Severely degraded harddisk performance on sata_sil by athcool

I am writing this post to provide some statistics on athcool + sata_sil usage. The results are horrible.

Athcool is a small utility, enabling/disabling Powersaving mode for AMD Athlon/Duron processors.
The homepage of the utility has a big fat warning as well:

WARNING: Depending on your motherboard and/or hardware components, enabling powersaving mode may cause:

* noisy or distorted sound playback
* a slowdown in harddisk performance
* system locks or instability

The Gentoo ebuild also has these warnings:

ewarn “WARNING: Depending on your motherboard and/or hardware components,”
ewarn “enabling powersaving mode may cause:”
ewarn ” * noisy or distorted sound playback”
ewarn ” * a slowdown in harddisk performance”
ewarn ” * system locks or unpredictable behavior”
ewarn ” * file system corruption”
ewarn “If you met those problems, you should not use athcool. Please use”
ewarn “athcool AT YOUR OWN RISK!”

Ignoring all these warning I was using athcool for years on my old desktop box filled with 2 IDE disks. Never had any real problem at all, except for a some performance loss. The problem appeared when I first used a sata disk on motherboard’s, Gigabyte GA-7VAXP-A Ulta, sata controller which uses the sata_sil module.