Revision 1.6 / 1.6b
Revision 1.6 / 1.6b (No TSOP)
The 1.6 and its later variant 1.6b are the final Original Xbox motherboards. They introduced cost-saving changes including a different video encoder and, most importantly for modders, a different flash memory chip.
The defining limitation of these boards is that they cannot be TSOP flashed. The flash chip used on 1.6/1.6b is not writable by the standard process, so the modchip-free custom-BIOS route available on earlier boards does not apply here.
What still works
Do not let the TSOP restriction discourage you. The ENDGAME softmod recommended works perfectly on 1.6 and 1.6b, giving you homebrew, emulation, media playback, and a custom dashboard with no soldering and full reversibility.
If you want a hardware solution, a modchip such as the OpenXenium or Aladdin XT/XT Plus2 is fully supported. These supply their own BIOS and sidestep the unflashable onboard chip entirely.
Other notes
The 1.6 boards changed the video encoder, which can affect certain advanced display tweaks, but this has no bearing on standard softmodding. The clock capacitor concern is generally less pronounced on these newer boards, though inspecting it remains good practice.
Best path for 1.6/1.6b
Softmod for simplicity, or a modchip for a hardware-backed setup. Either way, back up the EEPROM and its HDD key first.