not be visible or accessible to the operating system. It will be used during the booting process to display the boot and splash screens, or when you run MS-DOS games and applications. It will also be used when Windows XP loads in Safe Mode.

Once an operating system with the appropriate Intel Graphics Media Accelerator Driver loads up, the graphics processor reclaims the pre-allocated memory for its use. But again, it is only available for use as graphics memory. It will never be made available to the operating system or applications. The Intel GMA driver then loads additional system memory according to the DVMT operating mode.

The Fixed Memory operating mode reserves a fixed amount of system memory as graphics memory. This is in addition to the memory already pre-allocated. Like pre-allocated memory, this fixed amount is no longer available to the operating system. But when the operating system reports the total system memory, it will include this amount, as opposed to pre-allocated memory.

The DVMT Memory operating mode allows the graphics driver to dynamically allocate system memory for use by the graphics processor. When no graphics-intensive operations are occuring, most of the DVMT memory can be reallocated to the operating system for other uses. When more graphics memory is required, the graphics driver will automatically reallocate more system memory for use as graphics memory.

The Fixed + DVMT Memory operating mode is an combination of the Fixed and DVMT operating modes. It allows you to allocate a fixed amount of reserved graphics memory (over the minimum pre-allocated amount), as well as a portion of system memory that can be dynamically allocated to both graphics processor and operating system.

This figure from Intel clearly shows the differences between the three different DVMT operating modes :

Intel DVMT Modes

The BIOS feature that controls all this is the DVMT Mode BIOS feature. It allows you to select the DVMT operating mode.

When set to Fixed, the graphics driver will reserve a fixed portion of the system memory as graphics memory. This ensures that the graphics processor has a guaranteed amount of graphics memory.

But the downside is, once allocated, this memory cannot be used by the operating system even when it is not in use. Usually, the following configuration scheme is used :

System Memory DVMT Graphics Memory
Pre-Allocated Fixed Total
128 – 255 MB 1 MB 31 MB 32 MB
8 MB 24 MB
256 – 511 MB 1 MB 63 MB 64 MB
8 MB 56 MB
1 MB 127 MB 128 MB
8 MB 120 MB
512 MB and larger 1 MB 63 MB 64 MB
8 MB 56 MB
1 MB 127 MB 128 MB
8 MB 120 MB

When set to DVMT, the graphics chip will dynamically allocate system memory as graphics memory, according to system and graphics requirements. The system memory is allocated as graphics memory when graphics-intensive applications are running.

But when the need for graphics memory drops, the allocated graphics memory can be released to the operating system for other uses. Usually, the following configuration scheme is used :

System Memory DVMT Graphics Memory
Pre-Allocated Fixed Total
128 – 255 MB 1 MB 31 MB 32 MB
8 MB 24 MB
256 – 511 MB 1 MB 63 MB 64 MB
8 MB 56 MB
1 MB 127 MB 128 MB
8 MB 120 MB
1 MB 159 MB 160 MB
8 MB 152 MB
512 MB and larger 1 MB 63 MB 64 MB
8 MB 56 MB
1 MB 127 MB 128 MB
8 MB 120 MB
1 MB 223 MB 224 MB
8 MB 216 MB

When set to Both, the graphics driver will allocate a fixed amount of memory as dedicated graphics memory, as well as allow more system memory to be dynamically allocated between the graphics processor and the operating system. Usually, the following configuration scheme is used :

System Memory DVMT Graphics Memory
Pre-Allocated Fixed Total
128 – 255 MB NA
256 and larger 1 MB 63 MB + 64 MB 128 MB
8 MB 56 MB + 64 MB

It is recommended that you set this BIOS feature to DVMT for maximum performance. Setting it to DVMT ensures that system memory is dynamically allocated for optimal balance between graphics and system performance.

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