The AT&T Samsung Galaxy S4 is getting its first firmware upgrade.

The upgrade follows the release of an update for the Galaxy S4 on T-Mobile on the morning of Tuesday, May 7. T-Mobile users of the S4 became the first in the U.S. to receive the upgrade. The update for the AT&T device is slightly over 20 MB in size and it hasn't been revealed yet exactly what it offers. However, some have reported smoother animations and faster performance. Lag fixes would likely be welcome for many, given some reports of jitteriness in the Sprint U.S. Galaxy S4.

In contrast, it is known what was made available with the update on T-Mobile. That upgrade included improvements to visual voicemail and the ISIS app.

To access the software update on your AT&T Samsung Galaxy S4, go to Settings -> More -> About Device -> Software Update. If nothing appears, try connecting your device to a computer and use Samsung's Kies desktop software. Downloading and installing the update should only take a couple of minutes. The update should be included once your Galaxy S4 is rebooted.

Stay tuned for additional updates for the AT&T Galaxy S4, as many more updates should roll out. Samsung likes to update its devices and although it's unclear when the next smaller software update will arrive, expect a big one with the release of Android 4.3/Android 5.0.

We may be seeing Android 4.3 Jelly Bean or Android 5.0 Key Lime Pie at the upcoming Google I/O event, as Google is rumored to be presenting something big in the software arena.