To be specific, the results I get are:
(dd iflag=direct if=/dev/mmcblk1 of=/dev/null bs=4M count=256)
read 96 MHz 8-bit: 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 12.9219 s, 83.1 MB/s
read 96 MHz 8-bit: 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 12.9004 s, 83.2 MB/s
read 128 MHz 8-bit...