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(overclocking) AMD FX-8120 on Asrock 990FX extreme 3

post #1 of 15
Thread Starter 
I was getting into overclocking my 8120 recently and I noticed my CPU was throttling even when it's only reaching 56-58c ,I did some googleing and found out that my VRMS were most probably overheating. So Today i decided to try and kinda just stuck a custom heat sink on the 5 exposed VRM modules that I hand cut out of an old AMD heat sink.

chopped up heat sink
9C7V1.jpg

Before adding custom heat sinks
rw6V1.jpg

heat sinks on and runnin.
TRYZd.jpg

Here are my results.

The dips in the graphs represent the throttles any time there's a large voltage drop and cpu temperature drop that would be a throttle.

EfVyr.png

cdnAZ.png

As you can see The heat sinks did improve performance but not a breath taking amount frown.gif I know they were making good contact with the VRMs cause they were pretty hot to the touch. I'm hoping to make a more permanent setup by using sticky thermal pads on the bottom of my heat sink instead of thermal grease (cause it'll slide off) and maybe solder the extra coolers directly to the small cooler that already exists on my motherboard.

Any input is welcome, and if anyone knows where i could simply buy a vrm cooler designed for 4-1 stage vrms of this sort i would be very happy

If I bought this NB cooler could I just stick it on?
Edited by Burritomaster24 - 5/2/12 at 9:37pm

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post #2 of 15
well all i can say is get a asus sabertooth, i have same board and found out its not realy ideal for fx due to 4+1 vrm some people say try and overclock a fx with it and it might go boom!... tongue.gif
post #3 of 15
Thread Starter 
Hmm, yeah well it seems to throttle enough to keep its self alive, I'm not really in the market to buy another motherboard , but thanks for the quick reply.

EDIT: Hahaha funny thought here it appears that the mounting for the saber tooths vrm cooler is the same as my board. maybe i could special order one of them from asus.

tongue.gif wait no it isn't fail, it's much longer of a heat sink.
Edited by Burritomaster24 - 5/2/12 at 9:28pm
post #4 of 15
Attaching a heat sink to VRMs will not increase current carrying capacity of the MOSFETs to the CPU.

For example, Every Phenom II X6 125watt AMD AM3 CPU requires 110 Ampere current at default clocks for optimum performance continuously (According to AMD Power and Thermal Datasheet). And many 4+1 phase motherboards have died while overclocking with 125watt CPU (excluding those which have throttling function like most Asus/Asrock and some Gigabyte). Because each phase in a 4+1 design (4 phase for CPU core power and 1 phase for IMC or CPU-NB) can provide up to maximum theoretical current of 40 Ampere (this applies for almost all 4+1 phase motherboards). It means 40 Ampere x 4 Phase = 160 Ampere max (you should know that nothing is 100% efficient and when any of those phase are stressed to provide current close to max value say >30 Ampere from each phase, extreme heat occurs). In this situation Adding a heat sink/water block/LN2 can only make the VRM to become less hot. It doesn't mean that it will provide more current than it can offer. As we all know AMD 125watt FX CPU's power consumption is more than Phenom II (It means FX needs more current even at default clocks). And an Overclocked FX will surely exceed the max current support from 4+1phase. That is why it is throttled down to lower clocks to save the VRM from burning. All this theory means that 4+1 phase is not designed for continuously operation at optimum speed for all 125w CPU.

If you want to overclock without throttling and want to make your CPU stable for 24/7. I want you to buy any currently available 8+2 phase motherboard. I had killed two MSI 790FX GD70 and one MSI 890FXA GD70. They all were 4+1 phase (without throttling function) and they all died within 15 minutes in Prime95. And then I bought Gigabyte 8+2 phase motherboard, nothing damaged even >24hrs in Prime95.

If you want to know more about VRM, note the vendor/model no printed on your Extreme 3's VRM and search for datasheet and see if you could find one.

Some formulas:
1) To know the current requirement of CPU at load = CPU's Wattage at load / CPU's core voltage at load
(^followed by Power consumption = volts x amperes) (I know you know this smile.gif )

2) To know how much wattage is being pulled by CPU at load.
Power consumption = [ TDP x ( CPU frequency in MHz overclocked / CPU frequency in MHz default ) x ( CPU Vcore at OCed state / CPU Vcore at default state )^2 ]

Edited by sumitlian - 5/3/12 at 12:30pm
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post #5 of 15
Thread Starter 
Yes they are throttling not do to overloading but overheating ,it's only throttling every so often and when I had applied my rigged heat sinks to the VRMs they were much more stable, if you look at my charts.

