Hi Brian. Only a thought, but if the drive is very cold, the air density under the heads would be higher, and could possibly degrade its performance, increasing retrys and therefore latency etc. As the spinning platters frictively heat the enclosed air, head height normalises, and the drive settles down. I may be totally off base here, but the scenario would seem to fit the symptoms. Also, how "Cold" are we talking about here? Wiser heads than mine may come up with better ideas. Best regards, Morrie. From: luv-main-bounces@luv.asn.au [mailto:luv-main-bounces@luv.asn.au] On Behalf Of Brian May Sent: Monday, 17 November 2014 12:04 PM To: Luv Main Subject: Re: Computer issues with Linux On 8 September 2014 12:08, Brian May <brian@microcomaustralia.com.au> wrote: Any disk IO appears to make the wait go up excessively. Ok, after some false leads, still having problems. e.g. after bios update, the bios gets upset that CPU fan is spinning slower then expected (around 400RPM); it is a large fan with large heat sink with no signs of dust or damage, it spins freely and continues spinning for a while, so I think the BIOS threshold is too low and the fan is ok. The problem only occurs on cold days, and disappears after the computer has been left on for 30mins+, The CPU fan speed does not increase significantly in this time, and it is still considered too slow for the BIOS (had considered the possibility that the BIOS was throttling the CPU because it was upset with the fan, but I doubt it). I can't actually see any evidence of CPU throttling (not that I really know how to check; values in /proc/cpuinfo seem to be fine). What is most likely to cause the computer to run slowly when it is cold? -- Brian May <brian@microcomaustralia.com.au>