1. A method of updating a basic input/output system (‘BIOS’) boot block security module (‘security module’) in a plurality of compute nodes of a multinode computer, the plurality of compute nodes connected through a scalability bus for operation as a single computer, each compute node comprising a reset control module for controlling propagation of reset signals among the compute nodes through the scalability bus, the method comprising: for each compute node in the multinode computer, upon powering on the compute node: determining, by the security module of the compute node, whether a new image of security module is available; if a new image of the security module is available, commanding, by the security module, the reset control module of the compute node to block an attempt by the security module to propagate a reset signal on the scalability bus to other compute nodes in the multinode computer; updating, by the security module, to the new image of the security module; upon completion of the update, resetting, by the security module, the compute node including attempting to propagate a reset signal on the scalability bus to other compute nodes in the multinode computer; and blocking, by the reset control module, the attempt to propagate the reset signal on the salability bus.