Once installed memory defaulted to 1333mhz on my Gigabyte GA-990FXA-UD3 - AM3+ motherboard running a AMD FX6100 Bulldozer cpu. I fiddled about in BIOS changing RAM frequency and multipliers and nothing would 'stick' it always defaulted to 1333 at POST with a warning message saying I can't overclock this memory. After a bit of confusion I realised that this memory is 1866 out of the box. So back in BIOS I looked for the SPID settings and after a while I found the RAM's profile in BIOS simply listed as "Profile 1". Selecting this got the RAM up to its operating speed of 1866mhz and everything is fine now. My Windows Experience Index is 7.7 for this memory bearing in mind I am running a 6 core processor at mininmum 3.3ghz and turbo charges up to 3.9ghz when only a few cores are being used.
So very pleased, memory is stable, comes in packaged pairs so I'm guessing they have been tested together. Delivery is a little long but I would buy again this memory from this seller.