Motherboard northbridge reaches 120c (!) and dies

wumpus

Last week I built up a new Core 2 Duo system:

- Asus P5B Deluxe (965 express) motherboard
- Core Duo 2 E6600
- Scythe Infinity
- 2GB AData DDR2 667 RAM

And it was working great; it burned in at 3.1 GHz no problem, with dual instance of Prime95 running for hours. As the system was burning in with dual prime95s, I checked a few temperatures with my temperature gun. I noticed that the northbridge was quite hot at around 70c. And that's with an open case. I've seen northbridges run hot before, and I figured that was the peak temp, so I wasn't particularly worried.

Note that the P5B Deluxe has a nifty heatpipe on the p965 express northbridge. Which is supposed to keep it at reasonable temperatures.. right?

Well, I bumped up the FSB a little bit more today (to 3.2 GHz, really a modest increase) and I was doing some more dual prime95 burn-in. As I was using the computer, it all of a sudden shut down-- and I smelled a tiny hint of "burning electronics" smell. That ain't good! Note that the case was open at the time, so airflow was not an issue. I took out my temperature gun and checked the northbridge-- 120 degrees celcius! Holy crap!

The motherboard will no longer boot, and I assume it's because the northbridge is toast. As long as I've been building CPUs (since 1995 or so) I've never had anything quite this catastrophic happen. So I have some questions:

1) What the heck did I do to cause this? Clearly the heatsink/heatpipe used to work, because I was reaching 70c under load only a few days ago (again, with the case open while testing). The only things that changed were the FSB increase along with a modest memory voltage bump, and I swapped around the primary and secondary video cards (X300 for 3rd display, X1900XTX for 1st and 2nd). That's it. Prior to this I was using the system for a few days, playing games, surfing the web, etcetera.

2) Why didn't the northbridge shut itself down (or crash) before it reached 120c? Do northbridges lack the kind of temperature control seen in modern CPUs?

Any advice greatly appreciated.

In the meantime, I'm returning this board for a refund, as defective (although newegg still charges me $30.. sigh), and I ordered a replacement.

kentc

Bluefront · Posted: Mon Oct 09, 2006 2:09 am Post subject:

Sad story......proves that temperatures do mean something, even with supposedly components designed for heat. Perhaps the chip contact with the heatsink loosened somehow, or maybe the heatpipe failed (leaked).

NB temps have always concerned me.....some of my Intel boards register in the 70s, and I always rig a better airflow for those setups. I suspect a defective product in your situation though. If such a thing was common, we'd hear of many examples of this type of failure. Too bad.....
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silon · Joined: 27 Jun 2006 Posts: 46

could this be caused by a lack of airflow over the NB/VRM heatsinks? perhaps they were designed for HSFs that blow all over the mobo?

jaganath · Joined: 20 Sep 2005 Posts: 5085 Location: UK

wumpus · Posted: Mon Oct 09, 2006 5:55 am Post subject:

I'm wondering if something about having the X300 video card in the first PCI x16 slot caused some kind of extra load on the northbridge. Normally the X1900XTX is in that first slot, but I was having a problem where the motherboard would only detect the card in the second PCI x16 slot, so I switched them around.

But man.. my eyes nearly popped out of my head when I pointed the temp gun at the northbridge and saw it read 120 degrees C! I've never even recorded a temp over 80 C, or even 90 C, anywhere on any computer before.

I'm inclined to think the heatpipe and heatsink were doing their jobs, otherwise I wouldn't have seen the heatsink part get to 120c -- right?

I still don't get it. Why all of a sudden when I made so few changes and it was doing 70c under load the day before? Maybe you're right -- perhaps the northbridge was just plain defective.

autoboy · Posted: Mon Oct 09, 2006 7:55 am Post subject:

You have a board with heatpipes running from VRM to the northbridge.

