I recently picked up a Diamond Stealth S540 Xtreme and it's detected with a different GPU, the Savage4 Pro-M 86C396 and not the 86C398. POST shows Xtreme, same with software and driver. Clocks are 160/166 MHz. I'm confused.

This is an identical card, I got mine for a lot less.
https://www.ebay.com/itm/145037702802