In parallel an interrupt signal is asserted. Data-Mover memory provides the bulk storage space required to smooth trigger bursts and data transmission delays. Integrated protocol chips are available and since PCI modules are targeted for a very large market they are expected to be fairly inexpensive. VME modules have been bought to evaluate data-throughput and to start software development. Performance There has been some discussion on the Web regarding the performance of the PPC chip and Motorola PPC-VME boards in particular.
Interrupt latency is an area of concern and it seems that there is some non-deterministic behaviour.
Click here to see results of some external measurements. Our own results basically confirm the observation that the interrupt latency can be as high as 50 us when the network activity is high. The green CPU LEDs change from a constant glow to periodic flashes.