What is this tiny board?

[Silksbian]

I've opened up this NTSC-U Dreamcast to try and fix the laser and noticed this board. I've never seen this board before on any Dreamcast teardown I've watched, any idea what it is? It was covered in more red electrical tape so I assume someone else has been inside it before, any idea what it is?

[tomcioPL]

Additional RAM maybe? Idk though

[pcwzrd13]

It's a 4-wire region-free modchip.