Just Upgraded RAM why does it say 1333 instead of 1066???

You have some conflicting information that makes an answer difficult. There was only one MacBook with a 2 GHz Core Duo CPU. It requires DDR2 PC2-5300 memory and cannot address more than 2 GB.

To find out, click  > About this Mac > more info and find the hardware identifier. It is probably "MacBook5,1" whose system bus operates at 1066 MHz.

It should run Lion just fine but you need the correct memory for it. Each succeeding OS X version becomes more intolerant of RAM that doesn't meet specifications.

Thanks but none of that is relevant.

besimple1 wrote:

I have a the Mac Book Unibody 2 Ghz Intel Core Duo. ... I know it runs PC3-8500 DDR3 1066 MHz.

...

John Galt wrote:

There was only one MacBook with a 2 GHz Core Duo CPU. ...

To find out, click  > About this Mac > more info and find the hardware identifier. It is probably "MacBook5,1" whose system bus operates at 1066 MHz.

Kindly reconcile this. If yours is a MacBook5,1 then 1333 MHz memory may work but it will not be reliable. If it works with Leopard it may not with Lion.

You could try to be a little less of a jerk when answering questions.

You could try answering mine. I asked twice for your hardware identifier, and twice you chose not to answer. I won't ask again.

Why all this debate of exactly what your machine is? Open System Profiler and post what the model identifer is in the Hardware section.

Also post the Profiler's dimm summary for the Memory.

I am having a similar issue.

I have a Macbook5,1 with a intel core 2 duo 2.4Ghz this is the late 2008 modle that came in both a 2.0Ghz and a 2.4Ghz version.

you can find specs for my model and the model i belive besimple1 has here:

http://www.everymac.com/ultimate-mac-lookup/?search_keywords=MacBook5,1

The computer originally came with 2 GB of 1066 MHz DDR3 SDRAM (in two 1GB sticks). I purchased a upgrade pack of ram (2x4Gb Mushkin PC3-8500 DDR3-1066) and installed it and now the computer tells me I have 8Gb of 1333 MHz DDR3 under "about this mac"

I have found that many people have not had a problem running 8Gb of ram on the macbook5,1 dispite Apple stating the max capacity is 4Gb (plenty of forums online attesting to this)

I purchased the ram from NCIX (a reputable computer store in canada) and so I am sure I got 1066MHz ram.

I am currently running memtest and it is telling me I have only 6100Mb and that there is a "data mismatch" error so I am going to return the ram for a new set, but the original post here leads me to think the miss identification of the ram by the computer may not be due to the problems with the memory memtest is finding.

any ideas as to why the computer says i have 1333MHz ram when I installed 1066MHz?

I will post if a new set of ram fixes this problem

I too have a MB 5.1 Late 08.

Running Lion with 8GB of DDR3 1333Mhz which I specificly ask for.

It registers as 1333Mhz and has not given me any issues.

I'm sure it's only running at 1066 since that's the system bus speed.

From experience in both PC and MAC, you can install a faster spec RAM but not a slower one.

If you bought your RAM at a place that also sells PC RAM you may have gotten mislabelled RAM. PCs can handle different RAM speeds so they’ll often label higher speed RAM as a lower speed rather than make two different speeds of RAM. But Macs are much more picky. They require a RAM stick to be exactly 667mhz not 675mhz or 800mhz. The way to tell is to put one of your old RAM sticks in and it will force the new RAM to run at the correct speed.

This is from one review of PNY RAM:
"These modules are actually 800Mhz. PNY no longer makes or sells 667Mhz modules. Not all computers that require 667Mhz are compatible with 2 800Mhz modules. They refuse to down clock properly. This is especially true with a number of Core 2 Duo MacBooks. Spoke to PNY support, they flat out told me that yes, they sell 800Mhz modules in 667Mhz packaging. If you RMA a module that is 667Mhz (or supposed to be 667Mhz) they will replace it with an 800Mhz module as they no longer have any 667Mhz SODIMMs, not even for RMA replacement!"