AMD Introduces New Dynamic Local Mode Balancing
Samuel Wan / 2 years ago
AMD Makes Dynamic and Local Modes Switch Seamless
As a result of Threadripper, users now have access to an unprecedented number of cores. Due to the complexities of large core designs, AMD made some compromises with the design. Each Threadripper 2 CPU contains 4 dies with 8 cores each. Due to design constraints to fit so many cores on one chip, sacrifices have to be made. To combat the issue, AMD is releasing a new Dynamic Local Mode for memory access.
When AMD created Threadripper 2, the design featured 4 dies and 4 memory channels. Due to the shared platform with EPYC which has 8 channels, a limitation arose where only 2 Threadripper dies could have memory access. This created problems with latency for the dies without direct memory access. To balance the issue, AMD used Local and Dynamic Mode. Local mode restricts memory usage for active cores to closest memory first, cutting latency at the cost of bandwidth. Dynamic mode allows the core to use the whole bank of memory, using all 4 channels at the cost of latency.
Dynamic Local Mode Balances Application Specific Latency and Bandwidth
The problem when it came to using the modes is that it required a restart. This is where Dynamic Local Mode comes in. The new service runs in the background to identity is an application is more latency or bandwidth sensitive. Depending on its need, the application will then be assigned to either close memory for low latency or all memory for bandwidth. This should help balance workloads between gaming (latency) and content creation (bandwidth) for instance. It also allows mixed workloads to run together at the same time with less conflict than the arbitrary Dynamic or Local options as before.
For now, the new service is only available for the top end Threadripper 2990WX and 2970WX CPUs. These chips have the most to contend with as they use all 4 dies actively. For the rest of Threadripper 2, they only use 2 of the dies so they fare a bit better. Perhaps AMD will implement Dynamic Local Mode for them in the future as well. With up to 49% gains in performance in a best-case scenario, it is well worth the effort. Finally, the new feature will be backwards compatible with X399 motherboards.