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VRM Advice for AMD mATX fx-8120

post #1 of 17
Thread Starter 
This is the first PC I've built in a few years, so I have an Asrock 960GM/U3S3 FX that I've had about 2 weeks now. It has a fx-8120 running stock, with stock HSF.

I have noticed that after a few minutes Prime95 on all 8 'half cores' , the cpu will throttle back. (To be fair, it was over 85'F in the house: good california heat!)

I suspected VRM overheating. I kept stock speed, reduced voltage to 1.2, and put a fan directly over the mosfets. Throttling reduced, and I think it might even be gone completely.

I did some research, and read many things that I wished I came across before I bought the board. When I last build a PC, cpus took <80 watts, nobody worried about mosfets exploding, and even my cheapo MSI and ECS boards from back then are still fully operational; they are just pathetically slow compared to the new stuff.

I emailed ASRock support, and they said the board really can handle 125W, and that the board will throttle back if the VRMs overheat, and that putting a fan on the mosfet was the correct option. The board seems 3+1 though, it's got 4 pairs of transistors, and 4 chokes by the CPU, and then 1 other choke & transistor set near the RAM.

Should I believe them? If I go and put heatsinks on the mosfets, and point a fan on them, should I believe a fx 8120 stock (or fx-8120 at fx-8150 speed) should be 'safe?' Of course I won't run prime95 24 hours a day, but when I do hit those moments in peak load (video encoding, games, etc), I don't want to let the magic smoke out of the transistors. I suppose throttling is better than exploding!

I did a little further research: I looked up the part number for the transistor/gate driver pairs on the board, and each device is rated for 50 watts. So I'm thinking 50 watts x 3 = 150 watts, so a 125 watt processor at stock, with cooling should be 'fine'. Is 25 W headroom 'good enough'? I have no idea what the effecency of the whole VRM system is though: If the vrm components are getting warm, they are dissipating heat/energy, so a CPU pulling 125 watts will need >125 watts through the transistors. If

I read through some additional items on this forum, and even the 4+1 phase ASUS M5A88-M which claims 140W has trouble feeding the 8150 stock power requirements. I also hear sometimes you get an ASUS board with out-of-date BIOS, and you need to immediately RMA it so they can reflash it to recognize your FX chip.

What would you do in my situation?

1. Keep the existing board, add heatsinks, fan directly on vrm, keep at stock. And get a better CPU cooler.

2. RMA the board, pay newegg's restocking fee and get something else. (And what's the something else?) I would like to keep sata3 usb3 if possible.


Thanks!
post #2 of 17
Given that the throttling feature is present, nothing is "unsafe". However, you may not get full reliability with this setup. With FX-8XXX I usually recommend 6+2-8+2 phase power if you are thinking of making real use of the processor. They are very, very power intensive.

The ratings you found are useless unless they are defined at a specific temperature. The 50W rating could be a rating at 25C. That means at a load temp of 60C.... you get the point. The capacity is reduced. Experience is a good estimator of what phase count is enough and in the experiences of many users, a 125W TDP Phenom II x4 or x6 processor requires the capacity of at least 4+1 phase VRM for reliable operation at stock speed. An FX-8XXX is even more intensive than that. Select 3+1 phase VRMs have been ratified to work by the manufacturer but have not been through the best experiences with users. You can see my VRM failure/incident database for more info. Lately I've also started recording non-failure incidents which include throttling.

Given you encode video which can consume lots of CPU for long periods of time, I recommend that you make an investment towards more reliable hardware if you really value your reliability. You may otherwise be losing performance without noticing.
post #3 of 17
Quote:
Originally Posted by xd_1771 View Post

Given that the throttling feature is present, nothing is "unsafe". However, you may not get full reliability with this setup. With FX-8XXX I usually recommend 6+2-8+2 phase power if you are thinking of making real use of the processor. They are very, very power intensive.
The ratings you found are useless unless they are defined at a specific temperature. The 50W rating could be a rating at 25C. That means at a load temp of 60C.... you get the point. The capacity is reduced. Experience is a good estimator of what phase count is enough and in the experiences of many users, a 125W TDP Phenom II x4 or x6 processor requires the capacity of at least 4+1 phase VRM for reliable operation at stock speed. An FX-8XXX is even more intensive than that. Select 3+1 phase VRMs have been ratified to work by the manufacturer but have not been through the best experiences with users. You can see my VRM failure/incident database for more info. Lately I've also started recording non-failure incidents which include throttling.
Given you encode video which can consume lots of CPU for long periods of time, I recommend that you make an investment towards more reliable hardware if you really value your reliability. You may otherwise be losing performance without noticing.
Well sir there are some good 4+1 and 4+2 mobo out there that can handle a FX-8120 or FX-8150 at stock or with a mild oc on it. But you need to know which mobo has good 4+1/4+2 phase power.
post #4 of 17
Thread Starter 
I was running this board in a small case (Silverstone SG02) with the stock cooler. Today I installed a Corsair H60 to try to get some of the heat out of the case. I currently have the radiator external, outside the back of the case. Everything inside the case is much cooler, and I have a small fan blowing down onto the VRM mosfets. The fan I'm using for the vrms is actually just a fan taken off some old CPU heatsink I had laying around.

