Microsoft Advice Against Nehalem Xeons Snuffed Out

Eukariote writes "In an article outlining hidden strife in the processor world, Andreas Stiller has reported the scoop that Microsoft advised against the use of Intel Nehalem Xeon (Core i7/i5) processors under Windows Server 2008 R2, but was pressured by Intel to refrain from publishing this advisory. The issue concerns a bug causing spurious interrupts that locks up the Hypervisor of Server 2008. Though there is a hotfix, it is unattractive as it disables power savings and turbo boost states. (The original German-language version of the article is also available.)"

Comments

What about for Windows 7?

[Faizdog]

This story is interesting and timely because I plan on buying a new desktop in the next 2 weeks, just waiting for the right deal to come out, hopefully on Cyber Monday. While not getting a server, I will be getting Windows 7. I had been planning on an i7, but now am hesitant. Is there a problem with these processors for home use/gaming purposes under Windows 7? Or would I better off going with a Quad Core?

First Rev of New Architecture

[bill_mcgonigle]

Many of the benchmarking sites have also posted some poor results - I was thinking this might be a generation to skip, but now I wonder if a flaw has been discovered that could be fixed with a microcode upload. Might help the benchmarks too if it was a hidden variable.

Re:Isn't it really a bug in Windows Server?

[AcidPenguin9873]

I don't think so. Here's the text from the Intel erratum:

During a complex set of conditions, if the APIC timer is being used to generate interrupts, unexpected interrupts not related to the APIC timer may be signaled when a core exits the C6 power state. The APIC timer stops counting in C6 and as such isn't typically used to generate interrupts when the C6 core power state is enabled. Implication: Unexpected interrupt vectors could be sent from the APIC to a logical processor.

Interrupts not related to the APIC timer being caused by the APIC timer is not a software problem, it's a hardware problem. I could understand your argument if the APIC timer was generating too many interrupts upon C6 exit, or something else related to messed-up APIC timekeeping near power management events, but this is unrelated interrupts being generated.

I don't know the details, but I would assume Microsoft is using the APIC timer in its hypervisor for a reason. Maybe it's because the hypervisor is required to virtualize all the other timekeeping mechanisms for the guest.

MS KB DOES NOT say hotfix breaks power save

[George_Ou]

Folks, this is a very irresponsible headline at slashdot. The Microsoft articles does NOT say hotfix breaks power save and it doesn't even mention turbo, but that it is an either or solution. Microsoft always offers workarounds as an ALTERNATIVE to the hotfix for people who don't want to apply hotfixes. The Microsoft KB article even tells you if you want to keep using those power states, then run the hotfix and make a certain modification to the registry.

This post makes it sound like some kind of cover up and that the fix causes major CPU slowdowns, and that it's on the level of the AMD Barcelona TLB bug where the fix actually did cause a significant performance drop. This does not appear to be true. The real story is that all CPUs have hundreds of errata, and it's the job of the software maker to work around it, and that is what Microsoft is doing with their hotfix and registry hack. They're also telling you if you aren't experiencing any problems, don't bother applying the hotfix.