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

Re:Broken processors

[Anonymous Coward]

We use them with Oracle VM (Xen), and they work ok.

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?

Re:What about for Windows 7?

[Anonymous Coward]

I may be wrong, but if they said IO-APIC, then it's probably due to that normally being in the northbridge (I BELIEVE!) and thus in the case of the i920 not actually on-chip. The difference being the LGA1156 series chips have almost all, or all the northbridge functionality on-chip (PCIe channels are from the CPU, not a northbridge like on the LGA1366 series hardware). So possibly it was something that was noted, but not considered a problem for the segment the chip was aimed at, wasn't an issue that came up in testing with previous microsoft virtualisation or anybody else's (which probably got more thorough testing), and upon release it turned out 'ooops, people actually ARE going to use it for that purpose and we didn't do something smart like pressure microsoft to change their interrupts so it won't fall on us.'

But hey, what do I know, right?

Re:What about for Windows 7?

[omfglearntoplay]

Be sure to avoid any of the HP i7 processor models. They have a major motherboard problem, as I have luckily learned myself by buying one. Check some googling with HP i7 crash freeze, etc. Or go here to see gobs of users with problems:

http://h30434.www3.hp.com/psg/board?board.id=lockups

However, I hear that home made PCs on i7 platforms are fine as well as recent Dells. I'm going the Asus motherboard route to rectify my problem. It's just grand though b/c they are way expensive, then I need a new case (b/c HP uses the lefty cases), and I need a new heat sync/fan (b/c HP is proprietary). So to fix my $1200 HP, I have to spend 5 or 6 hundred. WEEEE!

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:VMWare may also be a problem

[Glasswire]

Is it in response to a documented problem with VMWare ESX that HP trying to remedy with a specific BIOS change or is HP just flailing around suggesting BIOS updates as a fix to a problem they don't yet understand? There are 100s of reasons why you're having VMWare lockup issues - the ONLY similarity to MSFT issue that you seem to have is they are both hypervisors running on Nelhalem procs. Pretty thin. What does VMWare think the problem is?

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.