Intel E8400 running hot

C

cjv98

n00b
Joined
Nov 24, 2010
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Hi everyone. I have an Intel E8400 with a Thermalright SI-128 cooler (big heatsink with a 120mm fan), and it seems to be running hot. I'm getting around 40-45c at idle, and 55-60c under load. Seems hot to me for a stock CPU that uses such a huge heat sink and fan. I've had this PC for just under 3 years, and this is the first time that I've actually paid any attention to the CPU temp. (I've been debating overclocking it, but if it's running this hot already, I don't want to push it any further.) The mobo temp reads right around 40-45C at idle too.

I know the 45nm CPU's can supposedly read temps incorrectly, but I don't think that's the case here. I've checked it using Speedfan, RealTemp, and through the BIOS on boot-up (only at idle for the BIOS, obviously), and it reads consistently hot on all of them. So unless there's a problem with the temp sensor itself, I don't think this is the problem. But I could be wrong.

My case doesn't have the best airflow. It's a Thermaltake DH101 HTPC-style case, so the mobo is mounted flat in the case, instead of standing up like they do in a normal PC case. Case has one 120mm fan at the front behind the LCD display for intake, and two 60mm fans above the mobo's I/O panel for exhaust. So maybe that's contributing somewhat. Come to think of it, I should double check the fans and make sure they're blowing the right ways - that would be a stupid mistake to make, lol.

Plus the mobo (ASUS P5E Deluxe) has some pretty significant heatsinks around the CPU for the chipset, so those probably aren't helping matters any. My RAM (OCZ ReaperX) has big heatsinks too, so there's definitely a lot of hot air around the CPU.

Also, I've noticed I can jiggle the heat sink and it will move - not sure if that's normal or not. Like, I can rotate the heat sink a little if I grab and try to twist it - I discovered this by accident when I was connecting a fan connector to the mobo, and the heat sink moved as I was trying to push the connector on. The heat sink was a major pain to mount, but I'm relatively certain that it is installed correctly.

In the BIOS, I noticed that it was initially set to try and keep the temps around 40C (using ASUS's "Q-fan" fan speed control). I dropped this down to 34C, the lowest possible option, and my temps are still reading right around 40C at idle. (So maybe there is an issue with the temp readings after all???)

Anyway, any thoughts on what's going on? Seems like either:
a) The temps are being read incorrectly (seems odd to me that the CPU would read 40C in the BIOS immediately on booting up. But then the mobo would be reading incorrectly too, since I'd expect them to both read about the same temp)
b) My heatsink isn't making good contact with the CPU
c) I have poor airflow (either due to the design of the case, or fans being installed
backwards, or some other factor I've overlooked)
d) maybe there's some other possible cause I've missed

Here are the products I'm using:
Case
Heatsink
mobo
 
As many here will suggest - reseat the heatsink. Make sure you only apply a tiny bb sized amount of thermal paste.
 
For what it's worth, my e8400 would idle at 42C with loads in the 50's C no matter what cooler I used.
 
Thanks for the replies so far. I'm going to try re-mounting the heatsink as soon as I get my AS-5 back from a friend.

I don't think I mentioned in my first post, that I have ASUS's "Q-fan" fan speed controls set to "optimal" (as opposed to "performance" or "silent"). I'm going to play with that tonight and see how that changes things. I may even disable Q-fan altogether and see how that affects my temps. As it is now, my CPU fan is inaudible. I know when the CPU fan gets the full 12V, it should be around 1200rpm (Scythe S-flex SFF21E 120mm), but I don't remember what RPM it usually runs at. I'm thinking the Q-fan might not be running it at full RPM until it starts getting pretty hot.

Just did the RealTemp/Prime95 temp sensor test; here's the results. (Everything looks functional to me). Tmax is set to the default of 100C, so that means the temps started around 60c and tapered down to 45-50-ish.

