Types of RAM

When you upgrade your laptop’s RAM, you need to know which kind of RAM your laptop came with originally and which kinds of RAM are backwards compatible with that original memory. Here are the different types of RAM Apple has shipped in laptops over the last several years and the kinds of newer RAM that are backwards compatible with them.

Types of RAM

Speed Type Maximum bandwidth Backwards compatible with… Notes
PC100 SDR 0.8 GB/sec PC66 100 MHz bus, popular up to 2001. You’ll also see PC100 dual-layer, which is constructed in two layers; older machines (including the early PowerBook G3) can’t use it.
PC133 SDR 1.1 GB/sec PC100 Last shipped with the PowerBook G4 ‘DVI’.
PC2100 DDR 2.1 GB/sec DDR (double data rate) RAM sends data twice per clock cycle. Also known in the PC world as DDR266.
PC2700 DDR 2.7 GB/sec PC2100 Used in the newest iBooks and Mac Mini.
PC3200 DDR 3.2 GB/sec PC2100, PC2700
PC2-4200 DDR2 4.2 GB/sec Not backwards compatible with DDR.
PC2-5300 DDR2 5.3 GB/sec PC2-4200

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