Corrections re: PCMCIA/PC Card/CardBus/PCI/etc.

From: Erik Walthinsen (
Date: 2002-03-15 08:49:28 UTC

On Thu, 2002-03-14 at 23:32, Christopher Hart wrote:
> (Ricoh Co Ltd RL5c475 pci cardbus bridge and a DWL-650 pcmcia card).

I just want to point out something that I've been learning the hard way for a couple months now. Just because an adapter is a PCI card does *not* mean it is CardBus. I've been hunting for some kind of adapter that will run the Proxim RangeLAN-DS cards I have, which is difficult because the cards only work at 3.3v.

I have the Ricoh adapter you have in my hand right now, and it's most definitely not CardBus. We also have a TI PCI1410-based adapter that is also not CardBus, despite being PCI.

CardBus is a PCI-based bus, which is why the cards look different. The extra gold-colored grounding straps on the card are in fact almost the only ground pins on the whole connector, because the old PCMCIA ground pins have been replaced with signal pins. This is 100% proof of a CardBus card. Any adapter that claims to be CardBus will show a series of spring grounding pads, as seen in the metal shield in this picture:

The specific issue I've been dealing with re: 3.3v PCMCIA adapters is that no one makes them. Nominally, the "PC Card 2.2" specification requires (afaik) that the slot be able to provide both the normal 5v and the lower 3.3v. However, I have yet to find a single card that is not actually CardBus anyway that has 3.3v, or is keyed for 3.3v cards. Even the PCI1410-based card does not work, even though the PCI1410 itself is a 3.3v chip and there's a regulator on the board. The upper-right corner of the Ricoh board in fact has a spot for a regulator, if it were actually a CardBus adapter.

If you actually need 3.3v, you must make sure that the socket is actually keyed for it. The left edge of a PCMCIA/CardBus card (looking into the slot) has a key for either 5v or 3.3v. If the protrusion is about 1/3 the thickness, it's 5v. If it's 2/3, it's a 3.3v-*only* card. Inconveniently enough, the key in the slot is buried deep where you can't see it sometimes even with enough light and the right angle.

I even spent a significant amount of time trying to coax any kind of real information out of SCM, who makes all sorts of PCMCIA/CardBus adapters. They couldn't figure out whether their own product would handle 3.3v cards. Even the engineer really had no clue.

The moral of all this is that you cannot trust *anything* any marketing materials or vendor tells you about card, even if they claim it's a CardBus adapter. Look very carefully at the adapter, see if there's a regulator, see if the slots are CardBus or not, and lastly actually try it out and see if it will work.

I'm very tempted to create a wiki page listing all known details about various adapters...

      Erik Walthinsen <> - System Administrator
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