Adding 4GB RAM to a Macbook 4,1 MB402LL/A

So if you follow the recommended guidelines of purchasing this:

Everything works fine as documented all over the place.  And yes, in equal-sized pairs, the memory bus works at full bandwidth, which takes a 50% hit in throughput if you decide to max the machine out to 6GB (using a 4GB and 2GB SODIMM).

But what if this is 30% less expensive (because as RAM speeds go up, inventories get smaller on the slower end):

Model FA-6400CL5D-4GBSQ
Type 200-Pin DDR2 SO-DIMM
Capacity 4GB (2 x 2GB)
Speed DDR2 800 (PC2 6400)
Cas Latency 5
Timing 5-5-5-15
Voltage 1.8V

Then upon installation, you get the infamous Mac black screen on boot with a sorrowfilled “beep” that let’s you know you were a bad person not to buy the correct RAM.

Except the interesting feature of SO-DIMM modules is that they use firmware on-board to set the run-time attributes for module.

And luckily, there’s wonderful tools like SPDTool and Thaiphoon Burner to adjust those

Application Screenshot

blankety-blank modules. But of course, they also run on Windows-only, so you have to go through the whole Boot Camp Assistant method to slice aside at least 10GB of free disk to make a bootable Windows partition, and actually have a Windows installation CD/DVD/image to work with.

But all of that has been well-documented.  What wasn’t so walk-through was getting SPDTool up and deciding what actually needed to be changed.

Short and sweet, after installing Windows, and placing the one original SO-DIMM alongside one of the new “faster” SO-DIMM’s (which you’re about to slow down to make it compatible with the weirdness that is Mac.) You File -> Read -> ( Module> , which when read, you can match the Model No. displayed to your original SO-DIMM’s to figure out which one is which.  Then you scroll down the settings window (the one full of pull-down list boxes) and find the one named SDRAM Cycle.  My PC2-6400 was set to 2.5ns (400 MHz), and needed to be 3.0ns (333 MHz).

Then File -> Write  -> [same Module as previously Read] – quit the SPDTool and reboot.  If working, shut the computer back down and replace the other original SO-DIMM and repeat the process for the 2nd module.  Presto! You now have 2 PC2-6400 SO-DIMMs that “think” they are actually PC2-5300 modules.

And your Mac is happy again.

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