You need a host controller attached to do DMA, or you're stuck with PIO on a 16-bit bus (PCMCIA mode).
may be the problem is related to the Yenta_CardBus kernel drive, more specifically there is no specific driver for the host controller
it my case it's "Ricoh", and it seems they probably just re-branded some other generic components.
I typed "lspci -v" and looked for the device numbers after "Subsystem: Device" for those device.
Then googled for those device numbers to figure out who actually made the chipsets for the devices.
Unfortunately I have found no good information
anyway, I can explain why the micro drive achieves better performances within the same configuration