IBM introuduced the first PC to include BIOS support for hard drives, it supported up to 2 physical drives and each drive could be up to 504 MB, far larger thean the 5-MB and 10-MB drives of the time
Only 2 drives per cable
ATA-1 Standard defined that no more than two drives attach to a single IDE connector on a single ribbon cable.
ATA -AT attachment interface was a new hard drive interfaced introduced in march of 1989
PIO and DMA Modes
ATA-1 defined two methods, the first using programmed I/O (PIO) addressing and the second using direct memory access (DMA) mode.
PIO is nothing more than the traditional I/O addressing scheme, where the CPU talks directly to the hard drive via the BIOS to send and recieve data. Eventually 3 different PIO speeds called PIO modes were adopted.
DMA modes are defined as a method to enable the hard drives to talk to RAM directly, using old-style DMA commands. The old-style DMA was slow and the resulting 3 ATA single-word DMA modes were also slow.
Industry adopted improvements to the ATA standard and called it ATA-2. MAny people called these new features Enhanced IDE. EIDE was really no more than a marketing term invented by Western Digital but it caught on in common vernacular and is still used today, although it is fading out.
Higher Capacity with LBA
Higher Capacity with LBA (logical block addressing) came along. Logical block addressing is when the hard drive lies to the computer about its geometry through an advanced type of sector translation. Geometry!
In 1994 Pheonix Technologies came up with a new set of BIOS commands called Interrupt 13 extensions. They broke the 8.4 GB barrier by completely ignoring the CHS values and insead feeding the LBA a stream of addressable sectors.
ATA-3 came on quickly after ATA-2 and added one new feature called S.M.A.R.T. (self-monitoring analysis and reporting technology
ATA-4 introduced a new DMA mode called Ultra DMA that is now the primary way a hard drive communicates with a PC> Ultra DMA uses DMA bus mastering to achieve far faster speeds than were possible with PIO or old-style DMA.
Ultra DMA was such a huge hit that the ATA people adopted 2 faster Ultra DMA modes with ATA-5.
Hard drive size exploded in the early 21st century. ATA-6 also introduced ULTRA DMA mode 5 kicking the data transfer rate up to 100MBps.
ATA-7 brought 2 new innovations to the ATA world. One evolutionary and the other revolutionary. The evolutionary came with the last of the parallel ATAUltra DMA modes, the revolutionary was a new form of ATA called serial ATA (SATA).
ATA/133 was introduced by ATA-7, the fastest and probably least adopted of all the ATA speeds. Runs up to 133 MBps.
The SATA bridge came along and it was an adapter that allowed PATA devices to be connected to a SATA controller.
WIndows Vista and later operating systems support the Advanced Host Controller Interface or AHCI which is a more efficient way to work with SATA HBAs.
External SATA (eSATA)
The External SATA extends the SATA bus to external devices. The eSATA drives use connectors similiar to internal SATA but they're keyed differently so you can't mistake one for the other.