Fwd: VAX + Spectre

[Cameron Kaiser]

> "Spectre" is one of two notorious bugs of modern CPUs involving speculative
> execution.  I rather doubt that VAX is affected by this but I suspect others
> here have a lot more knowledge.

However, even speculative execution isn't enough to make Spectre possible or
feasible. For example, the PowerPC G3 and 7400 CPUs speculatively execute,
but because indirect branches can only be done on special-purpose registers
and the G3 and 7400 halt speculative execution until the SPR is loaded with
the destination address, this means they won't speculatively execute after
any indirect branch in code and makes them resistant to the currently known
variants of Spectre.

Given how weird the VAX can be in some respects, I wouldn't be surprised if
similar idiosyncratic behaviours exist that confound such attacks similarly.

http://tenfourfox.blogspot.com/2018/01/actual-field-testing-of-spectre-on.html

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  Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser at floodgap.com
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