1. Created by Seagate in 1980.
2. MFM encoding with serial transfer.
3. Must set a Drive Select number.
4. Required terminating resistors at both ends.
5. 34 line control cable and 20 pin data cable.

1. MFM: 17 sec/track 512 bytes/sec.
2. RLL: 25 or 26 sec/track
3. 7.5 Mbps transfer rate.
4. Required a low level format.

Start Debug.
At the " - " prompt type:
g=c800:5 "Enter"

1. 24Mbps transfer rate.
2. Some were compatible with ST-506.
3. 34 line control cable and 20 pin data cable.

St-506 / ESDI cable pinout

St-506 / ESDI disk connections

e.g.
If both drives are set to DS 1,
Then the drive at the end of the twisted cable is your C: drive.
St-506 / ESDI Control Cable crossover pinout

Controller   25 26 27 28 29

Drive 1   29 28 27 26 25

Drive 2   25 26 27 28 29

systemboard architecture for IDE drives The ATA standard integrated the disk controller on the hard drive itself; the read/write head control was directed by the hard drive. This proved to be more reliable than sending control signals by a long internal cable as in ST-506 and ESDI drives. Drive performance was also increased because the integration lead to increased clock rates and storage densities. Because of the reduction in components and cables, ATA drives were less expensive to manufacture.
 
ATA-1 Supported transfer modes

Single Word DMA Mode	Multi Word DMA Mode	PIO Mode	Ultra DMA Mode
0, 1, 2	0	0, 1, 2	--

NOTE: ATA-1 is the name of the standard that defines the interface (often the number one designation is dropped and ATA-1 is simply called ATA). Manufacturers and marketeers often refer to the ATA interface as IDE (Integrated Drive Electronics). In practice the terms IDE, ATA and ATA-1 mean the same thing and are interchangable.

systemboard architecture for EIDE drives
 
ATA-2 Supported transfer modes

Single Word DMA Mode	Multi Word DMA Mode	PIO Mode	Ultra DMA Mode
0, 1, 2	0, 1, 2	0, 1, 2, 3, 4	--

NOTE: As with the previous standard, ATA-2 is the official name that defines the interface. The industry often refers to it as EIDE (Enhanced Integrated Drive Electronics). The two terms, ATA-2 and EIDE are interchangable.

The ATA-3 Standard was a marginal enhancement to the ATA-2 Standard. Transfer Modes remained the same. The main features to the ATA-3 standard were S.M.A.R.T and password protection of the hard drive.
 
ATA-3 Supported transfer modes

Single Word DMA Mode	Multi Word DMA Mode	PIO Mode	Ultra DMA Mode
0, 1, 2	0, 1, 2	0, 1, 2, 3, 4	--

Early tape drives and CD ROM's connected through the floppy drive, SCSI or a proprietary interface, since the IDE/ATA interface was designed specifically for hard drives. In an effort to simplify and standardize configurations, the ATAPI standard was created to allow non hard drive components to connect to the IDE/ATA interface. ATAPI devices use regular PIO and DMA transfer modes but require device drivers to be recognized by the operating system.
 
ATA-3 Supported transfer modes

Single Word DMA Mode	Multi Word DMA Mode	PIO Mode	Ultra DMA Mode
0, 1, 2	0, 1, 2	0, 1, 2, 3, 4	--

Defined:

40-pin 80-wire ribbon cable.
cyclical redundancy checking (CRC) for data transfers.

 
ATA/ATAPI-4 Supported transfer modes

Single Word DMA Mode	Multi Word DMA Mode	PIO Mode	Ultra DMA Mode
0, 1, 2	0, 1, 2	0, 1, 2, 3, 4	0, 1, 2

 
ATA/ATAPI-4 Supported transfer modes

Single Word DMA Mode	Multi Word DMA Mode	PIO Mode	Ultra DMA Mode
0, 1, 2	0, 1, 2	0, 1, 2, 3, 4	0, 1, 2, 3, 4

ATA/ATAPI-6 Supported transfer modes

Single Word DMA Mode	Multi Word DMA Mode	PIO Mode	Ultra DMA Mode
0, 1, 2	0, 1, 2	0, 1, 2, 3, 4	0, 1, 2, 3, 4, 5

ATA/ATAPI-7 Supported transfer modes

Single Word DMA Mode	Multi Word DMA Mode	PIO Mode	Ultra DMA Mode
0, 1, 2	0, 1, 2	0, 1, 2, 3, 4	0, 1, 2, 3, 4, 5, 6

At this time (2004) there seems to be some confusion surrounding the Serial ATA standard. First it's not really a standard on it's own, but rather a subset of the ATA/ATAPI-7 standard.
 
The problems with SATA begins with the confusion surrounding it's development. It appears that three different organizations are independently spearheading the development of SATA. There is also some question as to the integrity of data, since the SATA specifications call for unshielded cables that are susceptible to interference.
 
Although higher throughput is projected the current marginal performance boost over Ultra DMA mode 6 may not be cost effective considering the additional hardware costs for running SATA drives as well as the data integrity issues.
 
Prerequisites:

1. Compatible power supply
2. Compatible Motherboard
3. Special SATA data cables

SATA Specifications:

1. 7-pin cable ( 2 data channels)
2. Hot swappable
3. Bandwidth: 150MB/s (2004), 300MB/s (2005), 600 MB/s (2008)
4. Power consumption 250 mV

SATA Issues:

1. Unshielded cables
2. Bottleneck at PCI bus (133MB/s)
3. Development