I've been chewing on this for a week or so. Thought I'd ask if it could be validated. My thoughts are based on reading the Spectre whitepaper and research on the AMD K8 microarchitecture, and haven't been able to find any AMD K8 specific Spectre related info on the web. I'm also not a computer science dude... So here it goes:
AMD K8 processors are possibly not vulnerable to Spectre variant 1 (exploiting conditional branches) as although the processor does have an out-of-order execution paradigm, memory operations are executed in-order; memory access cannot be reordered. So if a memory read gets stuck, it would stall all subsequent memory reads or writes, thus eliminating the attack.
The AMD K8 processors are also possibly not vulnerable to Spectre variant 2 (exploiting indirect branches) as although the processor does have branch predictors, it doesn't have indirect branch predictors. Meaning, that the processor will just go to the same target/branch as it did the previous time. Therefore, the processor cannot be trained to make a misprediction nor mistrained, thus eliminating the attack.
Thanks to all the responses.