I have some piece of code, which is a driver for a proprietary
PCI device. We were running that code on VxWorks 5.5.1 and the
interrupt stack usage was 1028 bytes. We switched to VxWorks
6.3 (BSP, compiler, tool chains), and the interrupt stack usage has
climbed to more than 9000 bytes.

The target is an MPC 8560. Any pointers on why this would be
the case ? As in, are there compiler options that have changed
which would affect the stack usage significantly ? Any others
pointers would be helpful.