Nokia-N900:~# time dd if=/dev/mmcblk1p1 of=/dev/null bs=1M count=500
500+0 records in
500+0 records out
real	0m 33.72s
user	0m 0.00s
sys	0m 5.82s
Nokia-N900:~# time dd if=/dev/mmcblk0p1 of=/dev/null bs=1M count=500
500+0 records in
500+0 records out
real	0m 26.67s
user	0m 0.01s
sys	0m 6.47s