New ram, one stick possibly defect

[Nizhny Tagil]

My system:
Mobo: Asus P5QC
CPU: Q9550
RAM: 2x2GB Corsair XMS2 DDR2 1066
PSU: Bequiet SP7 450
HDD: 1 SSD, 2 7200 RPM, 1 5400RPM
VGA: Geforce GTX750Ti KalmX

I've bought and tested the exact G.Skill model suggested to me here: http://www.tomshardware.co.uk/answers/id-3159536/p5qc-8gb-memory.html .

At first I've tried booting with both sticks installed and it wouldn't boot.
Then I've tried booting with a single stick, first in one slot then the other. I've tried this with each stick: with one, the computer would boot, with the other it wouldn't, no matter into which slot I put it.
I've only used the correct orange slots for DDR3.

I figured that, rather than this model being incompatible, one of the two sticks is defective; so I'm returning the kit and having it replaced with a new one of the same.

Now, I'd like to know if my guess is correct or there's something I'm missing, since it's the second time I try to install 8 GB of DDR3 without success.
Thanks.

 

[RaDiKaL_]

So you've already got the replacement sticks and still doesn't work? you could test each stick individually with memtest86+ to see if you've got again one DOA.

 

[Nizhny Tagil]

No, I meant that now I have to return the kit and have it replaced with a new one, hopefully not defective.
Basically, I want to make sure I've done all I could to make it work before sending it back.
I'm sorry, my English isn't very good.

Anyway, as I've said, I've tested each of the two sticks individually first in one slot, then in the other (to see if maybe the slots weren't working). With the stick that I suppose isn't working, the computer wouldn't even boot to BIOS, so I think even running memtest86+ wouldn't be possibile.
With the other, the computer would boot fine, no matter which slot I'd put it into.

 

[geofelt]

You may have a different problem.
Yes, I think your analysis is correct if one stick works and the other does not.
That one stick is likely defective.
The problem comes with trying to add two sticks which are presumably the same.
They will not be exactly.
A motherboard must manage all the ram using the same specs of voltage, cas and speed.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards can be very sensitive to this.
That is why ram vendors will NOT support ram that is not bought in one kit.
You want documented ram compatibility. If you should ever have a problem, you want supported ram.
Otherwise, you risk a finger pointing battle between the ram and motherboard support sites, claiming "not my problem".
One place to check is your motherboards web site.
Look for the ram QVL list. It lists all of the ram kits that have been tested with that particular motherboard.
Sometimes the QVL list is not updated after the motherboard is released.
For more current info, go to a ram vendor's web site and access their ram selection configurator.
Enter your motherboard, and you will get a list of compatible ram kits.
While today's motherboards are more tolerant of different ram, it makes sense to buy a single ram kit that is known to work and is supported.

 

[Nizhny Tagil]

You may have a different problem.
Yes, I think your analysis is correct if one stick works and the other does not.
That one stick is likely defective.
The problem comes with trying to add two sticks which are presumably the same.
They will not be exactly.
A motherboard must manage all the ram using the same specs of voltage, cas and speed.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards can be very sensitive to this.
That is why ram vendors will NOT support ram that is not bought in one kit.
You want documented ram compatibility. If you should ever have a problem, you want supported ram.
Otherwise, you risk a finger pointing battle between the ram and motherboard support sites, claiming "not my problem".
One place to check is your motherboards web site.
Look for the ram QVL list. It lists all of the ram kits that have been tested with that particular motherboard.
Sometimes the QVL list is not updated after the motherboard is released.
For more current info, go to a ram vendor's web site and access their ram selection configurator.
Enter your motherboard, and you will get a list of compatible ram kits.
While today's motherboards are more tolerant of different ram, it makes sense to buy a single ram kit that is known to work and is supported.

Are you suggesting I buy a whole different kit?

Anyway, both sticks were sold as one kit on Amazon and I've bought them there as one kit: https://www.amazon.it/gp/product/B004G8KCGO/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1.
They're absolutely the same and their serial numbers are consecutive (one is ***165, the other ***166). That's why I thought one of them must be broken.

I'd like to add I've been pointed to that exact kit by a moderator of this forum that assured me it was compatible.
It wasn't listed in the mobo's QVL and the mobo wasn't listed in the RAM's QVL, but I've linked in the first post the thread were he said it should have been fine.
Plus, the RAM's model is advertised as compatible with my mobo's chipset (P45) on many sites (though not on G.Skill's site).

All that said, I've ruled out the possibility of an incompatibility issue.
I think it's unlikely that of two sticks bought in a single kit one is compatible and the other isn't.

I just want to be extremely sure before I send it back and replace it with an identical one, hopefully working this time.

 

[geofelt]

Sometimes parts come defective.
You have done due diligence.
Memtest is the gold standard for testing ram.
The fact that one stick works, would indicate that the ram is compatible.
The ram vendor can not be expected to test their ram with every motherboard on the market.

 

[Nizhny Tagil]

Sometimes parts come defective.
You have done due diligence.
Memtest is the gold standard for testing ram.
The fact that one stick works, would indicate that the ram is compatible.
The ram vendor can not be expected to test their ram with every motherboard on the market.

I don't know how to test the defective stick with Memtest, because (as I've said above), with said stick (even if only that) installed the computer wouldn't even boot to BIOS. I mean, I should at least be able to access the BIOS to choose the option to boot from CD to do the test, right?

 

[geofelt]

No, if it won't boot, you can't test. Consider the kit to be defective