Hi John, Yes. There are still AMD CPUs sold without SSSE3. Most notably Athlon. Instead, Intel is providing SSSE3 from the Core 2 Duo. A detailed list is available at: http://en.wikipedia.org/wiki/SSSE3 Ciao, Andrea On Wed, Nov 20, 2013 at 7:09 PM, John Williams <jwilliams4200@xxxxxxxxx> wrote: > On Wed, Nov 20, 2013 at 2:31 AM, David Brown <david.brown@xxxxxxxxxxxx> wrote: >> That's certainly a reasonable way to look at it. We should not limit >> the possibilities for high-end systems because of the limitations of >> low-end systems that are unlikely to use 3+ parity anyway. I've also >> looked up a list of the processors that support SSE3 and PSHUFB - a lot >> of modern "low-end" x86 cpus support it. And of course it is possible >> to implement general G(2^8) multiplication without PSHUFB, using a >> lookup table - it is important that this can all work with any CPU, even >> if it is slow. > > Unfortunately, it is SSSE3 that is required for PSHUFB. The SSE3 set > with only two-esses does not suffice. I made that same mistake when I > first heard about Andrea's 6-parity work. SSSE3 vs. SSE3, confusing > notation! > > SSSE3 is significantly less widely supported than SSE3. Particularly > on AMD, only the very latest CPUs seem to support SSSE3. Intel support > for SSSE3 goes back much further than AMD support. > > Maybe it is not such a big problem, since it may be possible to > support two "roads". Both roads would include the current md RAID-5 > and RAID-6. But one road, which those lacking CPUs supporting SSSE3 > might choose, would continue on to the non-SSSE3 triple-parity 2^-1 > technique, and then dead-end. The other road would continue with the > Cauchy matrix technique through 3-parity all the way to 6-parity. > > It might even be feasible to allow someone stuck at the end of the > non-SSSE3 road to convert to the Cauchy road. You would have to go > through all the 2^-1 triple-parity and convert it to Cauchy > triple-parity. But then you would be safely on the Cauchy road. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
