I am just putting this warning online for other people. It's about RAM compatibility for the MacBook Pro 2010 models. Here are the RAM facts on the 2010 MacBook Pro series, for those curious: - The 13" models have a nVidia 320m which doesn't have any dedicated video RAM. Instead, it shares the system RAM. And that video chip can only speak at 1066 MHz (max). If you try putting in faster RAM (such as 1333 MHz), the SYSTEM itself supports 1333 MHz and runs the RAM at that rate, but the nVidia VIDEO chip doesn't support that RAM speed. So your system begins starting up, and the CPU negotiates 1333 MHz speed since "it supports it", but as soon as the VIDEO driver is loaded the graphics card crashes the computer because the video chip cannot talk to the system RAM at that speed. If you boot into safe mode (no video driver is loaded), the system will "work" since no video driver is loaded, but it will of course be super slow. - The 15" models and up have a nVidia GT 330m which DOES have its own completely dedicated video RAM and isn't dependent on system RAM. These models purportedly support 1333 MHz RAM out of the box since there's no problem with the video card on these higher-end MBPs. And it makes sense that it would work, since MBP 2008/2009 supports 1333 MHz RAM at native speeds. Although I cannot make any guarantees. My personal model is a MacBookPro6,2 (Mid-2010 MacBook Pro, 15", with GT 330m graphics). Anyway, my MBP 2010 15" had a RAM failure in one of my 2x Kingston 4 GB 1066 MHz MBP2010-certified RAM (KTA-MB1066K2/8G). It was a kit of 2x4 GB sticks, and each stick uses DUAL-RANK memory. Unfortunately, Kingston no longer sells any MBP2010 certified RAM so they couldn't give me the same stick as a warranty replacement, but they allowed me to replace the faulty stick with one that had a slight chance of working. They gave me a KCP313SS8/4. It's a 1333 MHz, SINGLE-RANK 4GB stick. And they said that it might not work; because "the memory controller in your CPU probably supports single-rank, but probably DOESN'T support the size of the individual memory chips we use in this single-rank RAM". So what's the "rank"? Well, it's specified on any RAM you buy. There's either single-rank (1R) or dual-rank (2R). Single means that ALL memory modules are handled by a SINGLE controller chip. Dual rank means they're divided among TWO controller chips. When you have a single memory controller chip, the individual RAM chips (the ones on the RAM board) must be larger, since there's only room for a certain number of chips per controller. So a 4 GB dual-rank module may consist of 16x 256 MB chips (8 chips per RAM controller chip on the board). But the same as a single-rank module would have to be something like 8x 512 MB chips (8 memory chips on the single RAM controller chip on the board). And that's where the problem happens: THE MACBOOK PRO 2010 CPUs DO *NOT* SUPPORT LARGE INDIVIDUAL MEMORY CHIPS. AND IF YOU BUY SINGLE-RANK RAM YOU'RE ALMOST GUARANTEED THAT THE MEMORY CHIPS ARE GOING TO BE LARGE ONES. In other words, this new stick does not work. When booting up, I always get a "page fault" kernel panic, which means the CPU is unable to speak to the RAM properly. If anyone is going to upgrade their MBP 2010 RAM, these rules apply: - The MBP 2010 13" models support 16 GB of RAM (due to some fluke of the design, I forget what), at 1066 MHz. - The MBP 2010 15" and up models support 8 GB of RAM. - The MBP 2010 15" and up models with the GT 330m should support 1333 MHz RAM out of the box, but don't take my word for it. Only 1066 MHz is 100% guaranteed to work. - Whatever you do, DO NOT buy single-rank RAM for either of these models. You need dual-rank RAM. - Kingston no longer manufactures ANY compatible RAM for the MBP 2010 series. But Crucial etc still have some RAM models that work, for those who need RAM. That's it. I just wanted to dump this info online so others may get helped by it in the future, and avoid wasting time with single-rank RAM like I just did.