The Arduino UNO R4 boasts a 3x performance increase over the UNO R3 and , in addition, SRAM has been upgraded from 2kB to 32kB, and flash memory from 32kB to 256kB to support more complex projects.

It turned out the SDIO mode on [Severin]’s card was broken, but accessing it with an Arduino and SPI mode worked. There was finally hope to get files off this damaged card.