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I've got an Early-2009 Unibody Mac Book Pro 17".

It came with 4 GB RAM and by default it boots into 32-bit Kernel.

I've just upgraded to 8 GB RAM and my main concern is getting maximum performance from my 64-bit version of Lightroom 3 (I scan negatives and edit large tiff files).

Now that I've got 8 GB RAM, will booting into 64-bit Kernel give me any performance boost on Lightroom (and even generally)?

Should I see a performance boost on 32-bit Kernel with the additional RAM?

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Adding RAM should give you performance improvements unless you had a lot to begin with. It might be a little faster to use the 64 bit kernel, but it probably won't make much difference compared to doubling the RAM. – ughoavgfhw Mar 10 '11 at 22:49
up vote 5 down vote accepted

According to this article at, you will see performance gains (5-30%) by running graphics applications in 64-bit mode.

Note that you don't necessarily need to switch to a 64-bit Kernel, you just need to ensure that Lightroom runs in 64-bit mode.

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According to this other article at, you'll get an additional (generally small) performance boost from running under a 64-bit kernel as well. In that article, he saw a 3% speed increase importing files into Lightroom 2.4 (that's in addition to the 27% speed increase from running Lightroom itself in 64-bit mode). – Gordon Davisson Mar 16 '11 at 14:37

As per Apple's web site, no.

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