The embodiments relate to dynamically re-allocating lanes of a computer bus. A computer system having a processor in communication with a module is booted. Allocation of lanes among adapters in communication with connectors of the computer bus is controlled at boot-time and, in response to detection of an additional adapter received after boot-time, an additional allocation of lanes to the additional adapter is dynamically controlled. The additional allocation includes allocating unallocated lanes to the additional adapter, and re-allocating at least one lane from the initial allocation in response to the unallocated lanes being insufficient.