Inquiry on Intel TCC & RDT (CAT) Compatibility and Full-Stack Hardware Support

[xujiqian]

Hi there,

I am currently exploring real-time performance optimization on Intel platforms. However, I have encountered some ambiguities regarding the coexistence of TCC (Time Coordinated Computing) and RDT (Resource Director Technology, specifically CAT). I would appreciate some clarification on the following points:

1. Compatibility Conflict between TCC and RDT

• I noticed conflicting information between the official documentation and reference implementations:

• The Intel ECI Documentation states that TCC and RDT do not coexist well at this stage and recommends disabling TCC when RDT is needed.

• However, the Edge Developer Kit reference scripts demonstrate a setup where both TCC and CAT (RDT) are utilized simultaneously for real-time optimization.

Question: Can TCC and RDT (CAT) be enabled and used concurrently in the current software stack? If there are still limitations, what is the root cause of the conflict?

2. Hardware and Chipset Support Requirements

Regarding the hardware prerequisites for these features:

• Is "Full Stack" support (CPU, Chipset, and BIOS/Firmware) strictly required to enable both TCC and RDT?

• While CPU support is well-documented, chipset-level support is less clear. Do industrial chipsets such as H610E, Q670E, and R680E fully support both TCC and RDT?

• Can we assume that all models listed in the ECI Validated Hardware Platforms and the Edge Developer Kit reference list have been verified to support TCC and RDT working together?

Thank you for your time and help!

[syazaath]

Hi @xujiqian, thank you for your question.

Q1: Can TCC and RDT (CAT) be enabled and used concurrently in the current software stack? If there are still limitations, what is the root cause of the conflict?
A1: The official Intel ECI documentation is correct in stating that, as of the current software and hardware stack, TCC and RDT (CAT) do not always coexist seamlessly. The recommendation to disable TCC when RDT is needed is based on known limitations and potential conflicts in resource management and cache allocation.
However, some reference implementations (such as the Edge Developer Kit scripts) may demonstrate both features enabled for specific real-time optimization scenarios. These are typically controlled, validated configurations and may not represent the general case or all possible workloads.
Yes, there are still limitations. The root causes are:

Static vs. Dynamic Resource Allocation:

RDT/CAT partitions the LLC into ways assigned to different CLOS values. This partitioning is static—if a CLOS is assigned 25% of the cache, it cannot use more, even if the rest is idle.
TCC, on the other hand, requires deterministic, low-latency access to memory and cache resources, often expecting dynamic, work-conserving behavior to guarantee real-time deadlines.

Potential for Resource Starvation or Priority Inversion:

If both TCC and RDT are enabled, TCC workloads may be artificially limited by CAT’s static partitioning, leading to missed deadlines or degraded real-time performance.
Conversely, disabling CAT allows TCC to use the full cache, but then you lose the isolation and QoS guarantees that RDT provides for other workloads.
Software Stack and Validation:

The current software stack and validation coverage may not guarantee correct operation or optimal performance when both features are enabled together, especially for general-purpose or mixed-criticality systems.

Q2: Can we assume that all models listed in the ECI Validated Hardware Platforms and the Edge Developer Kit reference list have been verified to support TCC and RDT working together?

A2: This list here https://eci.intel.com/docs/3.3/getstarted/requirements.html#validated-hardware-platforms means the ECI has validated such item for the components that was intact with ECI.

This list https://github.com/open-edge-platform/edge-developer-kit-reference-scripts/tree/d67845df7244872a786b73cd888368ef9a1ea151?tab=readme-ov-file#validated-hardware--configurations is validated hardware configs for devkit scripts, which is the baseline of the usecase. For a specific usecase like realtime, the validated hardware is https://github.com/open-edge-platform/edge-developer-kit-reference-scripts/tree/d67845df7244872a786b73cd888368ef9a1ea151/usecases/real-time/tcc_tutorial#validated-hardware/ .

Q3: Do industrial chipsets such as H610E, Q670E, and R680E fully support both TCC and RDT?

You can refer here for TCC and RDT (CAT ) https://www.intel.com/content/www/us/en/ark/featurefilter.html?productType=873&0_TimeCoordinatedComputing=True