Memory Cards

All storage products will display a lower than stated memory capacity. The reason is the general used method for calculation of megabyte used by manufacturers:

The calculation for a 32GB is done like this:

32GB=32.000.000.000 Bytes, 1024Byte = 1KB

32.000.000.000/1024= 30.250.000KB, 1024KB=1MB

31.250.000.000/1024= 30.517,58MB, 1024MB=1GB

30.517,58/1024= 29,8GB

Therefore a 32GB Flash Disk will show 29,8GB under Windows.

SDHC (Secure Digital High Capacity, SD 2.0) is an extension of the SD standard which increases card's storage capacity up to 32 GB. SDHC cards share the same physical and electrical form factor as the older SD cards, allowing SDHC-devices to support both newer SDHC cards and older SD-cards. To increase addressable storage, SDHC uses sector addressing instead of byte addressing in the previous SD standard. The SD 2.0 standard limits the maximum capacity of an SDHC card to 32 GB. SDHC cards will not work in devices designed to the older SD 1.x specification. The SDHC trademark is licensed to ensure compatibility.

The Secure Digital Extended Capacity (SDXC) format was unveiled at CES 2009. The maximum capacity defined for SDXC cards is 2 TB (2048 GB). The older SDHC cards also have a maximum capacity of 2 TB based on the card data structures, but this is artificially limited to 32 GB by the SD 2.0 specification. The first SDXC being released are governed by an SD 3.0 specification (which also still specifies FAT32 format and thus lower capacities), whereas higher capacity and faster SDXC are expected to follow an SD 4.0 specification, which is due to be released in the spring of 2010.

The speed class rating is the official unit of speed measurement for SDHC cards, which were defined by the SD Association. It is equal to 8 Mbit/s, and it measures the minimum write speeds based on the best fragmented state where no memory unit is occupied.

The following are the ratings of some currently available cards:

• Class 2: 16 Mbit/s (2 MB/s)
• Class 4: 32 Mbit/s (4 MB/s)
• Class 6: 48 Mbit/s (6 MB/s)
• Class 10: 80 Mbit/s (10 MB/s)

Pretec provide the highest speed SDHC 233x pro class 16 card. It's read/write performance up to 35/20 MB/s.

In Pretec CF card product definitions, 1x represent the performance of 150KBytes/sec. Take the 433x CF card as an example, the performance is 65MB/s (433 x 150KBytes/sec=65MBytes/sec).

All data transfer statistics provided is for your reference only. The actual speed of data transfer speed will depend on different system specifications, settings and performance.

There are three subdivisions of CF cards, Type I cards, the thicker Type II cards and the I/O cards.

CF Type I

At 43mm (1.7") x 36mm (1.4") x 3.3mm (0.13"), the CF Type I card's is less than one-half of a current PCMCIA Type II card. Compared to a 68-pin PCMCIA card, a CF card has 50 pins but still conforms to ATA specs.

CF Type II

At 43mm (1.7") x 36mm (1.4") x 5.5mm (0.19"), the CF Type II card's is equal to that of a current PCMCIA Type II card. Compared to a 68-pin PCMCIA card, a CF card has 50 pins but still conforms to ATA specs.