I'm not able to determine what "Augmented SSL" actually means for the 6000 series; it may just refer to software improvements in SSL decryption as I don't think there are any special hardware modules in the 6000 series beyond what Intel put in them. It also could be a reference to the upcoming Falcon accelerator card; supposedly the 6000 uses the same line cards as the 5000 series and the 5000 series will support Falcon. Although I haven't seen an explicit statement anywhere that the 6000 series will be able to use Falcon. It is a bit concerning that AES-NI is not currently supported on the 6000 series with kernel 2.6.18 as SSL decryption could definitely take advantage of that.
Here are the processors, along with their SPU benchmarks:
15600: 2x Intel Xeon E5-2630v3, 2.40GHz (Eight-Core), 7400 SPU
6500: Intel(R) Core(TM) i7-4790S CPU @ 3.20GHz (Eight-Core), 3400 SPU
6800: Intel(R) Xeon(R) CPU E5-2640 v4 @ 2.40GHz (Ten-Core), 8900 SPU
As far as 15600 vs. 6800 you can see that they use practically the same processor, the 6800 just uses a newer version with 2 extra cores which accounts for the performance bump. All the other specs at ark.intel.com (bus/memory speed etc) between the two are about the same, with slightly faster bus/memory speeds for the 6800 and some extra SmartCache.
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