Sign in to follow this  
RyanH

Understanding ExpressCard

Recommended Posts

Hi,

I just had a quick question about expresscards, which are becoming more and more common nowadays. I read that:

"All ExpressCard slots accommodate modules designed to use either Universal Serial Bus (USB*) 2.0, or the emerging PCI*Express standards."

Does this mean that ExpressCard slot itself is connected to the motherboard through both a USB 2.0 interface and a PCI*Express interface and that depending on which slot the card that you purchased is fitted for, it can connect to the necessary interface? Or is it that the manufacturer of the motherboard can decided whether to allow the ExpressCard to connect through USB 2.0 or PCI*Express, depending on if he wants a cheaper solution (USB) or a more high-speed solution (PCI*Express)? Thanks for your help.

Share this post


Link to post
Share on other sites

To my knowledge, the ExpressCard slot always connects directly to the PCIe bus. If a peripheral wants to connect via USB, it would plug into a USB port instead. I expect you can get ExpressCard devices that provide extra USB ports, but the ExpressCard device would still act as a USB controller connected via PCIe.

Share this post


Link to post
Share on other sites

Looks like all ExpressCard slots must provide both PCI-e and USB 2 support. Individual modules are likely to only support one or the other.

From the FAQ

"All ExpressCard slots accommodate modules designed to use either Universal Serial Bus (USB*) 2.0, or the emerging PCI*Express standards."

"The ExpressCard interface uses high-speed PCI Express or USB 2.0 serial interfaces through a 26 contact high-performance beam-on-blade connector. "

Share this post


Link to post
Share on other sites

The ExpressCard form factor includes pins that connect to the PCI Express bus as well as the USB.

I have an ExpressCard memory card reader that shows up as a USB device only. It doesn't add a new USB controller, it just shows up as a USB device plugged in to a "Root Hub" the way any USB memory card reader would show up plugged into any other USB port.

This means that for less-needy devices (such as memory card readers,) they can use the ExpressCard slot as an internal USB-connected device, and for more complex devices (such as an eSATA controller or a FireWire 800 controller,) they connect to the PCI Express bus. (It is a PCI Express x1 connection, so it's "only" ~250 MB/s, but someone could design a video card for it, if they really felt like it.)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this