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 2015-06-21, 14:48 #1 wildrabbitt   Jul 2014 3·149 Posts meaning of regular flashes of hot lead Hi, one of machines which uses all 8-cores to do LL tests and does little else has a red led light on the front which flashes on about every second. I was wondering if this was because after each iteration it writes to the HD. Can anyone explain this thing for me?
 2015-06-21, 15:26 #2 chris2be8     Sep 2009 2·1,021 Posts What operating system does it run? Is it memory constrained? What do you mean by "little else"? Try temporarily stopping prime95 (check CPU use goes to near zero) and see if the LED still flashes. Chris
 2015-06-21, 20:29 #3 TheMawn     May 2013 East. Always East. 11×157 Posts It's probably the HDD activity light. I'm a little surprised that it's red. If you have other LED's are they also red? Find something that makes heavy use of your drive. This could be a disk cleanup utility or even just copying a big folder / file (a couple of GB if you have spare room) from somewhere to the desktop or something. (delete it after, obviously). See what the light does. The only other standard LED I know of is the power LED and if that's blinking then that might be a concern. If you think it's not an HDD activity light then you might want to open your case and look around the motherboard for any other lights that are on or blinking. Most of them are nothing to worry about: On my own motherboard, for example, I have one indicating which of the two BIOS'es I'm using, two indicating active PCI-E slots and one HDD activity light. EDIT: I should mention that the HDD light does blink a good bit normally. It's probably not Prime95 saving iterations because those take a relatively long time to save. You could double-check that the setting is correctly set for 30 minutes (or whatever you prefer). Last fiddled with by TheMawn on 2015-06-21 at 20:31
2015-06-21, 22:06   #4
chalsall
If I May

"Chris Halsall"
Sep 2002

23·32·7·19 Posts

Quote:
 Originally Posted by TheMawn It's probably the HDD activity light. I'm a little surprised that it's red. If you have other LED's are they also red?
Colour doesn't matter; the "blinky lights" may.

Under Linux "vmstat -n 1" can help you correlate (along with other tools).

 2015-06-22, 01:28 #5 kladner     "Kieren" Jul 2011 In My Own Galaxy! 2·3·1,693 Posts Can you trace the leads from the back of the LED, to the motherboard, and see what it is plugged into?
2015-06-22, 02:00   #6
chalsall
If I May

"Chris Halsall"
Sep 2002

23·32·7·19 Posts

Quote:
 Originally Posted by kladner Can you trace the leads from the back of the LED, to the motherboard, and see what it is plugged into?
Almost without question, this is the HDD activity LED (as TheMawn suggested, and you inferred).

Code:
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
0  0      0 10086992  73592 709352    0    0     0     0  352 1136  1  1 98  0
0  0      0 10087436  73592 709352    0    0     0   400  342 1188  1  1 99  0
0  0      0 10087364  73592 709352    0    0     0     0  334 1121  1  1 98  0
0  0      0 10087364  73592 709352    0    0     0     0  329 1105  1  1 98  0
0  0      0 10087364  73592 709352    0    0     0     0  351 1175  1  1 98  0
0  0      0 10087240  73592 709352    0    0     0     2  327 1132  1  1 98  0
0  0      0 10086992  73592 709352    0    0     0     0  355 1151  1  1 98  0
0  0      0 10086992  73600 709348    0    0     0    22  346 1196  1  1 97  2
0  0      0 10086868  73600 709352    0    0     0     0  331 1097  1  1 98  0
0  0      0 10086868  73600 709352    0    0     0     0  318 1107  1  1 99  0
0  0      0 10086992  73600 709352    0    0     0     0  370 1220  1  1 98  0
0  0      0 10086496  73600 709364    0    0     0     2  344 1170  1  1 98  0
0  0      0 10086496  73600 709524    0    0     0     0  367 1195  1  1 98  0
0  0      0 10084992  73608 709652    0    0     0    18  380 1423  2  1 96  2
0  0      0 10084760  73608 709512    0    0     0     0  402 1340  2  1 98  0
0  0      0 10082900  73608 709352    0    0     0     0  336 1089  2  1 98  0
0  0      0 10082776  73608 709352    0    0     0     0  395 1231  1  1 98  0
0  0      0 10082900  73608 709352    0    0     0     2  338 1154  1  1 98  0
0  0      0 10077688  73608 712272    0    0     0     0  472 1875  2  1 97  0
0  0      0 10077692  73616 712432    0    0     0    38  501 1792  2  1 95  1

 2015-06-22, 08:27 #7 wildrabbitt   Jul 2014 3·149 Posts Thanks for all the replies guys. Had a few beers last night so was AWOL for a while. Anyway, I've checked that the RED light I'm talking about was plugged into the HDD led socket on the front panel connectors and it is. (I took it out, the RED light stopped flashing and I looked in the mobo manual to see if it's the right two pins on the mobo and it is so I'm sure). BTW, I'm sure I was supposed to make something of that page of output Chalsall posted but I'm not able to.
 2015-06-22, 09:30 #8 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 24×3×7×19 Posts On some server motherboards there is a red light on the board itself which blinks when the machine is overheating (I have had some difficulty cooling my Xeon-D adequately, so got well acquainted with that light).
 2015-06-22, 10:29 #9 wildrabbitt   Jul 2014 3×149 Posts That might be it, but it's been doing it for months so if it is overheating it's not doing so enough to switch the machine off.

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