Messages in this thread | | | Date | Thu, 31 Mar 2011 07:19:50 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 2/9] x86 idle: remove NOP cpuinfo_x86.hlt_works_ok flag |
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On 03/31/2011 02:35 AM, Ingo Molnar wrote: > > * Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: > >>> Btw., we used to auto-detect broken HLT systems IIRC - but that got lost >>> already. We should at least honor the boot parameter. >> >> I don't believe we ever auto detected them or found a way to do so. That >> was why the HLT message was printed before hlt was executed. > > Yeah - the CPU hang was unrecoverably deep so no auto-detection was possible. > > That's seriously ancient stuff - still, keeping the boot option around (<10 > lines of code) does not hurt anyone. >
What it was was bad power supplies or low-capacitance, high-inductance power distribution that happened to work with MS-DOS which always burned the CPU at 100% and therefore left the power draw relatively consistent current. A proper OS putting the CPU in HLT produced a lot more high frequency noise on the power busses, with disastrous results without proper bypass.
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
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