The 965 chipset is a cool running 90nm chipset that does not require any cooling other than a passive heatsink. However, the trend right now is to connect the VRM and the northbridge for some perverted reason. Customers think this helps cool the northbridge and it makes for a great marketing ploy. However, in reality the northbridge runs cooler than the VRM, especially when overclocking.

Think about it like this: If the cpu is using 100W when overclocked, and the VRM is 85% efficient, then the VRM is dissipating 15W of heat while the northbridge is using 10W. Total on the heatsink is 25W. Heat moves from the VRM to the northbridge over the heatpipe, warming up the northbrigde instead of cooling it. A crappy design IMO. The VRM cooling fins are designed to be cooled by the cpu air but you had no air moving around them. As the VRM got hotter, it got less effiecient and eventually went into thermal runaway causing the northbridge to die or part of the power circuitry.

Normally this does not happen to the extent that it did on your board. I'm gonna guess that something was wrong with the VRM on your board that caused it to have crappy efficiency, maybe 70%, which would dump 40W onto the northbrigde and the puny heatsinks at the end of the heatpipe.

The whole cooling design is dumb. The VRM can withstand much higher temperatures than the northbridge. There is no reason to tie them together thermally. It gets even worse when they tie the southbridge into the system. Many southbridges don't even need a heatsink let alone a huge, expensive heatpipe run to the VRM. All it is doing is heating up the southbridge.

Take the board back. Get a new one and try measuring the difference in heat on the VRM to northbridge. If the northbridge is hotter, then I am wrong. Otherwise, it would make sense to re-engineer the cooling system with a Zalman on the northbridge, and some simple extruded heatsinks on the VRM.

wumpus · Posted: Wed Oct 11, 2006 5:08 pm Post subject:

Well, I got my new P5B and I'm up and running again with a mobo replacement. Memory, CPU, etc are all the same.

This time, I took off the NB and SB heatsinks and cleaned off the crappy TIM material underneath, and applied some Ceramique compound instead (well, except where the heatsink covers the VRM stuff, as autoboy pointed out; that area uses thermal tape) What's up with manufacturers using crappy TIM pads from the factory? Is it really so hard to put a dab of heatsink compound on there?

Currently running at stock speeds, but I'll be paying MUCH CLOSER attention to NB temps this time around as I overclock Razz

Chocolinx · Joined: 19 Jan 2006 Posts: 311 Location: Toronto

I have the same board. O.O Should I remove the cap on the heatsink? I never know how hot that thing is because SpeedFan can't detect it, and BIOS doesn't have any temps for it either <.< I have no Temperature gun or what-not.

Do we do the same thing everyone else has been doing with the P5W DH boards?

wumpus · Posted: Wed Oct 11, 2006 5:58 pm Post subject:

Ok, so everything is set back to the way it was, with the exception of the northbridge voltage.

Northbridge is set to "auto" instead of 1.55v; memory is set to 2.25v, CPU is set to 1.4625v, and the FSB is set to 355 * 9 or 3.2 GHz.

Right now Dual Prime95 has been burning in for about 15 minutes or so. Raytek Raynger ST temp gun sez.. (all measured on top. All 6 laser points were on the target in the center as near as I could get it)

Northbridge
75 c

Southbridge
72 c

VRM heatsink
56 c

CPU (measured from side; there's no good angle to shoot the Scythe Infinity with a temperature gun)
35 c

Note that I did clean each one of these heatsinks and remount them with AS Ceramique paste underneath. So the temps might be a little higher than they would have been on the old, fried mobo with the default crappy TIM.

The CPU heatsink is clearly massive overkill. I touched the solid aluminum at the very bottom, the part closest to the CPU, and it's BARELY WARM!

I'm now thinking I might have fried the northbridge by using so much overvolting on it (1.55v) when clearly it doesn't need any.. I think the default "Auto" voltage for the 965 express NB is 1.25v?

