  The achievable acquisition rates of modern triggered nuclear physics
experiments are heavily dependent on the readout software, in addition to the
limits given by the utilized hardware. This paper presents an asynchronous
readout scheme that significantly improves the livetime of an otherwise
synchronous triggered VME-based data acquisition system. A detailed performance
analysis of this and other readout schemes, in terms of the basic data transfer
operations, is described. The performance of the newly developed scheme as well
as synchronous schemes on two systems has been measured. The measurements show
excellent agreement with the detailed description. For the second system, which
previously used a synchronous readout, the deadtime ratio is at a 20 kHz
trigger request frequency reduced by 30 % compared to the nearest contender,
allowing 10 % more events to be recorded in the same time. The interaction
between the network and readout tasks for single-core processors is also
investigated. A livetime ratio loss of a few percent can be observed, depending
on the size of the data chunks given to the operating system kernel for network
transfer. With appropriately chosen chunk size, the effect can be mitigated.
