Topic Title: A10-5800K throttling
Topic Summary: throttling
Created On: 04/07/2013 10:51 AM
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 04/07/2013 10:51 AM
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joeyjojojjjjjj
Peon

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Joined: 04/07/2013

Well I can usally figure things out without help but this time I need some help.  I have a biostart hifi A85S3 motherboard with an A10-5800K.  The issue I am having is the APU will throttle under 100% load (prime95).  The multiplier will drop to 14x and the mhz per core will drop to 1397mhz.  It will stay there for a min or two then jump back up to 38x multiplier.  All the Bios options are set to auto and the temps are fine with a max of 30C under full load.   I also observed this throttling while compiling mame.  Why is the APU doing this with stock clocks and acceptable temps?

 

Update:  After a few hours of messing with this setup I have not figured out why the APU is throttling.  I can overclock it to 4.4ghz and it throttles the same as when its at stock speeds.  It only happens at 100% load.



Edited: 04/07/2013 at 11:37 PM by joeyjojojjjjjj
 04/10/2013 08:55 AM
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joeyjojojjjjjj
Peon

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Joined: 04/07/2013

I think I found the answer.  This IS a problem with the processor.  I found this...

The popular hardware web site X-bit Labs has recently discovered an unannounced peculiarity of the latest Trinity APUs by AMD – when under load the chips operate at a clock speed that is even lower than the nominal one which negatively affects performance.

The peculiarity was noticed by the X-bit Labs staff when testing the latest Trinity chips against Intel Ivy Bridge processors. As any other chip AMD Trinity APUs have nominal clock speeds, idle clock speeds and Turbo clock speeds that are only active during certain circumstances and when AMD Turbo Core is enabled in the system’s BIOS. Unfortunately for AMD Trinity owners though it was discovered that the Trinity chips drop their clock speeds even below the nominal speed when under full load.

For example the AMD A10-5800K APU has a default clock speed of 3.8 GHz and is capable of Turbo Boost clock speed of 4.2 GHz but during high multithreaded loads the clock speed gets lowered to 3.4 GHz and not to 3.8 GHz as the chip’s TDP exceeds the specified value. All other Trinity chips exhibit the same behavior but the really weird thing is that this phenomenon is not observed when AMD Turbo Core is disabled – in this case the A10-5800K chip operates at 3.8 GHz when under heavy load.

AMD has confirmed the issue but claims it appears only in very rare cases when the chips are under load that is not typical for client microprocessors. “Linpack is one of the few synthetic applications that may exceed the de-rating defined for our TDP. In the synthetic instances where base frequency causes our APU to run above its TDP, the part will throttle down to a frequency below base. Similar to Intel, thermal design power (TDP) is a realistic power target for partners to use in order to provide the best balance between cost and performance.  However, as stated above, some unusual and synthetic workloads can cause a thermal event where our APU briefly drops below the base frequency.”, AMD said.

 

 

This is not a rare problem.  I  have seen this while compiling mame.  This is BS if you ask me.  I paid for a processor that can run a task at 3.8ghz and I get one that "drops out" every 30 seconds, slowing to 1.4ghz on all cores.

 

Anyone else want to check this out with prime95.  Should take under 3min until the cores downclock to 1.4ghz.  Use hw64_416 to see the mhz of each core, then run prime95.  You can also use CPU-z to see the apu mhz but only shows one core.

 04/10/2013 11:23 AM
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joeyjojojjjjjj
Peon

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Ok great forum here btw.  Here is what I have found.

This is some real BS if you ask me.  I paid for a processor that could run 3.8ghz under 100% load, 100% of the time.  What I got is a processor that can run at 3.8ghz for a percentage of the time but when the numbers really start crunching it down clocks.  Oh sure you can clock this baby all the way up to 4.5ghz, and it will say in cpu-z 4500mhz but if you monitor the cores frequency you will see that it will down clock them all the way to 1.4ghz, what good is the overclock then?

Don't believe me?  A10 owners, grab the utility HWiNFO64 and a copy of Prime95.  Set the APU to turbo core off, giving you a 3.8ghz quad core.  Run prime and watch your cores drop to 1.4ghz in under 5min.  They will stay there for about 10 seconds and then jump back up,  The cycle will repeat at a quicker interval over and over. You can monitor cpu useage and it will be 100% and Prime95 will give no errors but your cores are running at 1.4ghz part of the time!

Don't think this happens only when turbo core is on because it happens anytime you tax the A10-5800k to 100% for over a min or two.  Try it.



Edited: 04/10/2013 at 11:43 AM by joeyjojojjjjjj
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