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 |