I forgot to add, the PPC chip does have both internal and external memory, I just am wondering if the bootloader and OS are on the external flash, or if the bootloader is internal and the OS external? I am thinking that it is the case.
the MPC8533E in the Delta and Dell have no internal memory, the storage is a directly connected NAND IC that stores both the OS and bootloader. It's the standard powerPC "bottom boot" that boots from the last ~1MB of flash. PDF here: https://www.nxp.com/docs/en/product-brief/MPC8533EPB.pdf
you really need a JTAG unit designed for newer PPC units that understand how to open (at the minimum) a 1MB window to directly attached NAND. If you're patient you can get ahold of BDI2000's for ~$50