If you have an iPhone 3G and are regretting upgrading to the über sluggish iOS4 there is still hope!

Honestly, Apple should have excluded the 3G from iOS4 altogether. The iPhone 3G is essentially the exact same hardware as the initial EDGE iPhone with the addition of a 3G chip. Which means it’s still a 412mhz processor & 128mb of …RAM. By contrast the iPhone 3GS uses a 600mhz clocked processor & 256mb. The new iPhone4 runs the same A4 processor the iPad uses (capable of 1ghz that is under-clocked to somewhere in the 800mhz range) with 512mb of RAM.

For the less technically inclined this means the old EDGE iPhone & the 3G will have the same basic performance, but the 3GS & 4 are each progressively faster. iOS4 is simply too resource intensive for the older hardware to run effectively. iOS4 will run on the 3G ok, but you will have varying degrees of lag.

It has been reported (via MacRumors) that Steve Jobs has claimed (via emial reply that) the performance of iOS4 on the 3G will be addressed in a future software update. This most likely being 4.1 when it is released, but of course there are no guarantees as to what level of performance increase we should expect. In the meantime those of us with iPhone 3G’s are left with devices that are so sluggish and buggy they are barely considered usable. (Personally, I do NOT consider it usable.)

One potential option to try before the more technical process of downgrading you can try turning off Spotlight. SETTINGS >> GENERAL >> SPOTLIGHT and then uncheck all the items. This seems to speed up some 3G running iOS4 slightly, but during my testing I found little to no perceptible difference.

I ran a couple of the beta versions of iOS4 and downgraded back to 3.1.3.  Later when Apple released the update to the public I tried the various 4.0 & 4.0.1 releases and each were almost as bad as the beta. If you want a “snappy” device and you’re using a 3G then downgrading is likely exactly what you need.

There is terrific writeup on how to accomplish this over at iPhoneHacks that will walk you step by step through this process. It is worth noting that if you only have backups stored from when your device was running 4.0 or higher you will not be able to restore from a backup. This is annoying, but could likely be the lesser of two evils when dealing with a phone that is barely responsive.

January 2011 UPDATE: It seems that Apple has fixed most of the usability bugs found in the early version of iOS4 with the current iteration of 4.2.1. This is a very good things, as it currently it appears as if Apple intends to cease support for the iPhone 3G with 4.2.1. If you want new features you’re going to have to upgrade soon.