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Scythe Kabuto - underperforming?

Tags:
  • Heatsinks
  • Cooling
  • Overclocking
Last response: in Overclocking
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March 26, 2010 10:49:49 AM

Greetings all,

I own following PC:

AMD 955 BE (C2) @ 3.2 GHz (stock settings)
Gigabyte MA-790-FX UD4P
2 x 2 GB DDR3 Corsair @ 1333 MHz, timings 9-9-9-24 (stock settings)
2 x WD 640 GB Caviar Black
Sapphire Vapor-X HD4890 @ 870 / 1050 (stock settings)
Gigabyte Setto 1000 case (2 x 120 mm silent fans)
Corsair TX 650W

and have installed Scythe Kabuto cooler 3 weeks ago.

On stock cooler, my processor would reach 62°C in one-two minutes when tested with Prime95, removing of the side cover did not help.

I have installed Scythe Kabuto, using thermal paste which came with the cooler, have used piece of one old credit card to create a thin layer of paste and the cooler was fit.

Now after running Prime95 for 2 hours, CPU temp goes to 55°C but not more. When removing side cover, temp drops to 48-50°C.

What I'd like to know, are these the results this cooler should be giving, or should I try reinstalling the cooler with some other thermal paste (like Arctic Silver 5 or some other brand paste).


I'd like to try overclock the CPU a bit, but I don't want the CPU to overheat. What is the temp limit for this CPU for 24/7 use?

Thank you for your answers.

More about : scythe kabuto underperforming

a b K Overclocking
March 26, 2010 2:28:38 PM

You might have put too much paste.

Check your case airflow. If you have it done right, removing the side panel won't make a difference. It looks like you don't have enough fans to push hot air out of your case. You've got hard drives gnerating heat and you've also got a notoriousl hot GPU.

My 955 BE OC'd to 3.6 GHz won't go past 58 after an hour of Prime95 and I'm running a Cooler Master HyperTX3 (Newegg $15 sale w/free shipping). I used about a bb sized drop that I spread in 3 very thin lines where the heat pipes contact the CPU.

On idle, my 955, still OC'd to 3.6 Ghz, runs at 37 C.

a b K Overclocking
March 26, 2010 2:33:21 PM

To be honest, your temps should be safe(your heatsink is more for quiet then anything, not that it is a bad cooler by any means). AS5 may improve things, but it would only be a few degrees at best(provided the heatsinks are installed the same way). If you have a smart fan option in the hardware monitor section of your bios, shut it off.

A question for you. Is it just me or was the stock heatsink for that cpu insanely loud.

EDIT
The side panel thing has allot to do with the case. Antec Sonata with the panel off drops temps a lot. With the Antec 900(no front fans on mine so the hard drive temps go UP with the side off), not at all.
a b K Overclocking
March 26, 2010 3:08:37 PM

Yeah, the C2 revision of the Phenom II 955 runs a bit hot. 55C while running Prime 95 for 2hrs isn't bad. As previously stated though, that scythe is more for silence. Arctic silver 5 will only help slightly, but really you should have used it the first time ^_^. Anyway, you do have some overclocking headroom. Remember, the temps you get while running Prim 95 for two hours aren't the temps you're going to get running normal day to day applications.

I'd say if your CPU stays under 62C after stressing Prime 95 for two hours, then you're still good. It really just depends on your sample since some people can only get a little below 3.8GHz, while others get 4.0GHz. Of course, if you are aiming for 4.0GHz I think you need more aggressive (which will also mean louder :D  ) cooling.
a b K Overclocking
March 26, 2010 3:18:27 PM

I also want to point out that earlier versions of the Phenom II 955 did not have properly calibrated thermal diodes. AMD didn't fix this until the 140W 965, which was still a C2 chip. As a result, your thermal readings may be a little off, depending on if you got a C2 chip after, or before, AMD finally got around to properly calibrating the thermal diodes. As far as I know C3 chips don't have that issue :D .
March 27, 2010 10:41:34 AM

Thank you for the replies.

@ hunderdisland: Air flow in case surely isn't the best as the case is not large and equipped with 2 x 120 mm "silent" fans, which perhaps I will consider replacing.

The hard drives are situated in the lower HDD case - the backup one is on the lowest position and the primary one is in level with the center of the front intake fan. I can not place it higher because GPU is blocking the place, and I don't want to put the hard drives too closely.

The GPU runs at 55-60 C idle, up to 72-73 C under full load - actually it seems it's a very good result for a HD4890.


The thermal paste I've applied in following way: placed one "grain of rice" sized drop on the CPU, then smeared the thermal paste all over the CPU, however all the time removing the excessive paste, so that in the end the layer was so thin that the numbers on the CPU could be seen.


@ nukemaster: I have the smart fan option, but it doesn't make a difference as the fan is running at max. 1400-1500 rpm and as per some of the tests I've done, it doesn't affect the temperature. Fan is definetly silent (as are the others), even with the side panel open, they are close to perfectly silent.

The side panel has perforations where the old heat pipe used to be. With the heat pipe in place, the stock fan ran up to 3000 rpm and was bearable. If I'd remove the heat pipe or remove the side cover, the stock fan would speed up to 6000 rpm and was indeed buzzing and loud - of course, the increase of the rpm did nothing for the cooling effect.


@ megamanx00: What I'd like to know is, can the CPU always (24/7) safely operate on 60-61 C, or are these temps also too high for continuous use?


I'd say I have problems with the case - first I can not fit any tower coolers, and low profile coolers have difficulties handling a 125W CPU, which is why I chose Scythe Kabuto, and perhaps I will have to replace the stock fans on the case.

Still I am interested to get as much as I can from the system I currently have - it didn't come cheap :D 
a b K Overclocking
March 27, 2010 3:05:22 PM

If you're handy with a drill and sheet metal work, consider drilling or cutting the top of your case and installing a fan to suck out or push out hot air.

Or, change your CPU cooler to something better, one that can use a push and pull dual fan system, COOLER MASTER Hyper 212 heatpipe direct contact.
a c 86 K Overclocking
March 28, 2010 11:29:15 PM

Andor. Your not supposed to thin the paste. Just clean off the old stuff, put the blob back on and put the heatsink on. The pressure will spread the paste just fine.

April 2, 2010 8:15:43 AM

@ Conumdrum: From what I've read, there are 2 ways of applying the thermal paste, either the one you've suggested or spreading the thermal paste thinly with a hard plastic like SIM card or piece of credit card.

Are there any tests to show the differences, or am I going to have to perform a test and see if there will be any results (and this time I'll be using Arctic Silver paste)?
!