I bought some G-Skill 8 GB RAM (2x 4GB) for my MacBook Pro. It's supposed to be cable of holding 8 GB of RAM but it seems it only wants to recognize 6 GB. I tried putting the 2 matching sticks in together and it boots, and you hear the noise, but it starts loading and you see the spinning wheel but it won't quite get to the login screen.

I took out one of the 4 GB sticks and popped in one of the original 2 GB sticks that came with the machine in its place. It booted up perfectly, and I was able to use it just fine.

I tried to shake things up and see if it was possibly a defective stick. I switched one of the new 4 GB sticks for the other to see if it worked. It did, and it booted up properly and that's what I'm using to type this message right now.

My question is, what else needs to be done to get this working? The only thing I can think of that I could be doing wrong is the RAM is DDR3-1333, and the machine is limited to 1067 by the motherboard. Any advice would be greatly appreciated.

Sounds like you should send it back and get the proper RAM

Sounds like you should send it back and get the proper RAM

+1, match the ram to the machine.

Try installing one stick at a time that will help identify faulty ram!

You need to get the proper matching RAM and you've got a mismatch and not all DDR3-1333 RAM is backward compatible, especially with a mismatch of types.

"DDR3 SDRAM is neither forward nor backward compatible"

"DDR3 SDRAM is neither forward nor backward compatible with any earlier type of random access memory (RAM) due to different signaling voltages, timings, and other factors."

DDR3 SDRAM - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/DDR3_SDRAM)

Memory upgrades from Crucial.com - Memory speeds and compatibility (http://www.crucial.com/support/memory_speeds.aspx)

Well Thats not necessarily true. I'm currently running 4gb of 1333 ddr3 in one of my 09 13" MacBook pros and it works just fine. I think a lot of it is going to depend on the RAM used and obviously the stuff he has bought isn't compatible to run at speeds other than what it's designed to...

Try installing one stick at a time that will help identify faulty ram!

Did you read the post? He has done that. Both sticks work solo, it's only when they are installed together the issue presents itself

Well Thats not necessarily true. I'm currently running 4gb of 1333 ddr3 in one of my 09 13" MacBook pros and it works just fine. I think a lot of it is going to depend on the RAM used and obviously the stuff he has bought isn't compatible to run at speeds other than what it's designed to...

My understanding is if the Mac needs 1066 RAM speed, the RAM type cannot be mixed with different types. ie: if all chips are DDDR3, then DDR3-1066 and DDR3-1333 chips can be installed and will all work at the 1066 speed.

Its when the DDR3 chips are inter-mixed with DDR2 chips and I believe the fastest are 1066, that's when things go goofy.

IE: either all DDR2 or all DDR3 chips, but just not a combination of the two DDR types.

EDIT: Re-reading the OP message and a check at everymac shows the MBP would have come with DDR3 Ram so that "mixing types" wouldn't apply and the two 4GB chips should work.
How do you upgrade the RAM in the "Mid-2009," "Mid-2010", "Early 2011," and "Late 2011" 13-Inch, 15-Inch, and 17-Inch MacBook Pro models? How much RAM of what type do they actually support? @ EveryMac.com (http://www.everymac.com/systems/apple/macbook_pro/macbook-pro-unibody-faq/macbook-pro-13-15-17-mid-2009-how-to-upgrade-ram-memory.html)

One thing to try with both new 4GB chips installed is to give the MBP a longer time to boot, which can happen it seems on the first boot with a large increase in installed RAM.

And oh yes, is the Software Update all up to date and any possibly needed firmware type stuff installed??

I took out one of the 4 GB sticks and popped in one of the original 2 GB sticks that came with the machine in its place. It booted up perfectly, and I was able to use it just fine.

I tried to shake things up and see if it was possibly a defective stick. I switched one of the new 4 GB sticks for the other to see if it worked. It did, and it booted up properly and that's what I'm using to type this message right now.

Try installing one stick at a time that will help identify faulty ram!

Did you read the post? He has done that. Both sticks work solo, it's only when they are installed together the issue presents itself

Actually the original post states that he used the 4g and the 2g together, not one stick at a time. I am not sure if that might be what johnnydee means, Try just the 4G stick and then swap it for the other 4G to see if one is bad, not using the original 2G stick.
I still think it's a compatibility issue though.

