I reloaded an old, pre-toolchain backup (ie. gcc-4.1) with the 184.108.40.206-rt15 kernel and retested kino. Got no dropped frames, I mean none! Looks like data was being written to the HD continuously, instead of in bursts. Unfortunately, 2.6.26-8-rt15 will compile under the new toolchain and boot, but it can't find and mount the root filesystem and panics.
I did notice that the default ext3 journaling mode has been changed to writeback instead of ordered. Changing the journaling mode to ordered data, using the 220.127.116.11-rt14 kernel (fully updated system) greatly helps the kino problem, because data is written to the HD at fixed intervals instead of relying on the system's sync. Overall performance still does not equal that of the older system. Problem is that I can't tell if it's the kernel, toolchain or ext3 code changes that have degraded performance. Do any of you guru's out there have an opinion or suggestions about this?
(PS - it's not the scheduler - changing between the various schedulers does not affect file write results noticably.)