Label on packaging:

Class 6 Read: Max 24MB/s Write: Max 13 MB/s

Label on Card:

front (red): 8 GB

back: MB-SS8GA MBSS8GVCDBCA-RF D OLX00000 1 4 7 MADE IN KOREA DESIGNED BY SAMSUNG

head /sys/block/mmcblk0/device/* ==> /sys/block/mmcblk0/device/cid <== 1b534d3030303030100b6b930300bc00 ==> /sys/block/mmcblk0/device/csd <== 400e00325b5900003b577f800a400000 ==> /sys/block/mmcblk0/device/date <== 12/2011 ==> /sys/block/mmcblk0/device/erase_size <== 512 ==> /sys/block/mmcblk0/device/fwrev <== 0x0 ==> /sys/block/mmcblk0/device/hwrev <== 0x1 ==> /sys/block/mmcblk0/device/manfid <== 0x00001b ==> /sys/block/mmcblk0/device/name <== 00000 ==> /sys/block/mmcblk0/device/oemid <== 0x534d ==> /sys/block/mmcblk0/device/preferred_erase_size <== 4194304 ==> /sys/block/mmcblk0/device/scr <== 0235800000000000 ==> /sys/block/mmcblk0/device/serial <== 0x0b6b9303 ==> /sys/block/mmcblk0/device/type <== SD ==> /sys/block/mmcblk0/device/uevent <== DRIVER=mmcblk MMC_TYPE=SD MMC_NAME=00000 MODALIAS=mmc:block

Disk /dev/mmcblk0: 7964 MB, 7964983296 bytes 91 heads, 18 sectors/track, 9497 cylinders, total 15556608 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/mmcblk0p1 8192 15556607 7774208 b W95 FAT32

$ factor 7964983296 7964983296: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 211

$ sudo ./flashbench -a /dev/mmcblk0 --blocksize=1024 align 805306368 pre 813µs on 1.03ms post 694µs diff 274µs align 536870912 pre 841µs on 1.1ms post 772µs diff 295µs align 402653184 pre 788µs on 1.06ms post 710µs diff 312µs align 268435456 pre 805µs on 1.09ms post 772µs diff 303µs align 201326592 pre 794µs on 1.05ms post 691µs diff 311µs align 134217728 pre 851µs on 1.1ms post 771µs diff 288µs align 100663296 pre 794µs on 1.05ms post 695µs diff 303µs align 67108864 pre 852µs on 1.11ms post 779µs diff 293µs align 50331648 pre 793µs on 1.05ms post 695µs diff 307µs align 33554432 pre 850µs on 1.1ms post 772µs diff 292µs align 25165824 pre 794µs on 1.05ms post 693µs diff 309µs align 16777216 pre 855µs on 1.11ms post 782µs diff 288µs align 12582912 pre 755µs on 1.03ms post 695µs diff 302µs align 8388608 pre 798µs on 1.08ms post 777µs diff 296µs align 6291456 pre 726µs on 1.01ms post 718µs diff 287µs align 4194304 pre 705µs on 939µs post 734µs diff 219µs align 3145728 pre 619µs on 715µs post 716µs diff 47.2µs align 2097152 pre 687µs on 922µs post 721µs diff 218µs align 1572864 pre 621µs on 711µs post 715µs diff 43.5µs align 1048576 pre 615µs on 724µs post 729µs diff 51.9µs align 786432 pre 620µs on 714µs post 715µs diff 46.9µs align 524288 pre 610µs on 712µs post 725µs diff 44.4µs align 393216 pre 620µs on 714µs post 710µs diff 49.2µs align 262144 pre 616µs on 719µs post 724µs diff 48.5µs align 196608 pre 619µs on 712µs post 713µs diff 46.2µs align 131072 pre 614µs on 711µs post 722µs diff 42.4µs align 98304 pre 615µs on 705µs post 714µs diff 40.7µs align 65536 pre 614µs on 712µs post 723µs diff 43.7µs align 49152 pre 614µs on 697µs post 709µs diff 35.5µs align 32768 pre 615µs on 712µs post 710µs diff 49.5µs align 24576 pre 617µs on 702µs post 715µs diff 35.8µs align 16384 pre 617µs on 702µs post 716µs diff 35.7µs align 12288 pre 678µs on 668µs post 659µs diff -688ns align 8192 pre 617µs on 710µs post 717µs diff 43.1µs align 6144 pre 647µs on 642µs post 635µs diff 1.09µs align 4096 pre 677µs on 671µs post 662µs diff 1.85µs align 3072 pre 691µs on 686µs post 672µs diff 4.76µs align 2048 pre 705µs on 701µs post 691µs diff 2.92µs

