On the last iPhone Live!, Dieter, Phil and I discussed iPhone 4.0 and whether, as rumors suggest, we'd finally see multitasking brought to the platform. That's when the discussion turned to RAM. The iPhone 2G and iPhone 3G have an anemic 128MB of RAM. The iPhone 3GS has 256MB. That's the same amount as the original Palm Pre and Motorola Droid, which do multitask but do bog down and sometimes error out while doing it. Just-released phones like the Palm Pre Plus and Google Android Nexus One up the ante to a beefy 512MB of RAM.

What does this have to do with the iPhone and multitasking? We've seen time and time again that Apple would rather not offer a feature at all then offer one with a poor user experience. It's why we waited for copy and paste until iPhone 3.0, and why the iPhone 3GS does 30fps video recording and even though the iPhone 3G could do half that, maybe, Apple won't enable it.

When Push Notification was announced, head of iPhone software Scott Forstall made fun of Windows Mobile-style task management on a mobile device, and sighted battery drain as the primary reason Apple wasn't doing it. Let's assume Apple gets better battery life in the 4th generation iPhone as well, unless they get more RAM, it's still tough to see them enabling multitasking unless and until they beef up the RAM so that at least a few apps can run in the background with as much smoothness and reliability as Apple demands.

Will iPhone 2G get another free update to iPhone 4.0 when it's released? Will it get the full update, unlike 3.0 when it didn't get MMS or A2DP. Will iPhone 3G, when it didn't get video recording? Will iPhone 3GS?

If RAM is the thing that will dictate iPhone multitasking, 512MB (or more?) might just be the magic number, and potentially the magic cut off (or scale back) as well.