sdhc – liutyi.info

Reading some old posts:

SanDisk Extreme 30 MB/s SD Card
SanDisk SDDR-199
SD Cards test with SDDR-1999

Now I know what was wrong with 30MB/s SanDisk Extreme SD cards. 30 MB/s was not standard bus speed for SD. So it is seems like only (one?) card reader from SanDisk was supporting that speed. And it was not a good idea to buy 30MB/s cards. Actually theoretical maximum speed for normal and high speed SD cards was 12.5 MB/s and 25MB/s (read as 10MB/s and 20 MB/s in real life). And, by the way, USB 2.0 (480 Mbit/s) has reallife speed for cardreader/hdd/etc ~ 30 MB/s at maximum.

New SD card standards are UHS-1 with 50 MB/s and 100 MB/s (read as 45 MB/s and 90 MB/s) and UHS-II with 156 MB/s and 312 MB/s.

So now some examples of UHS-1 standard in use:

SanDisk ImageMate SDDR-289 (USB 3.0)

SanDisk 16 GB UHS-1 45MB/s

USB 2.0 is not enough to get 45+ MB/s that is why UHS-* cardreaders must be USB 3.0 or other modern high speed interface.

Card formated to exFAT. Cardreaders setting “optimized for performance” in Windows 7.

USB	Reader	Card	Read MB/s	Write MB/s
USB 3.0	UHS-1	UHS-1 45MB/s	39MB/s	24MB/s
USB 2.0	UHS-1	UHS-1 45MB/s	26MB/s	16MB/s
USB 2.0	non UHS-1	UHS-1 45MB/s	18MB/s	14MB/s

Card Formatted to FAT32 by SD Formatter 3.1

USB	Reader	Card	Read MB/s	Write MB/s
USB 3.0	UHS-1	UHS-1 45MB/s	36MB/s	32MB/s
USB 2.0	UHS-1	UHS-1 45MB/s	25MB/s	20MB/s
USB 2.0	non UHS-1	UHS-1 45MB/s	18MB/s	17MB/s

speed tested with Flash Memory Toolkit “File Transfer (5MB)”


Sequential Read (MB/s)	52.090	88.012	46.786
Sequential Write (MB/s)	14.136	38.338	42.927
Random Read 512KB (MB/s)	44.635	69.408	40.880
Random Write 512KB (MB/s)	0.659	13.426	29.822
Random Read 4KB (QD=1) (MB/s)	2.818	2.540	3.031
Random Write 4KB (QD=1) (MB/s)	1.077	0.509	1.600
Random Read 4KB (QD=32) (MB/s)	2.825	2.736	2.877
Random Write 4KB (QD=32) (MB/s)	0.852	0.423	1.529