Date: Sun, 03 Jul 2005 00:37:14 -0000 From: Maxim Sobolev <sobomax@portaone.com> To: Chuck Swiger <cswiger@mac.com> Cc: acpi@FreeBSD.ORG, current@FreeBSD.ORG Subject: Re: patch: p4tcc and speedstep cpufreq drivers Message-ID: <421EE81C.3040204@portaone.com> In-Reply-To: <421E5E7B.5040104@mac.com> References: <20050224011924.992A65D07@ptavv.es.net> <421DA0B5.4060705@portaone.com> <421E42F2.6010105@root.org> <421E49D9.60803@portaone.com> <421E5E7B.5040104@mac.com>
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Chuck Swiger wrote: > Maxim Sobolev wrote: > >> Nate Lawson wrote: > > [ ... ] > >>> "On-Demand mode may be used at the same time Automatic mode is >>> enabled, however, if the system (tries to enable the TCC via >>> On-Demand mode[1]) at the same time (automatic mode is enabled[2]) >>> AND (a high temperature condition exists [3]), the duty cycle of the >>> automatic mode will override the duty cycle selected by the On-Demand >>> mode." >>> >>> Since automatic mode is set by the BIOS before we even boot, things >>> should be fine. >> >> >> Well, this is quite tricky part of the spec. My reading is that the >> paragraph above applies only to situation if you are (trying to set >> on-demand mode [1]) when both (automatic mode is in effect [2]) *and* >> (high temperature condition already exists [3]), in that case >> automatic mode will win and override any manual settings. > > > I suspect you'd read your paragraph with [1] and [2] joined together, > but they can be read seperately just as the spec can. :-) > >> However, in the case when you have on-demand mode already on and high >> temperature condition emerges it will have no effect on duty cycle >> until THERMTRIP# kicks in. >> >> That's in my view explains why there is big AND in the text above. > > > I think the spec is advising developers who try to control TCC that if > PROCHOT gets asserted, the CPU may override the programmed settings in > favor of the automatic ones. I don't think the spec is asserting that > the CPU is forbidden from reducing power usage if PROCHOT condition is > detected, regardless of what automatic mode is set to. > > A reasonable processor would drop to a known minimal power usage state-- > hopefully one low enough to keep the CPU from completely overheating > even if a fan has failed-- if PROCHOT is seen. > > [ It may also be the case that a CPU does not do so, in which case the > ACPI driver code ought to try to pay attention to PROCHOT and reduce > power consumption regardless and not just depend on CPU failsafes to > work. If that is your position, well, I would agree with this. :-) ] Check the original spec, there is a note at the end of the respective paragraph (particularly the first sentence): If automatic mode is disabled the processor will be operating out of specification and cannot be guaranteed to provide reliable results. Regardless of enabling of the automatic or On-Demand modes, in the event of a catastrophic cooling failure, the processor will automatically shut down when the silicon has reached a temperature of approximately 135 °C. At this point the system bus signal THERMTRIP# will go active and stay active until RESET# has been initiated. THERMTRIP# activation is independent of processor activity and does not generate any bus cycles. If THERMTRIP# is asserted, processor core voltage (Vcc) must be removed within the timeframe defined in Table 16. -Maxim _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org"
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