On Fri, Jun 29, 2018 at 06:29:48PM +0200, Geert Uytterhoeven wrote:
> Are you sure you're not interchanging A8 and A9, cfr. Linux kernel commit
> e388b80288aade31 ("ARM: spectre-v2: add Cortex A8 and A15 validation of the
> IBE bit")?Yes. That is the main reason the A9 is faster than the A8 at the same clock speed by quite a bit. For example http://www.360doc.com/content/12/0806/14/350555_228637047.shtml says: Cortex-A9 has many advanced features for a RISC CPU, such as speculative data accesses, branch prediction, multi-issuing of instructions, hardware cache coherency, out-of-order execution and register renaming. Cortex-A8 does not have these, except for dual-issuing instructions and branch prediction. So the A8 still has branch prediction so it can keep the pipeline fed, even with in order execution. Spectre isn't really about out-of-order excution as much as it is about speculative memory accesses which some in-order execution chips have too. -- Len Sorensen
