On Wed, 26 Nov 2008, Norbert van Bolhuis wrote: > Thanks for the answer, but that's not it. > > I checked the jiffies variable, it increases about 250 times > per second. > So the (mpc83xx_defconfig) kernel perception (#define CONFIG_HZ 250) is OK. > > It must be something else, I still think 83.20 BogoMIPS > can't be correct for a MPC8313 running at 333 MHz.
On PPC, BogoMIPS depends on the decrementer frequency, not on the CPU clock. Check `timebase' in /proc/cpuinfo, which is e.g. 79.8 MHz on a PS3 (while the actual Cell processor runs at 3.2 GHz). That's why the PS3 gets only 159 BogoMIPS. > Alessandro Rubini wrote: > > > This is what a linux-2.6.x reports (for the MPC8313E running at 333 MHz): > > > Calibrating delay loop... 83.20 BogoMIPS (lpj=166400) > > > > > > Which can't be correct. > > > > > > A MPC870 (running at 133 mhz) has ~ 131.07 BogoMIPS > > > > Actaully, one-instruction-per-clock leads to BogoMIPS = MHz. > > > > Your "loop per jiffies" value shows you make 332800 instructions per > > jiffy (a loop is two instructions: increment and jump). > > > > So most liker your timer tick runs at 1000 Hz but Linux is thinking > > it's at 250Hz (332800 * 250 = 83.20 millions). > > > > > Of course it's only a benchmark figure. > > > > No, it's not a benchmark figure. It's the metric by which udelay() is > > calculated. So your udelays (and mdelays) will be 4 times shorter than > > required, and some hardware may be misbehaving as a result. > > > > Hope this help > > /alessandro, who however is not runing a powerPC these times With kind regards, Geert Uytterhoeven Software Architect Sony Techsoft Centre Europe The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium Phone: +32 (0)2 700 8453 Fax: +32 (0)2 700 8622 E-mail: [EMAIL PROTECTED] Internet: http://www.sony-europe.com/ A division of Sony Europe (Belgium) N.V. VAT BE 0413.825.160 · RPR Brussels Fortis · BIC GEBABEBB · IBAN BE41293037680010 _______________________________________________ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded