Abstract: A method and apparatus for generating identification numbers for PCI Express that provides unique generation and substantially increased system performance. A system having a PCI Express fabric and PCI devices connected thereto generates unique TAG identification numbers for transactions with substantially increased performance. The system generates and prepares up to three available TAG IDs in advance, before a request is granted. When a completion-required request receives a grant, it picks up the TAG ID from the storage rather than generating it on the fly. This enables the system to process back-to-back TLP requests without any dead cycles.