You can force full memory retraining by resetting your PRAM ( Option Command P R during boot). Buy A-Tech 8GB RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010 27 inch 4-Core, Mid 2011 21. Although I can’t think of a good reason why it would only happen for the 4+4 case, your firmware may not be recognizing a new DIMM has been installed and is trying to use a stale memory training table with the new card.When you ran your experiment, did you try both of the DIMMs alongside the 2 GB DIMM? And then did you try each of those DIMMs in the other slot alongside the 2 GB? In other words, you should have performed this experiment with FOUR different memory configurations.

It may be that one of your 4 GB SO-DIMMs is of marginal quality and is failing during one of the training steps.Now let’s consider a couple of possibilities: According to Apple, the mid-2009 MacBook Pro does support up to 8 GB:ĤGB (two 2GB SO-DIMMs) of 1066MHz DDR3 memory two SO-DIMM slots support up to 8GB Let’s consider the most common.įirst, let’s make sure your system supports 8 GB. 3 beeps + 5s pause means your memory failed training.

Apple macbook pro 2011 memory upgrade