Direct Memory Access (DMA) Coalescing

DMA (Direct Memory Access) allows the network device to move packet data directly to the system’s memory, reducing CPU utilization. However, the frequency and random intervals at which packets arrive do not allow the system to enter a lower power state. DMA Coalescing allows the Ethernet device to collect packets before it initiates a DMA event. This may increase network latency but also increases the chances that the system will consume less energy.

Higher DMA Coalescing values result in more energy saved but may increase your system’s network latency. If you enable DMA Coalescing, you should also set the Interrupt Moderation Rate to Minimal. This minimizes the latency impact imposed by DMA Coalescing and results in better peak network throughput performance.

You must enable DMA Coalescing on all active ports in the system. You may not gain any energy savings if it is enabled only on some of the ports in your system. There are also several BIOS, platform, and application settings that will affect your potential energy savings. A white paper containing information on how to best configure your platform is available on the Intel website.

To change this setting in Intel® PROSet:

This setting is found on the Advanced tab of the device’s Device Manager property sheet or in the Adapter Settings panel in Intel® PROSet Adapter Configuration Utility (Intel® PROSet ACU).

To change this setting in Windows PowerShell*, use the Set-IntelNetAdapterSetting cmdlet. For example:

Set-IntelNetAdapterSetting -Name "<adapter_name>" -DisplayName "DMA Coalescing"
-DisplayValue "Enabled"