Whether or not SCSI TCQ causes massive interrupt overhead depends on the bus being used to connect the SCSI host bus adapter. On Conventional PCI, PCI-X, PCI Express, and other buses that permit it, first party DMA allows for low interrupt overhead. The older ISA bus required a SCSI host adapter to generate an interrupt to cause the CPU to program the third-party DMA engine to perform a transfer, and then required another interrupt to notify the CPU that a task in the queue was finished, causing high CPU overhead.