SDHC is SD with High Capacity

SDHC® is the new designation for Secure Digital cards exceeding 2GB in size. The HC series adheres to the SD Specification Version 2 which allows the cards to reach 32GB in size.

Aside from the larger storage capacity, SDHC cards offer optimized recording performance with support for FAT32 file formats. The SD Association has defined 3 speed classes in order to identify speed and performance capabilities of the SD/SDHC cards and the host products. The SD speed Class Ratings specify the minimum sustained write speed for SDHC cards, as follows:

Class 2 : 2 MB/s
Class 4 : 4 MB/s
Class 6 : 6 MB/s*

SDHC-compliant cards have both the SDHC and Speed Class logo in their packaging.



Though SDHC cards are identical in size with the standard SD card, only SDHC-compatible products will be able to accept the newer SDHC cards. SDHC host products can use both SD and SDHC memory cards, while SD host products can use only SD memory cards of 2GB or lesser size.

*1 megabyte (MB) = 1 million bytes
Note: SDHC, the SDHC logo and SD are trademarks

SE Phone - MS Duo Compatibility

Phone Model	Card
P800 · P900 · S700i · S710a · SO505i · SO505iS · Z1010	MS Duo
A5404S · K750i · P910i · P990i · SO506iC · W800i · W900i · V800	MS Pro Duo

Nokia - MMC Compatibility

Phone Model	Card
3300 • 3600 • 3620 • 3650 • 3660	MMC
6225i • 6230 • 6230i • 6255i • 6260 • 6600 • 6620	MMC
7710 • 9000 • 9110 • 9210 • 9500 • 9210i • 9500	MMC
Ngage • Ngage QD	MMC
3230 • 6670 • 7610	RSMMC
6630 • 6680 • 6681 • N70 • N72 • N90	DV RSMMC
6270 • 6280 • N71 • N73 • N80 • N92 • N93 • E61	miniSD
3250 • 6131	microSD

Measuring MMC Speed

Multimedia Card (MMC) is the type of flash card popularly used in Nokia phones. As of this writing, aside from the Nokia 6270 which uses mini-SD, the rest can accept only MMC or its variants (reduced-size, dual-voltage).

I use Sisoftware’s Sandra (System ANalyser, Diagnostic and Reporting Assistant) to measure the speed of my flash cards. You can download Sandra here.

You would need a USB card reader to make the flash card accessible to your computer. Once plugged in, Windows XP should automatically load the required driver and show your flash card as one of the available drives.

Select the module Removable Storage/Flash Benchmark and indicate the drive corresponding to the flash card. Sandra will measure the read, write and delete performance of your card using file sizes of 512B, 32kB, 256kB, 2MB, and 64MB. Performance ratings are expressed in operations per minute and kB per second.

Whereas most vendors use the equivalence of 1X=150kBps, take note that Sandra uses 176kBps. To get the standard benchmark rating, multiply the Sandra X-rating by 176/150 or 1.17.

Flash Card Speed Rating - The X-factor

You may have noticed that some flash cards, notably Compact Flash and Secure Digital, have X-ratings emblazoned on their packaging. Just like in the optical drive industry, the X-ratings give a measure of how fast the device can handle data.

So how fast really is a 133x SD card? A 1x speed rating corresponds to a transfer rate of 150 kilobytes (KB) per second, so a flash card rated at 133x can attain speeds of around 20 megabytes (MB) per second.

Some vendors use different names for their high-speed flash cards. Kingston labels their higher speed SD as Elite Pro SD (45x-50x) and SD Ultimate (120x-133x). On the other hand, Sandisk has their Ultra II SD (10MBps read/9MBps write) and Extreme III series (20MBps).

Now, tell me, what is the equivalent X-rating of a Sandisk Ultra II SD?