Cross-post comment:

Geerling also demonstrated that the 2GB Pi 5 comes with a couple of unexpected benefits that Upton didn't mention in his announcement—that the 2GB Pi 5 runs a little cooler and uses a little less power than the 4GB and 8GB editions. The 2GB Pi used just 2.4 W or power at idle and 8.9 W during a CPU stress test, compared to 3.3 W and 9.8 W in the 4GB version. The SoC of the 2GB Pi measured 30° Celsius at idle and 59° under load, compared to 32° and 63° for the 2GB version. Those are all small but significant differences, given that nothing has changed other than the SoC.

As to the exact functionality that was removed from the chip for the 2GB version of the Pi, the company hasn't gotten specific. But Geerling speculates that it's mostly related to functionality that's being handled by the custom RP1 I/O chip—RP1 handles the Ethernet and USB controllers, display interfaces, and GPIO, among other things.

So is it worth stepping down to a 2 GB Pi 5 just to get the simpler D0 chip? No. But is it cool to have a cheaper 2 gig option exist? Yes. Just make sure you have a use case for it that doesn't need a ton of RAM.^[[1] https://www.jeffgeerling.com/blog/2024/new-2gb-pi-5-has-33-smaller-die-30-idle-power-savings]