Md0u80c9: When I said "driver issue" I meant that in the sense of it having nothing to do with the OS itself. And I'm sure some of the IDE podules could do something akin to it if the hardware did support it. Most people also seem to forget that ADFS is not a file system - it's the IDE driver for the motherboard's onboard controller. I also wasn't saying UDMA could be implemented in ADFS for RiscPCs. Because it can't. But it could be in one of the various flavours of IDEFS.
Filecore needs rewriting. It utterly sucks compared to any modern file system these days, and has done for some time. The non-reenterancy of it, and its horrible slowness aren't nice either. What might be a nice idea is a new Filecore that acts as a proxy for other modules providing different file systems, so you could use all the current ADFS/IDEFS/ATAFS/etc drivers, and yet still have a choice of file system to run on top of them.