For a long time, there were exactly three cards available: SONY MS PRO-HG Duo as 1GB MS-EX1G, 2GB MS-EX2G and 4GB MS-EX4G.
SanDisk was involved in the original press release from December 2006 announcing the MS PRO-HG, but it took until May 2008 until they announced the first series. Although their Extreme IV line with 40MB/s read/write would be the appropriate speed range, the first series will be the SanDisk Extreme III Memory Stick PRO-HG Duo as 4GB SDMSHX3-004G-A31 and 8GB SDMSHX3-008G-A31 with a claimed read/write speed of 30MB/s.
As of June 2008, that makes a total of five cards available, with sizes from 1GB to 8GB.
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Memory Stick PRO-HG will currently be available in Duo size only. Compared to the Memory Stick PRO, the maximum clock rate is raised from 40MHz to 60MHz, while the bus width is doubled from 4bit to 8bit. This is done by using longer pads of about 6.3mm length instead of about 4.8mm length. The previous four data pads are then split up in a front half and a rear half to double the bus width. These two measures raise the theoretical data rate from 19MB/s to 57MB/s.
The Memory Stick PRO-HG will be fully compatible with existing Memory Stick PRO devices at up to 40MHz and 4bit bus width. This means that a Memory Stick PRO-HG will act exactly as a regular Memory Stick PRO when used with a decive that is not aware of the Memory Stick PRO-HG standard.
While all previous ExpressCard based Card Readers only used the USB 2.0 link of the ExpressCard interface, the SONY MSAC-EX1 is a true PCIe x1 adapter with a theroretical bandwidth of about 238MB/s.
The adapter identifies as "Sony Memory Stick Duo ExpressCard Adaptor", shows up as PCI device PCI\VEN_104D&DEV_8211&REV_00, and is handled by the service "SonyEXMS" using SonyEXMS.sys.
While the SONY Memory Stick PRO previously stayed well behind the SanDisk models, the new SONY Memory Stick PRO-HG Duo claim data rates of 30MB/s.
For PRO-HG, SanDisk upgraded the Extreme III line from slightly overrated 18MB/s to claimed 30MB/s.
For details regarding the maximum performance of the card, see the SDMSHX3 Page .
Of course, Memory Stick PRO-HG can be read with any Memory Stick PRO device. Tests with current card readers without MS PRO-HG support showed read rates of about 16MB/s and write rates of about 14MB/s.