Ryzen CPU HyperThreads break if 100% busy and interrupted to top of Memory

Post by shizzlest » Sat, Aug 05, 2017, 11:51 AM UTC

gruez wrote: post #32

paulmd wrote: post #29

Earlier quoted context omitted.

AMD's not doing a recall, it works decently enough for most applications. Their response is going to be "if it crashes your application, turn SMT off". Consider they didn't even do a recall when Phenom had a showstopping TLB bug, they shipped a BIOS patch that disabled TLB entirely. And remember, Epyc is on a new stepping of the silicon, it's possible this is already fixed on it. (Threadripper is not, however)

> Their response is going to be "if it crashes your application, turn SMT off". it happens when SMT is disabled >Epyc is on a new stepping of the silicon, it's possible this is already fixed on it. (Threadripper is not, however) that's assuming they caught this bug, which i doubt is the case because it's only discovered now rather than being documented in the errata.

Post by grwthckrmstr » Sat, Aug 05, 2017, 12:51 PM UTC

paulmd wrote: post #29

StillBored wrote: post #15

Its like we have all collectively forgotten that the first release of a hardware or software project is just an expensive beta. I don't buy 1st gen microarches because i'm not interested in paying top dollar to be a tester. What I find odd, is that apparently both intel and AMD have also forgotten this, as Intel seems to be moving toward making their enterprise customers the beta testers, while AMD seems so desperate…

AMD's not doing a recall, it works decently enough for most applications. Their response is going to be "if it crashes your application, turn SMT off". Consider they didn't even do a recall when Phenom had a showstopping TLB bug, they shipped a BIOS patch that disabled TLB entirely. And remember, Epyc is on a new stepping of the silicon, it's possible this is already fixed on it. (Threadripper is not, however)

Post by dogma1138 » Sat, Aug 05, 2017, 2:24 PM UTC

nisa wrote: post #62

daurnimator wrote: post #44

Earlier quoted context omitted.

Someone was chatting to me today about picking up X5670 cpus for $50-$60. Compared to my 6600K they seem quite competitive: http://ark.intel.com/compare/83352,88191,47920

If you don't need good single thread performance and don't care about Performance/Watt that much you can get used servers for very little money with lot's of DDR3 memory (128GB+) and these X5670 als dual cpu systems. If you don't do anything fancy you get 80% of performance for 20% of the price of a new system.

Post by dogma1138 » Sat, Aug 05, 2017, 2:34 PM UTC

old-gregg wrote: post #38

powercf wrote: post #37

I hoped this just affected Ryzen CPUs, but this Reddit post indicates that it affects Epyc also: https://www.reddit.com/r/Amd/comments/6rmq6q/epyc_7551_minin... The first post on on AMD's community forum ( https://community.amd.com/thread/215773?start=0&tstart=0 ) is almost three months old, so AMD have known about this for a long time. If it's not something that can be fixed in a UEFI update, then it's bad news for…

So he's got a segfault every couple of minutes, wow... I've been running the same test for over 4 hours now on my Ryzen 1700 (and I've had several uneventful 30-40 minute runs before). To date, I only got one "internal compiler error: Illegal instruction" but no segfaults. Whatever it is, it doesn't affect every chip the same way.

Post by pella » Sat, Aug 05, 2017, 4:39 PM UTC

pella wrote: post #33

Phoronix: "Ryzen-Test & Stress-Run Make It Easy To Cause Segmentation Faults On Zen CPUs" https://www.phoronix.com/scan.php?page=news_item&px=Ryzen-Te...