Parallel ATA 4 pin Molex "AMP Mate-n-Lock" power connection provides 5 volts for electronics and 12 volts for drive motors. 40 pin connection between interface card and device. 80 lines (40 extra ground) for faster data transfers. Original protocol targeted hard drive devices. ATAPI - ata packet interface. Additional protocol (commands) that allow controller to work with tape drives, cd and dvd drives, tape drives, large-capacity floppies, and other non-hard drive devices. Based on SCSI control commands and response. Serialized requests - Once a particular task is initialized, the controller/device pair is tied up until done. This is the default for most implementation of PATA. NCQ - native command queueing - supported by protocol but seldom implemented. Would allow 2nd device to be acted on while 1st device is processing previous request. (SCSI protocol). The clock speed for the interface is based on the pc system bus. Original design for AT bus giving 8 MB/s transfer. Current maximum 133 MB/s. based on coupling the interface controller to the PCI bus. DMA - on later systems, DMA bus mastering was provided on the ATA-IDE interface rather than by the standard DMA controller of the system. Data transferred every clock cycle on both rising and falling clock of PCI bus 33MHz * 2 bytes * 2 per clock gives 133 MB/s. DMA required for full speed. Data delivered to interface controller via 32 bit data bus. Timing controlled by a set of registers in interface controller. 33 MHz, 66 MHz, 100 MHz, 133 MHz Depending on how fast the system bus is and how successful data transfers are. If controller senses data lost, it will slow transfer to the next transfer rate. 16 data lines - used to transfer both data, command, and status information between controller and device. Addressing sectors of device, whether LBA or CHS, also occurs across data lines. 3 address lines - allows for different physical devices. The ide/ata interface is capable of accessing 4 channels of 2 devices each. I/O read I/O write ALE - address latch enable Reset Grounds Key or VCC_in - orient the physical position of plug. VCC_in used by some small devices as a power source. PATA does not deliver power via cable, so if plugged in backwards, damage unlikely - just won't work. DDRQ - data direction request. IOCHRDY - i/o channel ready. Cable select - used instead of jumpers to specify which device slave. DDACK - data direction acknowledge. IRQ - interrupt request. Signals need for attention. Combined with other signals to determine which device. GPIO_DMA66_Detect Chip select 1p Chip select 3p Acivity - on powerup, used to detect 2nd device. Then used by drives when they were active on the cable. The protocol describe the interface between the interface controller and the devices as a interface channel. Protocol provides for 4 channels, may implemented on one or more interface controllers. Traditionly requiring IRQ 14,15,11,10 and 4 memory mapped address ranges. Newer pci based controllers multiplex irqs and negotiate memory @. Each channel can access two devices. In general, only the 1st 2 channels are implemented whether a single interface controller chip used or 2 interface cards. Current controllers are capable of talking to each device at its own speed with out affecting interacting with the other. Caveat : since channel can only do one task at a time, controller still has to wait for slower device to complete task issued. So, copying from cd to hard drive faster if on separate channels. In general : keep hard drives on one channel and DVD/CDROMs on separate channel. Ideally - each channel having 1 device provides best i/o speed. SATA SCSI