Temp difference between cores

[Jonathan Lemmens]

Hey guys,

 

I bought a second hand Intel Core2Quad Q9550 recently for my old "hobby PC". I noticed right away that one of the cores was much hotter than any of the others and the second is a little cooler than the rest.

Oddly enough this temp difference stayed the same (11-13 C) when I started overclocking. The pic below is under load at a slight 3.4GHz OC, voltage is't optimized yet. At idle temps are: 41 29 35 34

 

I re-applied thermal paste twice (slightly more the second time) and mounted the cooler in a few different positions, nothing seemed to change the temps. I've heard that CPU's from this generation had issues where the heatspreader is slightly bulged and might not make perfect contact with the cooler. Polishing or 'lapping' this may fix this. Can someone confirm this? 

Also I believe this CPU has the IHS soldered to the processor die, so replacing internal TIM is out of the question, right?

 

I'm using an old Freezer Pro 7 cooler with Arctic MX-4 thermal paste on a ROG Maximus Formula II mobo.

[StevenSensei]

From what I understand, with temp variance that great the chip is a candidate for delidding and TIM replacement. BUT only if it is not soldered...which yours is...so that's no longer an option. Looks like some people have had good luck with lapping the IHC. There was even one guy who actually kept lapping until he got through the IHC and exposed the core...obviously risky and not recommended for the faint of heart. 

 

Given your situation I'd say go ahead and lap the CPU and see if it helps. 

[APasz]

This is above average for that generation (and is extreme compared to today's cpus), wouldn't worry about it too much though.

I haven't actually owned one of these cpu's but from what I have gathered, taking like 0.1-0.3mm off the ihc can improve the issue.

I agree with papakuma3.

[Jonathan Lemmens]

1 minute ago, Papakuma said:

From what I understand, with temp variance that great the chip is a candidate for delidding and TIM replacement. BUT only if it is not soldered...which yours is...so that's no longer an option. Looks like some people have had good luck with lapping the IHC. There was even one guy who actually kept lapping until he got through the IHC and exposed the core...obviously risky and not recommended for the faint of heart. 

 

Given your situation I'd say go ahead and lap the CPU and see if it helps. 

Thanks.

 

So this doesn't mean this is the beginning of the end for me CPU?

As an engineer I'm quite familiar with lapping, though I've never did it with a CPU before. Anything specific i need to watch out for? Do you maybe know of an article or previous thread on this topic?

[StevenSensei]

With lapping just don't put any pressure on the chip. If you have your lapping media on your work surface then put the CPU on top...cover the entire chip with a loose plastic clam shell or toy capsule and lap with just the weight of the chip itself. It's ok if you lap through the coating into the copper but I wouldn't go further than that. You should also use some electrical tape to completely cover the PCB to avoid any possible contamination from any material removed in the lapping process.

[APasz]

3 minutes ago, Jonathan Lemmens said:

Thanks.

 

So this doesn't mean this is the beginning of the end for me CPU?

As an engineer I'm quite familiar with lapping, though I've never did it with a CPU before. Anything specific i need to watch out for? Do you maybe know of an article or previous thread on this topic?

I followed pcauthority article back in 2010 when I did with an almost dead 870 just for shits and giggles.

You can find guides all over the place, like overclock.net. Not sure if there is one on here though.