iOS 4 performance on older devices (updated)

Apple's iOS 4 is out and while it will work on devices as far back as the iPhone 3G, some users are reporting sub-par performance on older devices.

Apple's iOS 4 (formerly iPhone OS 4) is out and has a ton of new features including multi-tasking, folders, a richer email client (with a true universal inbox) and iBooks. While it runs great on the iPhone 3GS (and presumably, the iPhone 4) performances issues arise when running the new OS on older devices.

Some readers have emailed me their concerns with running the new OS on the soon to be two-generation old iPhone 3G - released in 2008. One reader expresses his concern that iOS 4 running on the iPhone 3G is a "poor combination:"

It is especially bad when network access is active, where keyboard presentation, tapped key response, or screen updates come to a halt.

The map refreshes are very slow, even the unlock is messed up. Often an unlock will jump to the current screen before the sllider moves across the screen. This is not a faster than expected result, it can 5 seconds or more for the unlock to occur staring at the slider. One will question if the gesture was recognized by the phone.

I've been testing the OS since beta 3, some improvement in speed, definite improvement in reliability, but sluggish is the best description of the performance.

previously blogged that part of the problem could be due to insufficient RAM. The iPhone 4 ships with a whopping 512MB RAM, while the iPhone 3GS with 256MB. The lowly iPhone 3G, on the other hand, comes with only 128MB -- one fourth of what ships with the latest model.

In its compatibility statement, Apple says that iOS 4 works with iPhone 4, iPhone 3GS, and iPhone 3G. Adding that "not all features are compatible with all devices. For example, multitasking is available only with iPhone 4 and iPhone 3GS."

Translation: it will work on the iPhone 3G but don't have high expectations.

Update: Another comment:

Another note, the iPod Touch 2nd gen device running the same OS is fairing better, I suspect that the lack of phone features trims the OS demand for realtime background processing, allowing that platform to run as fast as before. But I see little benefit to the OS upgrade on that platform for now, until perhaps Skype gets released and iBooks appears on it (also missing from the GM).

Have you installed it yet? What has your experience been?

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