E8400Sensortemptest.jpg
 
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Update: I checked last night, and the CPU fan is running at max rpm (~1270), so that's a good sign. I changed the ASUS Q-Fan to "performance" mode instead of "optimal". Now my core temps are ~37C and 42C for each core respectively - maybe a degree lower than before, but about the same. (Ambient temp is 25-26C.) I also blew the dust out of the case,and double checked all my fans to make sure they were facing the right way (everything is fine there).

My case's intake fan is still only running at ~680rpm's (roughly 50% speed), and turning Q-fan off didn't make an immediate difference there, at least according to the BIOS. Maybe I need to save the changes and re-boot for them to take effect though.

I'm thinking it might be worth upgrading the fans if re-mounting the heat sink doesn't help. (I'm going to try that tonight and see how it goes.) I haven't looked into case fans since I bought this computer 3 years ago, and now it seems like all the manufacturers have changed their fan lineups, so I don't know what the "go-to" good fans are any more.

Does anyone have any recommendations for 60mm and 120mm fans that have good airflow but aren't insanely loud? I currently have two 120mm 1200rpm Scythe S-Flex fans (SFF21E, the "medium speed" version) for the CPU, and chassis intake, along with two 60mm Papst fans (Type 612 NGMI) which are controlled by built-in thermistors, and are starting to get noisy. I know 60mm fans are noisy regardless of which ones you get; I'm just looking for some of the better-performing ones. And I'd be looking for something higher-speed than the 120mm Scythes I have now - their "F" high-speed version of my fan would be good, except it's hard to find and probably outdated by now. I was reading a review of my CPU heatsink, and it said a higher-RPM fan may be needed to get enough airflow between the tightly-packed fins.
 
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Re-mounted the heat sink, and I'm getting exactly the same as before (34/42C at idle - I got that last night as well). A couple degrees lower than when I started all this, so it wasn't a total loss.

Arctic Silver's website says the temps may drop by 1-5 degrees as the paste breaks in over the first 200 hours of normal use; not sure how much I believe that; we'll see.

I realized one potential problem: my heatsink is the SI-128SE. The SE version has a mounting surface that's slightly convex - for whatever reason it isn't perfectly flat. (I actually found that out in a review, and I looked at mine, and sure enough, mine isn't flat). So it isn't making perfect contact with the CPU, which could be the problem..

If I really wanted, I could try to sand it smooth; but I'd probably sand through the nickel plating and expose the copper underneath. Not a huge deal, but I can't decide if it's worth the effort to get maybe an extra couple of degrees' worth of cooling.
 
Intel cpus are nortoriously concave. Sand both of them flat using well known lapping processes. Cpu heat spreaders are about half a cm thick, dont worry about "sanding through" I can take pics to prove if you need as I deihs'd a few in my years. Just please dont sand dry or without using a flat surface
 
IMG_1237.JPG

IMG_0749.JPG


note the sand marks on the 'ES' that was only sanded until it was flat, not all the way through the nickel

you dont see them in the pictures but i've also got an E8400, its been retired to 'server duty'
still runs to this day, almost 4 years later when i was running it at 4.5 ghz, 533 bus (as in 2132 fsb) 24/7 ;) E8400's are killer cpus. its at stock now so i cannot tell you the settings, and of course that was on water
 
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Thanks for the posts ryuji. Those pictures are really helpful. I'm debating lapping the heat sink at least a little. Might be a good project for a boring weekend. Not sure if I feel like messing with the processor or not; I'll have to read up on that some more.

What grit sandpaper do you use? An article I read said 600 grit, but I wonder if following that with something finer would do any good. With my heat sink, I'll probably want to start with something more coarse - it's visibly convex, so I'll need to remove a fair bit of material to get it flat.

Honestly though, for now at least, my graphics card is probably my bottleneck (HD 5770), and unfortunately I bought it less than a year ago, so I don't feel like replacing it. I'm going to try overclocking the gfx card a little and see where that gets me.
 
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I use 240 all the way to 2000 grit, but 1000 should be plenty good. Make sure you do it wet
 
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