Zen 3 user reports intermittent zero generation
1 Sep 22 6:24 AM · 1d ago · 1 article · 1 post · 3 comments · 2 sources · development 1 of 4
A user on Zen 3 reports being able to generate 16-bit zeros, suggesting the bug may have been fixed after Zen 2.
“I'm getting 16-bit zeros on my Zen 3 chip (+1:3821, 0:3893, -1:3895), I will wait to get some statistically significant samples for the 32-bit values and update the forum thread. Maybe it was fixed after Zen 2?”
matjajstanley Zen 2 CPU owner, bug reproducer0x000xca0xfe Hardware/cryptography developerAMD CPU manufacturer
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Reported in the same hours no headline names this development itself — these 1 claim were published in its stretch
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first by HN Best, 1d ago · also HN Frontpage
What people said 3 voices · verbatim
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This is not the first RNG bug on Zen 2, I recall after I first got mine that some application or other would quit immediately at startup because rdrand always returned -1, i.e. all 1s. It was fixed with a microcode update.Do we now learn that they fixed "always generate all 1s" with "never generate all 0s"??EDIT: I've been unable to reproduce the…
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I'm getting 16-bit zeros on my Zen 3 chip (+1:3821, 0:3893, -1:3895), I will wait to get some statistically significant samples for the 32-bit values and update the forum thread. Maybe it was fixed after Zen 2?
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Embarrassing, but probably little practical impact, since these hardware random numbers are typically not used directly and instead seed a CSPRNG.
All 4 developments of AMD's RDRAND16 instruction can't generate zero on some Zen… →
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