I ran prime 95 last night at an OC of 3.6 at 1.3 volts and it never throttled once. I really don't want my mobo getting close to throttling so that's why I wanna cool the vrms. I'm going to buy this kit when my monitor rebate come in.

It says 4+1 supports cpu's up to 140 watts and I'm currently using. 162 with my oc according to your formula. and as long as my bios is driving my cpu with the voltage I actually set. i feel kinda less likely to overclock now. :C

wait I checked the other mobo with an 8+2 power phase and it says 140 watts also... I guess this is a base rating. even the 12+2 phase says 140.
Edited by Burritomaster24 - 5/3/12 at 7:36pm
post #6 of 15
hello,
i have a 99x mobo and not an fx mobo like i should have.the power phase is 6+2 for a 6 core cpu.my cpu socket temp is at 61c but my core temp is at 47c,i think its having the wrong power phase that is causing this problem and thus i cant clock high due to my socket temp. i hate hind sight mad.gif
    
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post #7 of 15
Thread Starter 
My socket temp has gone up to around 63 sometimes without throttling its not the cpu temp that will do it unless you have cool 'n' quiet turned on.
post #8 of 15
Um so did you put the heat sinks on the VRM, or the chokes? That may be the reason why there wasn't a drastic improvement.
Chokes are those bigger black boxes while I think the VRM is already under that stock heatsink.
Chokes act as filters, and while they do get hot and cooling may help, you might need to aim a fan at the existing heat sink. Anyway see how you go, hope it's good.
post #9 of 15
Quote:
Originally Posted by Burritomaster24 View Post

Yes they are throttling not do to overloading but overheating ,it's only throttling every so often and when I had applied my rigged heat sinks to the VRMs they were much more stable, if you look at my charts.
I ran prime 95 last night at an OC of 3.6 at 1.3 volts and it never throttled once. I really don't want my mobo getting close to throttling so that's why I wanna cool the vrms. I'm going to buy this kit when my monitor rebate come in.
It says 4+1 supports cpu's up to 140 watts and I'm currently using. 162 with my oc according to your formula. and as long as my bios is driving my cpu with the voltage I actually set. i feel kinda less likely to overclock now. :C
wait I checked the other mobo with an 8+2 power phase and it says 140 watts also... I guess this is a base rating. even the 12+2 phase says 140.

If your overclock really doesn't pull more than 162watts, then 162w / 1.3v = 124 Ampere
And 124 Ampere / 4 phase = 31 Ampere per phase. Which should be safe if you could make them cool.

This MOSFET specification is from my previous 4+1 phase motherboards ( MSI 790FX GD70 and MSI 890FXA GD70 ). MOSFET name is 'Renesas R2J20604'. Each MOSFET is capable of providing 40Ampere max.
495




And My new 8+2 phase 990FX UD5 has 'Vishay Siliconix SiC769' MOSFETs.

495


As you can clearly see that:
In 4+1 phase design,
Each MOSFET for CPU core can deliver 40 Ampere, and hence Total Current = 40 Ampere x 4 phase = 160 Amperes
Remaining one MOSFET is for CPU-NB/IMC and can deliver = 40 Ampere

In 8+2 phase design,
Each MOSFET for CPU core can deliver 35Ampere, hence total current = 35 Ampere x 8 Phase = 280 Amperes
And remaining two MOSFETs is for CPU-NB/IMC and can deliver = 70 Ampere

and 280 Ampere >> 160 Ampere
That is why I was suggesting you to buy a 8+2 board, bro smile.gif !

Take another example:
My Phenom II X6 at 4.004Ghz at 1.456v pulls 226watts at full load. (By the formula i've stated already)
since, Ampere requirement = Watts / Volts
Ampere requirement = 226 Watts / 1.456 volts = 155 Amperes

If you put this overclock in a 4+1 phase mobo where 4+1 phase can only deliver 160 Ampere max. This situation will heaten up the MOSFETs to >100c temp. Which is beyond the operational range. You will have to use chilled water cooling or LN2 near VRM area. Even if you manage this, stability can not be guarantied because nothing is 100% efficient. Either chokes will blow up or MOSFET will be bricked silently.
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post #10 of 15
Chuck another fan on that 212 and you'll get better results.
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