The Serial ATA specification defines a new capability that has no equivalent in the parallel ATA standard. Referred to as first-party direct memory access (or just first-party DMA), the new capability has no parallel ATA equivalent, and none of the existing parallel ATA commands make use of first-party DMA or rely on it. No use for the capability was defined in the Serial ATA specification. Instead, the facility was included in the specification as a forward-looking feature to accommodate anticipated new uses and capabilities. One of the first capabilities added to Serial ATA in the subsequent Serial ATA II specification made use of the first-party DMA facility that was defined in the 1.0 specification.

Before delving into the details of the first-party DMA mechanism, its function, and its inner workings, you might review the traditional direct memory access (DMA) model for ATA by reading the next section. If you already know it well, you might skip over ATA DMA Model to the firstparty DMA facility detailed review along with associated implementation considerations, in First-Party DMA Model. Some applications and potential uses of the facility that are described in the following sections serve to illustrate the utility of the flexible mechanism, including one specific application of first-party DMA as utilized in the follow-on Serial ATA II specification.