System memory to video memory SRCCOPY transfers are the most common type of hardware-supported blit operation. Consequently, the most typical use for such an operation is to move textures from a large collection of system memory surfaces to a surface in video memory in preparation for subsequent operations. System-to-video DMA transfers are about as fast as processor-controlled transfers (for example, HEL blits), but are of great utility since they can operate in parallel with the host processor.