How do I turn off "preemption" (getting "TIMEOUT - WRITE_DMA")

[bsdfsse]

I am getting "TIMEOUT - WRITE_DMA" messages on my ad2 and ad3 
hard-drives.  I never get them on ad0 or the CD drive.  I did some 
searching, and it sounds like I need to turn of "preemption" in the 
kernel.  I'm running 5.3-BETA4 on the computer.

I am going to guess this is turned on for the beta-testing.

Any ideas?  I just started running 5.x last night.  %-)

thx!