A:Answer I mean, I *wouldn't recommend* severely mixing and matching extremely different RAM speeds (2666 vs. 3466).
*In theory,* they *might* work together, but if they did, your existing faster RAM stick would have to down-clock to match it, so you'd get higher capacity, but lower speed (2666).
And that's leaving aside any differences in brand, quality, latency differences, timings, etc., which could potentially cause instability in some situations.
Like, I'd go for something as close to what's already in your system as possible. Another stick of similar size, frequency, latency [CL17, etc.], etc.
Or get a matched pair that are designed to work together [dual-channel, etc.], and fully swap out the 1 stick for a matched pair... (Then resell the old stick to recoup some of the cost of the new sticks, once the new sticks are in an running reliably for a bit.)
