For those wondering, a typical SDXC card is the equivalent to the eMMC storage on the slowest Microsoft Surface device available.
That potentially might not even be necessary. They might just need a firmware update. If the SDXC -> SDUC boundry ends up being as artificial as the SDHC -> SDXC one (see SDXC cards on the 3DS, which only officially supports SDHC), they might not even need that.
Well I'm pretty sure you'd just be using exFAT on SDUC, which covers us up to 128 petabytes, but yeah, it already looks clear that SDUC performance targets won't be met and at best we'll just see a smooth increase at scale over SDXC.
Not very scientific comparison:
- Seagate Barracuda (HDD, 2016) 160MB/s read, 130MB/s write
- Samsung EVO 512GB MicroSDXC 100MB/s read, 90MB/s write
- Samsung 850 SSD: 550MB/s read, 550MB/s write
The exciting thing about SDUC is that it dumps UHS-3 for SD Express, a new NVME bus mode, which supports up to 985MB/s. Even if it never reaches a fraction of that, there's solid potential for future SD cards to gain heavily in latency reduction and small reads which could make them feasible standard drives for small devices...if the longevity thing is figured out.
