VTT / VDIMM etc... Mythbust attempt

[saaya]

Secondly, if the setup doesn't die you've proven nothing because of the small amount of test sample. If it does die, you've reconfirmed the myth. So, there's no positive end to this thread (at least for you).

well, its unlikely that the difference between the chips is huge, and its mathematically unlikely that he ended up with one of the rare best case or worst case chips, so its possible to at least get an idea of where the limit is... lets say his chip burns with a vtt/vdimm delta of .8v after a few weeks, then thats enough info to conclude that running more than a .6v delta isnt a good idea 24/7...
theres always SOMETHING, a rough idea, you can conclude from sample testing... but yes i agree, its far from enough to prove a myth exists or doesnt... as soon as .1% of cpus dies from a certain voltage setting, there will be several reports about it online, and the myth will live on...
thats something most people dont understand, the difference between 99% safe voltages and 100% save voltages is huge ^^

Thirdly, the VTT/VDIMM safety zone for Lynfield is TIGHTER than the one for Bloomfield. Apparently not many people are aware of this, although some hardware websites have made this public already. Just read this page: link.

wow i didnt know that... and yes, its not "xs" who came up with this myth, its intel... they were the ones who told several enthusiasts, the entire press, and all mainboard and memory makers of how sensitive nehalem based cpus are to a vtt vdimm delta. and they exaggerated quite a bit, probably to scare people... they originally claimed 1.8v vdimm with 1.1v vtt would kill a cpu within days if not hours. for some b0 samples that was actually true (happened with 2 chips at foxconn) but c0 was a lot tougher and d0 even more... i only heard of 2 d0 chips that MAYBE died from a bad vtt to vdimm ratio.

oddly enough, gulftown es chips seemed to have a very similar problem again, and again the retail chips seem ok...

i totally agree with the madshrimps article btw, how come intel still cant come up with a robust vtt/vdimm design like amd?

marc, id say go for voltages that make sense first.
push for the highest vdimm your mem still scales with under ln2, with high vtt... or maybe push vdimm even higher than it scales to check if higher vdimm is still ok.
then reduce vtt and see if a 1v delta is ok for benching several sessions.
if there is no degradation, then thats good news...
then test on air, again increase vdimm with vtt until it doesnt scale anymore, maybe a bit higher...
then reduce vtt...

i dont think that there will be degradation or dead chips from this... you probably have to run huge vdimm with ridiculously low vtt to run into issues... and that just doesnt make sense...
so even if you degrade or destroy a chip, its will probably be pretty useless cause nobody would ever run those voltages so far apart from one another...
all you would prove then is that its possible to kill a cpu with too high voltages... which is nothing new