This case has decent airflow. It's the Lian-li V2000 with 120mm exhaust fan, which I tin-snipped into a huge, free flowing area.

wumpus · Posted: Wed Oct 11, 2006 6:03 pm Post subject:

Chocolinx · Joined: 19 Jan 2006 Posts: 311 Location: Toronto

wumpus · Posted: Wed Oct 11, 2006 6:31 pm Post subject:

Ah, I see. That does make sense. The decorative cap on the northbridge probably does reduce airflow somewhat and retains heat.. I'll give that a shot in a sec.

wumpus · Posted: Wed Oct 11, 2006 7:58 pm Post subject:

Hmm. I removed the northbridge cap (really a metallic sticker) and it's hard to tell if the results are any better. I can't get a solid reading off the fins using the temperature gun.

It seems to make sense that the NB would do better without the cap-- it exposes the fins more and allows more convection around the fins. I'd probably recommend it as a mod because it's easy and sensible, but the temp gun results (and Mark I finger results) were inconclusive. The P5B northbridge still gets blisteringly hot under load, with the cap or without it.

wumpus · Posted: Sat Oct 14, 2006 6:52 pm Post subject:

I decided that I was unhappy with the temps I'm getting on the p5b northbridge (always unpleasant to touch, and nearly burning when under load-- eg, 80+c). Even with the cap removed. I went ahead and ordered one of the Thermalright HR-05 northbridge coolers.

Like I said, this is disappointing given that I have good airflow and it's a fancy heatsink/heatpipe arrangement already on the p5b deluxe.

It's gonna be a VERY tight fit with the 125mm wide Infinity on there..

.. but I think it will work, just barely. They might end up touching a little, but so what.

This pic from a SPCR review shows the Ninja which is 110mm; it seems that there's a bit of space there for the extra 15mm of the Infinity (well, 7.5mm on each side).

It's a crazy world we live in where the latest overclocked CPUs barely get warm under load, yet the NB and SB regularly get to 80c in a well ventilated case. Sigh..

cmthomson · Joined: 09 Oct 2005 Posts: 1108 Location: Pleasanton, CA

Ingenuous question time: did you disable Hyper Path 3?

On a P5W DH, this "feature" overclocks the north bridge by strapping it to 800 instead of 1066. This gives a performance boost at stock frequencies, but seriously overheats the north bridge at faster FSB frequencies.
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Chocolinx · Joined: 19 Jan 2006 Posts: 311 Location: Toronto

cmthomson · Joined: 09 Oct 2005 Posts: 1108 Location: Pleasanton, CA

Well I checked the manual (online), and it appears that the P5B does not suffer from this feature after all.
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IceFire · Posted: Mon Oct 16, 2006 4:35 am Post subject:

I don't know about the rest of you, but for my case, open is actually worst for temps. I just built a C2D 6300 with a P180B and GigaByte G965-DS3 board. My NB gets very hot - way too hot to touch. I had a clearance problem since I use a Sythic (Infinity - I think the Nija is a better cooler). I use a Zalman NB2 on it turned sideway with a hood around the Infinity and the NB. This also cools the components around the CPU. This is just with the rear case fan and no CPU fan.

I also found that I have to place a 3 rd fan in the middle drive area to cool the SB. I figure this isn't going to be a big deal since I will be going away from the built-in graphics. This didn't add any noticable noise to the system since the fan is in the middle of the case and set to low.

I notice a lot of people that use the Ninja don't cool the components around the CPU too well or not at all. This is getting to be a big problem since NB and SB are get in the high temp area and the VRM are getting hotter also.

My goal is to do something like wumpus in terms of sectioning off everything. I will put some HS on the VRM, do a more permanent hood instead of cheap quick cardboard, divide the CPU section off from the graphics card area and place a filter/opening in the front.

