I plugged 32GB Transcend microSDHC Class 10 UHS-I 300x (Premium) card (TS32GUSDU1) in Transcend USB 3.0 Card Reader (TS-RDF5). Since both the card and the reader are UHS-I compatible, I decided to test the rated capability of the card. Also, the card is supposed to deliver its full potential when used in UHS-I host.
Product: 32GB Transcend microSDHC Class 10 UHS-I 300x (Premium) card (TS32GUSDU1)
Size 11mm x 15mm x 1mm Op. Voltage 2.7V~3.6V Op. Temperature - 25°C(- 13°F)~85°C(185°F) Durability 10,000 insertion/removal cycles Weight 0.4g Transfer Rate (Max)* 45MB/s 300x *Note Speed may vary due to host hardware, software and usage.
Dimensions 56mm (L) × 24mm (W) × 8.9mm (H) Weight 18g Interface USB 2.0 / USB 3.0 Slot Power Output 5V Operating Temperature 0°C (32°F)~70°C (158°F) Certificates CE, FCC, BSMI, C-tick, KC Supported Cards SDHC (UHS-I), SDXC (UHS-I), microSDHC (UHS-I), microSDXC (UHS-I) System Requirements Desktop or notebook computer with USB port (USB3.0 port needed for USB3.0 performance) One of the following Operating Systems:
- Windows XP
- Windows Vista
- Windows 7
- Windows 8
- Mac OS 10.2.8 or later
- Linux Kernel 2.6.30 or later
My laptop is running Windows 7 x64 Ultimate SP1 on Intel Core i3 2.27 GHz equipped with 4GB DDR3 RAM and USB 2.0 ports. Benchmarking software was CrystalDiskMark 3.0.3 x64. USB 2.0 can ONLY limit the speed beyond 35 MB/s. According to Wikipedia,
USB 2.0 was released in April 2000 (now called "Hi-Speed"), adding higher maximum signaling rate of 480 Mbit/s or 60 MB/s (due to bus access constraints the effective throughput is limited to 35 MB/s or 280 Mbit/s), in addition to the "USB 1.x Full Speed" signaling rate of 12 Mbit/s
USB 3.0 was released in November 2008. The standard defines a new SuperSpeed mode with a signaling speed of 5 Gbit/s (625 MB/s) and, due to encoding overhead, usable data rate of up to 4 Gbit/s (500 MB/s).
Now, the worse part comes. Since TS-RDF5K supports UHS-I, I presume it acts as an UHS-I host by their definition. Though the card is rated to have a maximum speed of 45 MB/s if UHS-I host is used, in reality it offered 14.6 MB/s, which is way less than what is advertised. Can't blame the usage of USB 2.0 as the practical maximum is 35 MB/s.
Test system: Intel Core i3 2.27 GHz, Windows 7 Ultimate x64, USB 2.0 host, Transcend TS-RDF5 USB 3.0 Adapter, 4 GB DDR3
Test system: Intel Core i3 1.80 GHz, Windows 8.1 x64, USB 3.0 host, Transcend TS-RDF5 USB 3.0 Adapter, 4 GB DDR3