New box, new Mint, same CPU but only half the performance?

[bjornmu]

I have a strange problem with my new desktop. It has the same CPU as the old one: a 6-core AMD FX-6300 and even the same mother board ASUS M5A97 R2.0 (both boxes shipped without OS). The old box is running Mint 14, the new is on Mint 17.

The BogoMIPS number reported at boot is almost exactly the same for both, but the new box gets only about half the performance! I am running SETI@Home and the floating point benchmark there says 2617 MIPS per CPU on the old one, only 1366 on the new. I also ran a banal test program adding one billion different square roots, it takes twice as long on the new box. Integer arithmetic is also affected.

I can confirm that all cores are running on the max. frequency 3.50 GHz so that's not the issue, I can even hear the fans picking up when I start SETI@Home.

I do notice one difference. cpufreq_info -c 0 -d on the old box reports 'powernow-k8' as the driver, while on the new box it's 'acpi-cpufreq'. Can that be the problem? And if so how do I fix it?

In /var/log/kern.log/1 which I think is from the initial boot, I can see a number of lines like this:

Jun 7 14:01:03 igil kernel: [ 1.883896] acpi-cpufreq: overriding BIOS provided _PSD data

[bjornmu]

Now here's an even stranger thing: on the Mint 14 box it takes 2.5 times longer to run my simple floating point test program from mate-terminal that from xterm of from an ssh session from the other box. How can that be????

With higher optimization it still takes 50% longer to run on Mint 17 than 14.