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

Another round of speculative-execution vulnerabilities

Posted Aug 9, 2023 22:21 UTC (Wed) by mathstuf (subscriber, #69389)
In reply to: Another round of speculative-execution vulnerabilities by willy
Parent article: Another round of speculative-execution vulnerabilities

Another way to think about it: these signals are largely one-way communication. If it were round-trip, the speed of light would matter. But all that really matters is how accurately you can sample the wire for a signal (PCIe gen 6 can apparently do so 64 billion times a second).

And another way to sanity check things: if the size of space between communication endpoints limited your processing rate, we'd probably still be waiting for the first (quality) images from various Mars rovers.

At least I think that's somewhat closer than what Wol has as a model.

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Another round of speculative-execution vulnerabilities

Posted Aug 10, 2023 8:00 UTC (Thu) by Wol (subscriber, #4433) [Link] (1 responses)

No. I did say the model is based on communication *between* components, ie there-and-back.

Cheers,
Wol

Another round of speculative-execution vulnerabilities

Posted Aug 10, 2023 20:28 UTC (Thu) by rschroev (subscriber, #4164) [Link]

If I were to send you a good old-fashioned letter, it would take a day or 4 (or somewhat less or more, I don't actually know; the exact value doesn't matter for this discussion); a reply from you to me would take 4 days too; there and back is then 8 days. Does that mean that I can only send you a letter once every 8 days? Only when my letter needs information from your reply; in that case I have to wait until I get your letter. But in all other cases, I can easily send new letters while old ones are still in transit. The distance between you and me sets a lower limit on latency, but does not affect bandwidth. It's the same for communication in computer systems.