The Galaxy S5 was sort of an awkward flagship. It wasn't all that different from the S4, which itself wasn't all that different from the S3. Samsung had a bit of an iterative run there before it shook up everything with this year's S6.

Since the S5 isn't two years old yet, the device still has quite a bit of life left. But right now owners on AT&T's network aren't getting Marshmallow. They're getting Android 5.1.1 as part of build number G900AUCU4COI5.

This may not be the most exciting update anymore, but it's a pretty decent jump from 5.0. You know, bugfixes and such. This OTA also brings Android for Work, and an Ultra Power Saver mode fix for encrypted devices.

Upgrade Device Software for the Samsung Galaxy S5 (G900A)

Instructions:

Update summary        

AT&T released a software update for the Samsung Galaxy S 5 (SM-G900A) on October 22, 2015. The update is available via download using Firmware Over The Air (FOTA). Wi-Fi is required for the update.
Software update includes

  • Android 5.1.1
  • Android For Work
  • Security updates
  • Fix to Ultra Power Saver mode for devices using On Device Encryption

Verifying the update

  1. Drag down the notification bar, and tap the Settings icon.
  2. Scroll to the "System" category, and tap About device.
  3. The following information displays:
    • Android version: 5.1.1
    • Baseband version: G900AUCU4COI5
    • Kernel version: 3.4.0-586384
    • Build number: LMY47X.G900AUCU4COI5
    • Upgrade file size: 609MB-999MB