From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: nearly-working support for cpufreq on 2004 iBook G4 with 7447Acpu From: Benjamin Herrenschmidt To: John Steele Scott Cc: linuxppc-dev list , Christiaan Welvaart In-Reply-To: <63605.192.43.227.18.1086055525.squirrel@www.toojays.net> References: <200405302331.35357.toojays@toojays.net> <200405311003.21439.toojays@toojays.net> <1085975390.1930.31.camel@gaston> <200405311807.59356.toojays@toojays.net> <1086047232.1930.74.camel@gaston> <63605.192.43.227.18.1086055525.squirrel@www.toojays.net> Content-Type: text/plain Message-Id: <1086058430.1954.3.camel@gaston> Mime-Version: 1.0 Date: Tue, 01 Jun 2004 12:53:50 +1000 Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: On Tue, 2004-06-01 at 12:05, John Steele Scott wrote: > > Oh, and when switching to high speed, think about tweaking the > > voltage too. I don't know if it's high or low when setting the > > GPIO bit, you may want to check out OF code, it certainly have > > methods for that. Or you can read the voltage value back from > > the adt themometer chip I think, as it does voltage control. > > I will double-check this tonight (am at uni now), but I thought that the > core voltage for this chip does not change with frequency . . . :( It probably does since there is a GPIO for controlling it on KeyLargo. It's not the chip itself that changes it, you use the GPIO to change it before/after the freq. switch. That's wher the real saving comes from, more than the freq change itself in fact. ben. ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/