Well, I can't prove it, but I'm pretty sure my problem is on the desktop end.

Summary:

On my laptop (1.4R), ray0 probes and appears to work, either under PCMCIA or
CardBus.  Either way, it configures, detects correctly, and receives ARP
packets from the other system.

On my desktop, it's much harder.  I need to allocate 64K of memory for the
cardbus device.  My BIOS lets me do this starting anywhere from c0000 to dc000
in 0x4000 steps.  If I overlap d4000 through dc000, my PCI SCSI controller
never does its BIOS initialization.

If I select 64k starting at dc000, and configure a kernel this way, the card
configures, probes correctly, and is able to send ARP packets to the laptop,
but I never see the responses.

If I select 64k starting at c0000, and configure the kernel for c0000, I don't
probe the pcic successfully.

If I select 64k starting at c0000, and configure the kernel for c8000, I get
the same results as I do with a "correct" configuration at dc000.

In all cases, I've allocated two IRQ's for ISA devices (in my system BIOS),
and the probe is correctly assigning IRQ9 to the PCIC, and IRQ10 to the ray0.

I'm gonna see if it works if I don't allocate any IRQ's, but I'm pretty
mystified.  This is -current as of today, on both systems.

-s