# Trying 2 MB erase size (not likely) $ sudo ./flashbench --open-au /dev/mmcblk0 --blocksize=1024 --erasesize=$[1024*1024*2] 2MiB 6.64M/s 1MiB 3.37M/s 512KiB 2.76M/s 256KiB 2.7M/s 128KiB 3.12M/s 64KiB 3.12M/s 32KiB 2.75M/s 16KiB 2.33M/s 8KiB 1.98M/s 4KiB 981K/s 2KiB 420K/s 1KiB 211K/s

# trying 6 MB erase size (looks right) $ sudo ./flashbench --open-au /dev/mmcblk0 --blocksize=$[3*8192] --erasesize=$[6*1024*1024] 12MiB 8.03M/s 6MiB 7.99M/s 3MiB 7.99M/s 1.5MiB 7.98M/s 768KiB 8.03M/s 384KiB 7.78M/s 192KiB 8M/s 96KiB 6.85M/s 48KiB 6.32M/s 24KiB 4.27M/s

# trying 8 MB erase size (supports 6 MB theory) $ sudo ./flashbench --open-au /dev/mmcblk0 --blocksize=$[8192] --erasesize=$[8*1024*1024*2] 16MiB 6.77M/s 8MiB 5.81M/s 4MiB 5.76M/s 2MiB 5.75M/s 1MiB 5.76M/s 512KiB 5.77M/s 256KiB 5.74M/s 128KiB 5.74M/s 64KiB 5.7M/s 32KiB 4.24M/s 16KiB 2.15M/s 8KiB 1.29M/s

# Countertest with 3 MB blocks: $ sudo ./flashbench --open-au /dev/mmcblk0 --blocksize=$[3*8192] --erasesize=$[3*1024*1024] --open-au-nr=2 3MiB 4.55M/s 1.5MiB 4.53M/s 768KiB 4.55M/s 384KiB 4.55M/s 192KiB 4.53M/s 96KiB 4.14M/s 48KiB 3.94M/s 24KiB 2.99M/s

# one 6 MB block, random access, not good: $ sudo ./flashbench --open-au /dev/mmcblk0 --blocksize=$[3*8192] --erasesize=$[6*1024*1024] --random 6MiB 7.95M/s 3MiB 5.7M/s 1.5MiB 5.07M/s 768KiB 2M/s 384KiB 1.12M/s 192KiB 509K/s 96KiB 243K/s 48KiB 175K/s 24KiB 175K/s

# trying two blocks of 6 MB linear instead, works fine: 6MiB 7.86M/s 3MiB 8.01M/s 1.5MiB 8.03M/s 768KiB 8.01M/s 384KiB 8.03M/s 192KiB 8.02M/s 96KiB 6.87M/s 48KiB 6.33M/s 24KiB 4.3M/s

# Three blocks fail: $ sudo ./flashbench --open-au /dev/mmcblk0 --blocksize=$[3*8192] --erasesize=$[6*1024*1024] --open-au-nr=3 6MiB 8.02M/s 3MiB 5.28M/s 1.5MiB 3.05M/s 768KiB 2.35M/s 384KiB 1.64M/s 192KiB 1.55M/s 96KiB 1.14M/s 48KiB 1.15M/s 24KiB 1.12M/s

# Four blocks fail in a worse manner: $ sudo ./flashbench --open-au /dev/mmcblk0 --blocksize=$[3*8192] --erasesize=$[6*1024*1024] --open-au-nr=4 6MiB 5.29M/s 3MiB 5.08M/s 1.5MiB 2.77M/s 768KiB 1.26M/s 384KiB 648K/s ^C