Mats · Joined: 26 Dec 2003 Posts: 2552 Location: Sweden

wumpus: Since you're using a chipset that raises NB speed when lowering multiplier I must ask the obvious question: Did you keep the original multiplier (x9) while overclocking?

wumpus · Posted: Mon Oct 16, 2006 3:47 pm Post subject:

Yep, default multiplier.. no adjustment to multiplier at all; I just raised the bus speed to 355.

There's plenty of airflow in this case. The 120mm exhaust fan is running at a good clip directly behind the CPU, and as you can see from the pics, the CPU and northbridge are neighbors..

Chocolinx · Joined: 19 Jan 2006 Posts: 311 Location: Toronto

This thread is really scaring me lol. I don't want my P5B to blow up on me either! lol.

If I decide to get a NB cooler how would I go about cooling the VRMs? Since the stock heatsink would be completly taken off. Would that supplied fan that came with our P5B-Deluxe be of any help?

zjohnr · Joined: 22 Oct 2006 Posts: 2 Location: upstate NY state

Mari0-Br0s · Joined: 23 Jul 2005 Posts: 138 Location: Montréal, Québec

WHAT!!!! 80C on an Intel NB!!! I'm glad to be completly sold to nVidia!
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wumpus · Posted: Sun Oct 22, 2006 6:44 pm Post subject:

I haven't gotten the HR-05 yet. It's scheduled to arrive today.

I did have several heat-related crashes yesterday. It was unseasonably warm and I was playing Battlefield 2142-- not a good combo! I strongly suspect the northbridge, as usual, since the CPU barely gets warm and the system is rock stable under dual Prime95s.

As a temporary fix I removed the fan from the Scythe Infinity, and propped it at an angle in the case so it blows air across the CPU and the existing Asus P5B northbridge heatsink. This made a huge difference.. now I can actually touch the edge of the northbridge and hold my finger there. And I can play Battlefield 2142 for extended periods without the system freezing, which is a plus..

I'm definitely looking forward to getting the HR-05. I don't know why I'm having such severe heat problems with the existing NB cooling system on the P5B Deluxe. Maybe my case has a lot less airflow than I thought.. I have no idea!

wumpus · Posted: Mon Oct 23, 2006 8:31 pm Post subject:

It fits! Barely.. but we knew it would be close.

Also, MASSIVE improvement in temperatures! With only the rear case fan going, the HR-05 does get quite toasty under load-- slightly uncomfortable to touch. I set up the low-rpm scythe fan, with Zalman fanmate reducer, so that it blows across both the CPU and the NB heatsinks. Now it's barely even warm.

I think some of the earlier posters diagnosed this correctly.. the problem with Ninja/Infinity type coolers is that they provide no direct or indirect airflow over the northbridge.

The 965 northbridge dissipates ~20w under load, probably more with overclocking. That's approaching the levels of a Pentium II 450. The 965 northbridge, at least when overclocked, requires some direct airflow to cool properly. IMO.

But I did blow up one motherboard with 120c NB temps to prove my point Sad

Chocolinx · Joined: 19 Jan 2006 Posts: 311 Location: Toronto

Looks very nice! I want to do that! But my computer is so settled in Sad

I don't want to take it apart.

Hey and SpeedFan 4.31 now reads P5B sensors! Hurry up and download it! Oh and I check this temp on SpeedFan. WTF is AUX Temp? It's 127ºC on my board! That's not the northbridge like yours is it?

EsaT · Posted: Mon Oct 23, 2006 10:01 pm Post subject:

wumpus, did you check what kind thermal paste there was under northbridge heatsink when changing it?

In P5W DH that thermal "paste" is something very crappy... and then there's way too thick layer of it in northbridge heatsink despite of heat transferring area being so small (bare die) and good contact being crucial.
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orihara · Joined: 23 Oct 2006 Posts: 27

This almost makes me wonder if it would be a good idea to stick the squirrel cage fan onto the VRM heatsink, even though it says not to unless using a passive heatsink or watercooling.

geforce1 · Posted: Tue Oct 24, 2006 10:09 am Post subject: