The arbiter could take away GNT# at any time. A device that loses GNT# may finish its recent transaction, but may well not commence a person (by asserting FRAME#) Except if it observes GNT# asserted the cycle right before it starts. PCI gives separate memory and memory-mapped I/O port deal https://nathanlabsadvisory.com/nist-800-cyber-security-frame-work/