It seems some other MBP users have had troubles with their G. Skill 8GB Ram kits:
G.SKILL 8GB (2 x 4GB) 204-Pin DDR3 SO-DIMM DDR3 1333 (PC3 10666) Laptop Memory Model [Archive] - MacRumors Forums (http://forums.macrumors.com/archive/index.php/index.../t-1105991.html)

And also at another discussion board where the following is interesting:
"Just cancelled my order from Newegg for G.Skill F3-10600CL9D-8GBSQ memory kit when I came across a review from someone having the same problems as alanngnet. This is the response from G.Skill to his comments:

"Dear Customer

We are sorry to hear the memory is not working properly. This memory kit is not for Apple computers. For 2011+ MacBook Pros, we recommend the G.Skill FA-10666CL9D-8GBSQ. This is the correct model, and it is perfectly compatible. Please contact NewEgg to make the exchange and a replacement should work flawlessly. For any further questions or issues, feel free to contact us directly.

Thank you
GSKILL SUPPORT"
https://discussions.apple.com/thread/2771525?start=0&tstart=0

Maybe the OP got the wrong kit???

And I'd agree withe your compatibility issue comment as the quoted support quote seems to imply.

Maybe the OP got the wrong kit???

Of course he did. From the original post:

The only thing I can think of that I could be doing wrong is the RAM is DDR3-1333, and the machine is limited to 1067 by the motherboard.

The OP needs to get the correct RAM, not faster 1333 MHz RAM on a 1067 MHz logic board.

Obviously it seems. And also confirmed by Mac users at the newegg review page for Mac compatibility.

They need the proper Apple labeled kit for a few $$ more. Maybe the extra charge is to cover any testing and attaching the Mac compatible sticker. ;)

They need the FA-10666CL9D-8GBSQ Apple 8GB RAM kit NOT the F3-10600CL9D-8GBSQ kit.
Newegg.ca - G.SKILL 8GB (2 x 4GB) DDR3 1333 (PC3 10666) Memory for Apple Model FA-10666CL9D-8GBSQ (http://www.newegg.ca/Product/Product.aspx?Item=N82E16820231299&Tpk=FA-10666CL9D-8GBSQ)

You need to get the proper matching RAM and you've got a mismatch and not all DDR3-1333 RAM is backward compatible, especially with a mismatch of types.
"DDR3 SDRAM is neither forward nor backward compatible"
"DDR3 SDRAM is neither forward nor backward compatible with any earlier type of random access memory (RAM) due to different signaling voltages, timings, and other factors."

Nope, has nothing to do with the question at hand. This is talking about the difference between DDR2 and DDR3 RAM which are different physically and electrically. You can't install a DDR2 in a DDR3 slot without a hammer.

Its when the DDR3 chips are inter-mixed with DDR2 chips and I believe the fastest are 1066, that's when things go goofy.

IE: either all DDR2 or all DDR3 chips, but just not a combination of the two DDR types.
No again. The difference between DDR3-1333 and DDR3-1066 is NOT a differenc between DDR2 and DDR3. It is between 2 speeds of DDR3

They need the FA-10666CL9D-8GBSQ Apple 8GB RAM kit NOT the F3-10600CL9D-8GBSQ kit.
Newegg.ca - G.SKILL 8GB (2 x 4GB) DDR3 1333 (PC3 10666) Memory for Apple Model FA-10666CL9D-8GBSQ
No again. The OP needs DDR3-1066 Apple compatible RAM, NOT DDR3-1333
The 1333 may clock down properly or it may not. But replacing the wrong generic RAM with the wrong Apple compatible RAM is not the solution.

Thanks for the corrections CanadaRAM and I should have known better and just said wrong Ram and left it at that. ;)

But maybe you could clarify my confusion about speed and "backward compatible" when some sites such as Crucial say:
"Memory is designed to be backward-compatible, so generally speaking, you can safely add faster memory to a computer that was designed to run slower memory. However, your system will operate at the speed of the slowest memory module. "
Memory upgrades from Crucial.com - Memory speeds and compatibility (http://www.crucial.com/support/memory_speeds.aspx)

Not in real working computer life it seems and a bit too general statement.