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RDSEED

Architecture referenceFeex

RDSEED supplies values intended for seeding software random-number generators from the processor's seed-generation facility. It is separately enumerated from RDRAND and can report temporary unavailability.

What you need to know

RDSEED supplies values intended for seeding software random-number generators from the processor's seed-generation facility. It is separately enumerated from RDRAND and can report temporary unavailability.

How it works

The instruction communicates success through the carry flag. Seed availability and the documented entropy-source construction differ from the RDRAND interface. Software must handle an unavailable result and must not treat the destination register as a valid seed when the instruction reports failure.

Where it is useful

A maintained runtime can use RDSEED as one component of generator initialization under an explicit entropy policy. An application normally delegates this to the OS or cryptographic library rather than building its own entropy collection and retry loop.

How to check support and enablement

CPUID.07H.00H:EBX bit 18 enumerates RDSEED. Check success on every instruction execution and follow a bounded, documented failure strategy in the component responsible for randomness.

Use a maintained cryptographic implementation that handles feature selection, failure conditions and the complete algorithm. Hardware acceleration supplies primitives; key management, authentication, nonce rules and protocol choices remain software responsibilities.

What the feature does not establish

RDSEED is not a promise of a fixed number of successful results per second, a substitute for authentication or an automatic guarantee that a custom random generator is secure. RDRAND availability alone does not establish RDSEED.

Compatibility and performance in practice

A feature field is not a product certification or evidence that a particular application is secure. Performance depends on message sizes, mode, batching and the rest of the protocol. Check the actual provider and keep its security updates current.

A practical verification checklist

  1. Record the exact processor or platform model and the application, OS and runtime versions involved. Preserve the wording of the actual error or requirement.
  2. Check the manufacturer reference for that exact model, then inspect the effective capability and enabled state in the environment where the program runs.
  3. Compare every requirement of the selected binary or backend. A similarly named feature, alias or broad technology label is not enough.
  4. Confirm the application selected the intended implementation. Use its documented diagnostics and a supported fallback when requirements are not met.
  5. Make one supported change at a time and repeat the same workload. Keep the original configuration and recovery path available.

If the feature is listed but software cannot use it

Start with the exact failing component. A hardware database describes recorded capability; the operating system or hypervisor can expose a different effective environment. An illegal-instruction error also needs investigation of the actual faulting instruction and binary build, because corruption or an unrelated unsupported instruction can produce a similar symptom.

Install the application, driver or runtime version supported for the exact platform, and use the vendor's documented baseline or fallback build if needed. A software update cannot create an instruction that the processor lacks. Firmware and security-policy changes should follow the system manufacturer's procedure and a recovery plan rather than a generic optimization recipe.

Sources and scope of this explanation

Intel 64 and IA-32 Architectures Software Developer's Manual

These references establish architectural behavior and software requirements. They do not independently verify every feature value on a linked hardware model page. For model support, use that page's manufacturer evidence and check the effective system configuration. This article does not supply a benchmark, certification or independent review date.

Sources and verification

Editorial ownership: Feex. No independent review date is recorded. How we research.

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