expresscard

[Vypr]

I remember when I bought my X60s back in Feb of last year, the catalog with the list of all the models and the features listed the X60 as having an ExpressCard via an adapter. Has such an adapter ever been released or can you simply just plug in an ExpressCard device?

[lev]

I remember when I bought my X60s back in Feb of last year, the catalog with the list of all the models and the features listed the X60 as having an ExpressCard via an adapter. Has such an adapter ever been released or can you simply just plug in an ExpressCard device?

My understanding is that the correct interpretation of this statement is that the card slot implements the CardBay standard, as defined in a clause added to the PC Card specification by the PCMCIA in the 8.0 (April 2001) release. This standard adds support for USB signalling (it was originally going to also incorporate pins for IEEE 1394 aka firewire, but in the end they stopped short and just marked out a set of pins as reserved for implementing 1394 in a possible future standard, a standard which we now know will never come), and was at the time intended to allow peripheral manufacturers to use the same chipsets for both their USB/firewire peripherals, and their PC cards. When ExpressCard came along, CardBay was briefly hailed as the way to smooth the transition to ExpressCard. The thinking was that all the relevant signals would be present in the slot, and since the ExpressCard/34 device is somewhat smaller than PC Card, it should be straightforward to offer a simple physical passive adapter (ie one that just connects the right pins across, with no active electronics) between the two formats. See eg Dell's 2003 whitepaper This would only work for ExpressCard/34 cards who use the only the USB 2.0 connection of ExpressCard, and not the PCI express x1 lane. However, while several manufacturers started implementing CardBay slots, I'm not aware of any cards that make use of the cardbay functionality, and while there have been many rumours of this fabled passive adapter, to my knowledge no general-purpose one has been produced.

The only thing which comes close to being this passive adapter is the one which ships alongside Novatel's v640 ExpressCard EVDO adapter. However, this is a) only intended to work with the v640, b) only specified to work with Ti or O2 smart cardbus controllers (ie not the Ricoh controller used in the X60 series) (btw I don't understand the reasoning for this) and c) has been widely reported to not work very well, even in the cases where it is supposed to be OK (see eg this thread). Just recently there has been released an active adapter, which is reported compatible with cardbus and cardbay, all chipsets. Instead of wiring through the cardbay's USB pins it implements it's own PC-card format USB host controller on the PCI bus. Due to these additional electronics it's a bit larger (and more expensive), and will poke out of the side of the notebook a quarter-inch or so, but it's reported to work well. This adapter is also from Novatel, and here's one place selling it

Also, to go the other way (from expresscard to carbus) there is this bad boy which has been under development for a long time, and was supposed to be released some time last year, so it's not clear what is happening with it. There are also (expensive) cardbus adapters that you can plug into a USB socket on your laptop such as this one.

HTH,
Lev

[tomh009]

Wow ... that was a great explanation!

So do I understand correctly that ExpressCard/34 and ExpressCard/54 aren't actually electrically equivalent, and the /34 version (which is the only one available on the MacBooks) is significantly slower than the /54?

[lev]

Wow ... that was a great explanation!

So do I understand correctly that ExpressCard/34 and ExpressCard/54 aren't actually electrically equivalent, and the /34 version (which is the only one available on the MacBooks) is significantly slower than the /54?

You do not understand correctly.

ExpressCard/34 and ExpressCard/54 are electrically equivalent. It's just a matter of the size of the slot, a bit like how the difference between PC Card Types I/II/III is just the thickness. You can put a /34 in a /54 socket but not the other way around, (also, the Dell whitepaper I linked before mentions the possibility of 68mm slots that have room for either two /34s or one /54 but not both at once. However I don't believe these actually exist).

The reasons you would build a card in the /54 format rather than /34 is: you need the extra space for all your electronics, or you need the extra area for thermal dissipation, or you need the extra space in order to have more space for a plug-in device. The last is the most important one, and in fact the main users of the /54 card format currently are CompactFlash adapters (CompactFlash is 43mm wide, so it wouldn't fit in a /34 slot). (Apple's choice to use /34 instead of /54 is thus mainly only an issue for pro-photographers using digital SLRs which take CF).

Every ExpressCard socket, whether /34 or /54, has connections for both USB 2.0 and a PCI express x1 lane (in addition to power, card detect, wake-up-the-computer (eg network cards doing wake-on-lan) and sundry others). However, ExpressCard card builders get a choice whether to use the USB or the PCIe functionality (or even both at the same time). They'll go with USB when they want a cheap, low-power implementation, and they'll use PCI express when they need the higher data rate.

It's a sensible standard: PC makers already have USB and PCIe buses in their systems anyway, so it costs little to wire them to the socket; peripheral makers are already making PCI express and USB-based devices, so they just need to put them in a different physical format; OS's already have drivers for USB and PCI express. On top of the USB and PCIe standards, the ExpressCard standard adds specifications for power, thermal, physical dimensions, connectors, and so on.

Anyway, the point I was trying to get across, which mislead you into thinking that /34 has lower data rate available than /54, is that any USB or PC card to ExpressCard adapters can only hope to support those ExpressCard modules that use only the USB connection. These will include things like EVDO radios, serial ports, modems, parallel ports, GPS receivers, flash memory (SD/CF/xD/MMC/etc), Bluetooth, etc. A USB or PC card adapter such as the Novatel one cannot and never will (not enough bandwidth) support ExpressCard cards who use the PCIe connection. These will include gigabit ethernet, 1394, TV tuners, graphics cards, SATA, etc.

[tomh009]

I think the statement that confused me was this one:

This would only work for ExpressCard/34 cards who use the only the USB 2.0 connection of ExpressCard, and not the PCI express x1 lane.

So from your second post, I do now understand that both /34 and /54 had both USB and PCIe connections, and the above was referring to only that subset of /34 cards that use only the USB bus (such as the CardBus adapters. I read it the other way -- that /34 only has USB2 available.

Thanks for the clarification, and the education about ExpressCards!

[lev]

I think the statement that confused me was this one:

This would only work for ExpressCard/34 cards who use the only the USB 2.0 connection of ExpressCard, and not the PCI express x1 lane.

So from your second post, I do now understand that both /34 and /54 had both USB and PCIe connections, and the above was referring to only that subset of /34 cards that use only the USB bus

Yah. Do you think it would have been clearer if I had written this?

This would only work for those ExpressCard/34 cards who use the only the USB 2.0 connection of ExpressCard, and not the PCI express x1 lane.

[tomh009]

Yah. Do you think it would have been clearer if I had written this?

This would only work for those ExpressCard/34 cards who use the only the USB 2.0 connection of ExpressCard, and not the PCI express x1 lane.

I think we are digressing into English grammar here but ...

That's much better, adding the "those" clarifies that it's only some of the /34 cards. Here is a final minor tweak:

This would only work for those ExpressCard/34 cards that use the only the USB 2.0 connection of ExpressCard, and not the PCI express x1 lane.

Again, thanks for the ExpressCard explanation, even if I did get confused for a while!

[Vypr]

I see, thanks for the information.