Most CPU's are based on the same technology as 1970's microprocessors in terms of how external devices are talked to, either memory mapping, or I/O via (very slow) ports. But in the days of the Big Iron Mainframes, Channel Architecture was the best way of transferring data.
It would seem that CPU's today don't follow that path, Sure there is bus mastering DMA, but that is far from Channel Architecture, it's more of "Channel Extension"
Are there any Computers / Systems designed circa this Millennium that follow a Channel Arch?