Did I hurt my i5-750?

[shadowillusion]

Based on these quotes:

Wrong. This is not the case for current Intel Platform. For LGA1156(P55/H55/H57), the DRAM voltage (VDIMM) and CPU VTT voltage (QPI/VTT) have to be within a 0.5V delta (If VTT is 1.2V, VDIMM cannot be more than 1.2V+0.5V=1.7V), otherwise you may end up with hardware malfunction and/or damaged IMC of the CPU.

http://www.intel.com/design/corei7/documentation.htm

Intel® Core™ i7-800 and i5-700 Processor Series Datasheet - Volume 1

p.67 and p.69 mentioned the absolute and normal operation specifications of VTT/DDQ(VDIMM).

So here is the whole story:

My Mobo: Gigabyte H55-USB3

My CPU: Intel i5-750

My DDR3: Corsair Dominator TR3x6G-1600C8D >> I mistakenly buy these triple channel kits... I know it would be only dual channel in H55... This are where the problem starts...

- i5-750 default memory controller speed is 1333mhz...

- when I enable XtremeMemoryProfile (XMP) (1600 mhz 8-8-8-24, dram 1.65v, qpi 1.35v), my CPU VCore is 1.28V, temp is 56C (idle) to 99C (throttled because reached TJMax) (100% load)... It also OC'ed my CPU to 3.2Ghz...

- when I disable XMP (1333 mhz 9-9-9-24, dram 1.5v, qpi 1.1v), my CPU VCore is 1.184v, temp is 40C (idle) to 78C (100% load)... My CPU stays at 2.66Ghz...

Because of that 99C throttled, I pulled up some facts:
- I already reseated my CPU
- 6 fan cooled case. No problem with the case
- Fan maxed out at 2500RPM++. No problem with the fan
- Stock fan, stock paste, stock frequency no OC

So I asks the shop to replace my CPU with the new one... Still the same temp even with this new CPU...

Then I thought maybe 1.28v VCore is too high... So I am thinking to undervolts VCore to makes my CPU temp never goes above 72.7C (TCase spec for i5-750 based on intel websites)

Now there are three reasons why I thought I might hurt my i5-750:
1. It reaches TJMax and therefore the CPU is throttled... Happens about 10 minutes...

2. I realized XMP (which is supposed to X58 that can handle more qpi voltage) gives a wrong qpi voltage to H55. It puts 1.35v while intel says H55 max is 1.21v... It can hurt my i5 IMC... I already put XMP on for 1 ~ 2 hours...

3. The next stupid thing is, I modified the BIOS to makes DRAM voltages at 1.66v and qpi voltages at 1.1v (stock default)... 1.66v - 1.1v means 0.56v delta... More than 0.5v allowed... Look at the quoted posts above... I put this mode on for 1 hours...

After these three things happened, I realized my mistake (because I read some forums by googling)... Then while I'm regretting this, I continued some testing...

And here is my final config:
- 1.1v >> 1.21v qpi voltage
- 133 >> 160Mhz blck (OC 'ing the CPU from 2.66 > 3.3Ghz and my DDR3 from 1333 to 1600Mhz)
- 1.5v >> 1.64v DRAM voltage
- Makes all memory timings and settings from default to the same as XMP
- 1.28v >> 1.0375v VCore CPU voltage (undervolted)

Because of the undervolted VCore, the temp went down from 99C to 72C... Prime95 CPUStress test gives no error... Mission accomplished!


The Question:
1. As the title of this post says... Based on the three occurences above, did you think that my CPU is already damaged? For now it's still doing fine, though... Do I need to replace it again? But this time it's clearly my mistakes because of experimenting without read further

2. Is it normal if I enable XMP the temp at stock VCore reaches 99C?

 

[MattNo5ss]

Since you get the same temps with two different CPUs that makes me think there is a bad heatsink mount. What heatsink are you using?

If you have everything at stock, you should not overheat even with the stock Intel cooler (unless there is a bad mount, way too much TIM, or both).

 

[Bobnova]

At stock it didn't overheat, when XMP was turned on the bios overvolted quite a bit and jacked the temps up. The stock fan couldn't take it.



Your CPU is fine if it's running stable, it's lifespan may be marginally shorter, or it may not. It's maximum OC may now be lower, or it may not.
Unless it's failing to run at stock clocks, it's officially just fine.
As long as it is doing what you want it to do, you (and it) are fine IMO.

 

[shadowillusion]

@Matt,
I already tried to reseat my CPU several times with the old CPU... and then after they gives me this new CPU that suffered three occurences above, it still reach 99C when XMP is enabled...

That is, I don't think it's normal for a cpu with stock cooler to be 99C when XMP is enabled and therefore it's OC'ed to 3.2Ghz... Even with XMP disabled (everything default, 2.66Ghz) I still get 84C at max load...

If only someone that has i5-750+stock cooler+xmp enabled could share the same thing

@Bobnova,
now it's run okay at 3.3Ghz, undervolted from 1.28v to 1.04v... I'm thinking to asks a replace again from the shop, but this time I don't have any clear reason besides my stupid three mistakes above

 

[Bobnova]

I wouldn't worry about it, personally. If it runs 3.3ghz on 1.04vcore it's fine.

It sounds like your motherboard's implementation of XMP is pretty terrible.