In Figure 1, the TCW points to the virtual address of a TIDAL. The TIDAWs within the TIDAL point either to storage areas that larger than 4K or to storage areas that cross page boundaries. The TIDAL itself also crosses a page boundary. Note that for EXCPVR requests, this would not be allowed because it violates I/O architecture rules. However, for EXCP requests, the virtual TIDAL may have any alignment and may cross page boundaries - EXCP will translate the virtual TIDAL to a real TIDAL and ensure proper alignment and ensure that page boundaries are not crossed.