Another round of speculative-execution vulnerabilities [LWN.net]

Another round of speculative-execution vulnerabilities

Posted Aug 23, 2023 11:34 UTC (Wed) by malmedal (subscriber, #56172)
In reply to: Another round of speculative-execution vulnerabilities by JosephBao91
Parent article: Another round of speculative-execution vulnerabilities

Do you have a reference for this? I haven't read the actual specs myself, but all the articles I've read say 5.0 is 32GHz e.g. https://www.tomshardware.com/reviews/pcie-definition,5754...

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Another round of speculative-execution vulnerabilities

Posted Aug 23, 2023 12:13 UTC (Wed) by excors (subscriber, #95769) [Link] (1 responses)

I think that may just be a different meaning of "frequency": the sampling rate is 32GHz, while the Nyquist frequency (basically the frequency of the sine wave corresponding to the worst-case signal 1010101...) is 16GHz. Same as describing audio CDs as 44kHz (the sampling rate) or 22kHz (the highest audio frequency that can be encoded without aliasing) - both are reasonable in different contexts.

For example https://blog.samtec.com/post/why-did-pcie-6-0-adopt-pam4-... describes the Nyquist frequency of PCIe 5.0/6.0 as 16GHz. (The sampling rate is also the same in both, the difference is that in 6.0 each sample encodes 2 bits, so it's 16GHz Nyquist frequency with 32GHz sampling rate and 64GT/s data rate.)

Another round of speculative-execution vulnerabilities

Posted Aug 23, 2023 13:14 UTC (Wed) by malmedal (subscriber, #56172) [Link]

Thank you, sounds plausible.