The real significance of the iPhone is that it’s a powerful Unix box that sits in your hand. But exactly how powerful is it? John Gruber approached the problem by asking: “which Mac does it most closely resemble in terms of specification?. Here’s his answer, which is based on some clever digging by Craig Hockenberry:

So, my answer to the question: the original “Pismo” G3 PowerBook. The numbers match up pretty closely: 400 MHz CPU, 100 MHz bus speed, 64 MB of RAM. (The higher-end Pismo had a 500 MHz CPU and 128 MB of RAM.) Even storage sizes are similar: hard drive options for the Pismo were 6, 12, or 18 GB. Another possible answer: the original blue-and-white Power Mac G3 — again, 400 MHz CPU, 100 MHz bus speed, 64-128 MB of RAM, and 6-12 GB hard drives. Think about that — in just nine years, the specs that then described Apple’s top-of-the-line desktop computer now describe their phone.

So — it took about eight years to get a G3 PowerBook into a phone. That means that in eight years’ time we’ll get a MacBook Pro into a phone.