Re: Centrino CpuFreq
Anders Breindahl schrieb:
On Thursday 09 December 2004 23:43, Dieter Jäger wrote:
I found a similar issue when I accidently loaded the "wrong" cpufreq
driver for P4 with powernowd. Suddenly /proc/cpuinfo showed frequencies
down to 200 MHz (the Bogomips also went down).
So I searched a little bit. People seem to think that those 600Mhz is
kind of hardcoded to the Centrino chipset. Taking a closer look to the
Intel Docu I found that the Intel specifications seem to be merely
recommendations. Other combinations of Frequency and Voltage are
possible. The docu regarding voltages clearly shows that there are
voltages possible other than those in the Freq/Voltage table.
I got curious and played around a little bit: On my centrino I could
lower the frequency down to 100 Mhz. Lower frequencies caused the
cpuinfo display to be messed, but frequency down to 100Mhz seem to be
stable. To be clear: Those tricks are not official language! But my accu
now works conspiciously longer :-)
I do not know wether this can cause some damage so I cannot recommend
doing such things.
Best regards
Dieter Jäger
I am very interested. Please provide a clue to how you did.
Regards, Anders Breindahl.
I did some changes in arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c:
These are the changes I tried: They set a lowest frequency of 100Mhz and
should change the core voltage to 0.716V. The 100MHz I found by trial
and error, the 0.716V I took from the voltage definitions in the Intel
Docu at ftp://download.intel.com/design/mobile/datashts/ . Icannot
remember which document, but it is mentioned in the kernel source. The
0.7V did not work on my Laptop (AcerTM660, Centrino 1600).
--- arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c 2004-06-16
07:19:13.000000000 +0200
+++ /tmp/speedstep-centrino.c 2004-11-18 15:22:47.000000000 +0100
@@ -171,6 +171,14 @@
/* Intel Pentium M processor 1.60GHz (Banias) */
static struct cpufreq_frequency_table banias_1600[] =
{
+ /* OP( 100, 700), */
+ OP( 100, 716),
+ /* OP( 100, 732),
+ OP( 100, 748),
+ OP( 100, 764),
+ OP( 100, 796), */
+ OP( 200, 812),
+ OP( 400, 844),
OP( 600, 956),
OP( 800, 1036),
OP(1000, 1164),
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