SCB_64_BTT
scbid = ahc_inb(ahc, SCB_64_BTT + TCL_TARGET_OFFSET(tcl));
ahc_outb(ahc, SCB_64_BTT+TCL_TARGET_OFFSET(tcl), SCB_LIST_NULL);
ahc_outb(ahc, SCB_64_BTT + TCL_TARGET_OFFSET(tcl), scbid);