It used to be much easier to discover which stick is bad before dual and triple channel memory.
Consider putting them both in the same channel and doing memtest, that should help you figure out which one is bad, if it's not both.
But if they're the same part from the same batch, chances are good they're both marginal, and you'd be better off replacing both.
They’re already on the same channel, and it looks like only the lower region is bad, and memtest86+ shows which slot is which region, so I might already know, but since there are only two sticks it’s not like I can’t remove one and rerun the test one more time. If it passes, it’s the one I removed. If it fails, then I have to swap sticks and run a third time to make sure they aren’t both failing.
They ARE both the same part, but I don’t know if they’re from the same batch. They’re top-tier memory, though (Corsair), so I expect the company will stand behind them. We’ll find out when I contact them tomorrow, though.
Failing everything else, I have 6 4GB and 2 8GB sticks I can “borrow” from another computer I’m not using to get by if I need to.
—Patrick