I no longer have any throttling issues at stock speed. (3.1 Ghz) I ran prime95 on 8 threads for over an hour. The cpu stayed under 50C the entire time.

I tried enabling Turbo Core, but the motherboard jacks the voltage up to 1.4, and then it immediately starts throttling.

So I started messing about manaully. I can run at 3.4Ghz at 1.25 V with no throttle. At 1.3V, it does start throttling. I'm also not sure if 1.25V at 3.4 Ghz is stable, I need to run it like that for a while. For some reason 1.25V sounds low. If this proves stable, I'll let turbo core take it up to that. Then I'll turn cool and quiet back on, and 90% of the time the computer is on, it'll just be cruising around at the 7x multiplier waiting for me to click on something smile.gif

I also ordered some mosfet heatsinks from newegg (The small Enzotech C1's) to make things a little cooler down the road. To be safe, I won't be using the heatsinks to attempt on overclock, it'll just to really make sure the magic smoke stays in the part! I am also going to put another small fan blowing cold air in the RAM area, since there is a VRM module there that looks like it relied on the CPU cooler to blow on.

So, if there's room in the VRM database for it, mark the ASRock 960GM.U3S3 FX down as having the FX-8120 stock speed being the absolute maximum it can handle without throttling, and that's with aggressive cooling. ASRock claims a 8150 will work, I see no way it ever could at 100% load. Maybe in games that only run a couple threads, it can handle a 8150 at turbo core speed. But when you're doing that, it's just really a 4100, and I bet a fx-4100 runs at relatively high clocks on this board just fine.
post #5 of 17
You should save your money towards a new board rather than investing in MOSFET heatsinks. If the capacity is an issue that isn't being solved by your current cooling (and active VRM cooling is already itself more effective than heatsinks, meaning you'll get little more heat loss) then it will never be solved. The only way to get your headroom unlocked is a new board.
post #6 of 17
Thread Starter 
I'm not unhappy with a stock-clock FX-8120. Actually 3.4 ghz isn't 'stock', that's the default turbo-core speed, and I can sustain that for over an hour without any throttling. I turned cool and quiet back on, so now everything scales properly from 1.4ghz to 3.4 depending on load. Prime95 can ran over an hour at 3.4ghz on 8 cores, and nothing breaks or throttles. My computer won't be pushed this far for extended periods of time, so now that I'm done experimenting, I'll leave my computer alone and let the test of time determine if it'll explode.

Usually I don't overclock; but this forum appears the best 'authority' on the net about what these motherboards can and can't handle; you know even more than the manufacturer. I tried a my 8120 at 3.6 ghz ( ==FX-8150 ) , and it throttles; every 10 seconds or so the chip drops to 1.4 ghz for 1 second and then clocks back up to 3.6. But, the manufacturer probably assumes prime95 24/7 is not what most people would do; A fx-8150 running at stock speed with default turbo core settings probably runs 'fine' for the casual observer. Even a game that takes up 2 or 4 threads at turbo core speeds would leave half the chip mostly idle, making for no, or very little throttling. Other short tasks, like file compression, might use multiple cores at 100% for a few seconds at a time, before anything starts throttling, so the computer seems fast. Does it work? I guess so. Is it sneaky and dirty to label a board 8-core capable when it barely makes the cut? YES! Not as dirty as MSI, at least this board will keep itself from exploding.

If the test of time shows a stability issue with my current settings, I will have to replace the board with something more capable, like one of the GIGABYTE boards. What is keeping me from doing that at the moment, is all the ones I see for sale lack either ddr 1600 or sata iii or usb 3.0. Finding all 3 for micro atx am3+, and 4+1 setup, seems difficult. There is the ASUS M5A88M which seems to have everything my board has + a good 4+1 power setup, but I am detracted by 2 things 1) some don't ship with the latest BIOS and you need to instantly RMA unless you have an old chip around and 2) Reports of throttling on 8 core CPUs. Yes, my current board also throttles on 8 cores, but I'm not going to buy another board with the same problem, AND and I already tackled my throttling issues to my satisfaction.
post #7 of 17
the tooth
(18 items)
 
HAF 922
(12 items)
 
