| Joined: | Mon Apr 2nd, 2012 |
| Location: | South Lakeland, UK |
| Posts: | 4066 |
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My understanding is SD and XQD are fundamentally different types of data transmission protocols.
I don't believe that are simply the same thing with different physical interfaces.
From what I can gather the XQD cards use a variation of PCIe, where SD cards use a variation of SATA and CF cards are an implementation of ATA (IDE) protocols. PCIe data transmission is very much faster than SATA and is used to directly access the CPU with bulk data without the intervention of controllers. An example being M2 drives which can transmit data at extremely high data rates like ~2000MB/sec directly to the PCIe bus. The XQD cards may be a variation of the M2 storage in a different form, in which case they are the future.
My (simplistic) understanding is the SD card system in a camera includes a controller to assemble the bit groups into an orderly, managed procession of data. The XQD communication is MUCH simpler and just dumps the raw data from the camera on the host (computer) and lets the potentially more powerful host sort things out to create the appropriate final storage device protocol.
An 'adaptor' would not just be physical, it would need powerful and sophisticated circuitry to control and order the data output to the SD card. This task is normally carried out by an SD card equipped camera.
The underlying reliability and speed of the XQD card would seem to me to rely on relieving the camera from detailed data control tasks, which speeds things up, saves power and is more efficient, tasking the receiving host (computer) to order, control and assemble the data for storage. A task which it's obviously much better equipped, having powerful processors and controllers. It seems this is how the XQD card saves time and can absorb data much quicker because less processing takes place at this stage because it's at PCIe bus level, direct processor, unrefined data.
http://www.dvxuser.com/V6/archive/index.php/t-328503.html
'AtticusLake' seems to know what he (she?) is talking about.
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Robert.