Yes I have noticed Prime blend needing more VTT, a good bit more for 4ghz with HT vs 3.8ghz with HT. But I have also noticed it needing slightly more voltage to make it through long Prime blend runs vs just burning through a quick LinX x 20.
Whenever I try a drastically different OC I start with LinX, watch it blow up really fast, keep upping voltage until it passes x 20. Then I go for blend and watch it work fine for a while.. and think it's stable. Then re-test and sigh... it isn't stable.
One thing that has been a warning sign that has held true for me every time is if I see three different voltages for Min/Max/Current in HW monitor after leaving Prime blend running for a while. It means my voltage is borderline and it's occasionally drooping too much. I'm jealous of these boards that put out more voltage than you ask for in the BIOS. I have to enable LLC just to keep it from sagging further (Gigabyte UD5).
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