For several months I've been trying to track down the cause of frequent system freezes on a machine I built in Dec. '13. The frequency of freezes has gradually increased from never to several times a day. The solution is so improbable that I wonder if I am hallucinating. I simply moved the SATA cable from a SATA 2 to a SATA 3 socket on the motherboard. There are two hard drives: /dev/sdb - the primary ATA disk with several partitions that constitute the working Fedora 20 system. This is a Western Digital WD 2500BB-00G 250 GB with old-style 40pin ATA ribbon cable to the ATA socket on the mobo. /dev/sda - the secondary SATA disk, a 1 TB Western Digital WD10EACS-00D. This is used solely to save a backup image of another machine, updated by rsync every night at 10:30 PM. It has a SATA connector and, according to the newegg spec sheet, runs at 3.0Gb/s, which is SATA II. The SATA III spec runs at 6.0Gb/s. Except for the nightly backup, this disk is never used, or as Mr. James Clapper might say, never used "wittingly". The imponderable questions are: - why would plugging a SATA II disk into a SATA II socket produce random freezes? - why would plugging that SATA II disk into a SATA III socket NOT produce freezes and work well? - Is this behaviour indicative of defective SATA mobo sockets, defective ata software, defective hard drive implementation? Originally, I had used a Gigabyte 78MT-USB3 mobo, but replaced it with an ASRock 960M/U3S3 FX mobo in a futile attempt to fix the problem. For several months the original Gigabyte mobo worked fine - and then the freezes began. These may be the only two available mobo's with both the AM3+ cpu socket and an ATA disk socket. The Gigabyte mobo has only SATA II sockets - 6 of them, while the ASRock has 2 SATA III and 4 SATA II sockets. For completeness, I've tested all four SATA II sockets. All cause system freezes, one as quickly as 12 minutes, another as long as 20:27 hh:mm. In contrast, use of either of the SATA III sockets yield a stable system. When the system freezes, if X is lit (not screen-saved) the LCD monitor looks as if it had been hit a sharp blow on the right edge so that all the pixels have been shaken loose. All vertical lines are shimmering off to the right or left in quarter inch blocks. The image is still recognizable and almost readable. The NumLock key toggles its LED, but not the ShiftLock or ScrollLock. No other keys are alive including Alt-Fn-N, CTL-ALT-BS or CTL-ALT-Del. There's no mouse action. The ethernet card LEDs blink, but pinging from another machine fails. Only the Reset button, or the Power button, work. Before stumbling onto the SATA II -> SATA III solution, here are some things I tried, that failed: - Replaced the motherboard (as noted). - Added a second 4GB memory stick - Ran memtest86 for a day and a half without a single error - Watched the cpu temperatures and saw only normal values - Cleaned and reseated the cpu and applied new thermal grease - Disabled skype - Unplugged a USB camera and microphone - Removed a USB Logitech wireless kbd/mouse; replaced with wired ones - Converted the ATA primary disk to SATA via an adapter. Although not tested extensively, when plugged into a SATA II socket it ran OK. So, wizards, has any of you experienced a system freeze such as mine? Can you attribute it to connecting a SATA II hard drive to a SATA II socket? -- David A. De Graaf DATIX, Inc. Hendersonville, NC dad(a)datix.us www.datix.us Q: Why do programmers confuse Halloween and Christmas? A: Because OCT 31 == DEC 25.