From d3e566da61ec2b9aa085253bb478295113a853b3 Mon Sep 17 00:00:00 2001 From: Jeffrey Walton Date: Tue, 14 Jun 2016 22:14:35 -0400 Subject: [PATCH] Update comments for Intel RDRAND circuit and underflow --- rdrand.h | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/rdrand.h b/rdrand.h index 2729ed7f..d5798643 100644 --- a/rdrand.h +++ b/rdrand.h @@ -42,10 +42,13 @@ public: //! \param retries the number of retries for failed calls to the hardware //! \details RDRAND() constructs a generator with a maximum number of retires //! for failed generation attempts. - //! \details Empirical testing under a 6th generaton i7 (6200U) shows RDSEED fails - //! to fulfill requests at about 6 to 8 times the rate of RDRAND. The default - //! retries reflects the difference. - RDRAND(unsigned int retries = 12) : m_retries(retries) {} + //! \details According to DJ of Intel, the Intel RDRAND circuit does not underflow. + //! If it did hypothetically underflow, then it would return 0 for the random value. + //! Its not clear what AMD's behavior will be, and what the returned value will be if + //! underflow occurs. + //! Also see RDRAND + //! not really random with Oracle Studio 12.3 + patches + RDRAND(unsigned int retries = 4) : m_retries(retries) {} virtual ~RDRAND() {}