simo - the chip may be different, but ADFS itself isn't. That's one of the many reasons why ADFS is so slow. The Risc PC can't, AFAICT, support DMA on its internal interface, which is unfortunate.
I've pointed this out before, but there are billions of things you can do to ADFS to bring it up to date, and DMA transfers is a big one on a system that supports them. Creating a filesystem which uses DMA is itself not too difficult.
Filecore is a major bottleneck too - you can't, for example, command cache correctly using filecore, and the way it currently does its sector requests is pretty inefficient when compared to ATA or SCSI specs.
But that's a MUCH meatier job. Anyone who plays with Filecore though is incredibly brave. Or stupid. Or both. After all, it's possible, but much trickier, to cause data corruption in ADFS. Trashing a hard disc by modifying filecore is no doubt easy-peasy .