902
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CPUMotherboardGraphicsRAM
fx 6300 asus m5a97 asus gtx 570  8gb 1600mhz gskill ripjaws 
Hard DriveOptical DriveCoolingOS
1.5 TB seagate 7200 lg blueray coolermaster hyper 212 evo windows 7 home premium 
MonitorPowerCaseAudio
50 inch 3d plasma 1080p,,smart tv coolermaster 700 watt coolermaster 922 denon 7.1,home theatre 
CPUMotherboardGraphicsRAM
amd 965x4 asus,m4n72-e asus 5770 cucore 4gb 1066 gskill ddr2 
Hard DriveOptical DriveCoolingMonitor
seagate 500gb lg cheap zalman something cpu cooler??,,,works pretty good lg 22 inch 
PowerCase
xeon 600 watt antec 902 
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the tooth
(18 items)
 
HAF 922
(12 items)
 
902
(11 items)
 
CPUMotherboardGraphicsRAM
fx 6300 asus m5a97 asus gtx 570  8gb 1600mhz gskill ripjaws 
Hard DriveOptical DriveCoolingOS
1.5 TB seagate 7200 lg blueray coolermaster hyper 212 evo windows 7 home premium 
MonitorPowerCaseAudio
50 inch 3d plasma 1080p,,smart tv coolermaster 700 watt coolermaster 922 denon 7.1,home theatre 
CPUMotherboardGraphicsRAM
amd 965x4 asus,m4n72-e asus 5770 cucore 4gb 1066 gskill ddr2 
Hard DriveOptical DriveCoolingMonitor
seagate 500gb lg cheap zalman something cpu cooler??,,,works pretty good lg 22 inch 
PowerCase
xeon 600 watt antec 902 
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post #8 of 17
Thread Starter 
Well, I learned my lesson. It blew up. While mostly idle! It was time to reboot linux, so I when I selected 'reboot', the machine turned off instead, and I could not get it back on. The only thing 'weird' I did, was I just using the sata iii port for the first time in LInux (I had installed drivers for it). Maybe, just maybe the open source driver made the chip do something bad and it took the whole motherboard down, but I doubt that. And if you can kill the whole board with a tiny piece of malfunctioning software, I don't want that board anyway.

Tried clear cmos, tried removing sata devices, one ram module at a time, removed add-on pcie video card. No dice. H60 seems to still pump ok. Tested power supply and video card with an old motherboard, no problem with those. I RMA'ed mobo as defective to newegg. For refund, I don't want another one of these heaps.

I'm in an annoying situation:

Can't test cpu: no other am3/ 3+ board. I'm stuck with the CPU, if it got toasted I can RMA for replacement. (No refunds offered on CPUs)
Can't test ram: no other ddr3 boards (lame, i know, my newest other desktop is DDR1 ! (Yeah, I've been out of the desktop game and using laptops too long!)

So I guess I'm the the market for a new AM3+ motherboard. This time I'm armed with the VRM info database on this site. (Thanks, xd_1771 and reflex99)

I can go with another microatx OR I can go to full ATX. I know full ATX will give better support, and I know it's probably the right choice, but I'm a little miffed because I got this microatx case new just for this build, and the best refund Amazon will offer for it is 50%, so I might as well keep it. So I need a QUALITY micro ATX board OR an ATX case and micro ATX board.

The ASRock 960GM U3S3 FX is complete garbage.
post #9 of 17

oops
the tooth
(18 items)
 
HAF 922
(12 items)
 
902
(11 items)
 
CPUMotherboardGraphicsRAM
fx 6300 asus m5a97 asus gtx 570  8gb 1600mhz gskill ripjaws 
Hard DriveOptical DriveCoolingOS
1.5 TB seagate 7200 lg blueray coolermaster hyper 212 evo windows 7 home premium 
MonitorPowerCaseAudio
50 inch 3d plasma 1080p,,smart tv coolermaster 700 watt coolermaster 922 denon 7.1,home theatre 
CPUMotherboardGraphicsRAM
amd 965x4 asus,m4n72-e asus 5770 cucore 4gb 1066 gskill ddr2 
Hard DriveOptical DriveCoolingMonitor
seagate 500gb lg cheap zalman something cpu cooler??,,,works pretty good lg 22 inch 
PowerCase
xeon 600 watt antec 902 
  hide details  
Reply
the tooth
(18 items)
 
HAF 922
(12 items)
 
902
(11 items)
 
CPUMotherboardGraphicsRAM
fx 6300 asus m5a97 asus gtx 570  8gb 1600mhz gskill ripjaws 
Hard DriveOptical DriveCoolingOS
1.5 TB seagate 7200 lg blueray coolermaster hyper 212 evo windows 7 home premium 
MonitorPowerCaseAudio
50 inch 3d plasma 1080p,,smart tv coolermaster 700 watt coolermaster 922 denon 7.1,home theatre 
CPUMotherboardGraphicsRAM
amd 965x4 asus,m4n72-e asus 5770 cucore 4gb 1066 gskill ddr2 
Hard DriveOptical DriveCoolingMonitor
seagate 500gb lg cheap zalman something cpu cooler??,,,works pretty good lg 22 inch 
PowerCase
xeon 600 watt antec 902 
  hide details  
Reply
post #10 of 17
Thread Starter 
That's a nice picture!
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