Enhanced Small Disk Interface
Enhanced Small Disk Interface (ESDI) was a mass storage interface developed by Maxtor Corporation in the early 1980s as the successor to the ST506 interface . ESDI relocated some parts of the controller to the drive electronics, such as B. the data separator, and the control bus was generalized so that more additional devices could be controlled (such as removable media and tape drives). ESDI used the same cables as the ST-506 (a 34-pin common control cable and a 20-pin data cable for each drive) and could therefore easily be used to replace an ST-506 application.
ESDI was very common in the mid to late 1980s because SCSI and ATA were still very immature and ST-506 was simply not fast enough. ESDI supported data rates of 10, 15, or 20 megabits per second (whereas the highest possible speed of ST-506 was 7.5 Mbps), many contemporary high-end SCSI drives were actually ESDI drives with a SCSI bridge in the Drive electronics.
After the more flexible SCSI was standardized in 1986 and ATA quickly replaced the ST-506 in the desktop area, ESDI quickly lost its importance and was practically no longer used in the mid-90s.
Terminal assignment
| GROUND | 1 | 2 | ~ HD SLCT 3 |
| GROUND | 3 | 4th | ~ HD SLCT 2 |
| GROUND | 5 | 6th | ~ WRITE GATE |
| GROUND | 7th | 8th | ~ CNFG / STATUS |
| GROUND | 9 | 10 | ~ XFER ACK |
| GROUND | 11 | 12 | ~ ATTENTION |
| GROUND | 13 | 14th | ~ HD SLCT 0 |
| Key (no pin) | 15th | 16 | ~ SECTOR |
| GROUND | 17th | 18th | ~ HD SLCT 1 |
| GROUND | 19th | 20th | ~ INDEX |
| GROUND | 21st | 22nd | ~ READY |
| GROUND | 23 | 24 | ~ XFER REQ |
| GROUND | 25th | 26th | ~ DRV SLCT 0 |
| GROUND | 27 | 28 | ~ DRV SLCT 1 |
| GROUND | 29 | 30th | Reserved |
| GROUND | 31 | 32 | ~ READ GATE |
| GROUND | 33 | 34 | ~ CMD DATA |
| ~ DRV SLCTD | 1 | 2 | ~ SECTOR |
| ~ CMD COMPL | 3 | 4th | ~ ADDR MK EN |
| GROUND | 5 | 6th | GROUND |
| + WRITE CLK | 7th | 8th | - WRITE CLK |
| GROUND | 9 | 10 | + RD / REF CLK |
| -RD / REF CLK | 11 | 12 | GROUND |
| + NRZ WRITE | 13 | 14th | -NRZ WRITE |
| GROUND | 15th | 16 | GROUND |
| + NRZ READ | 17th | 18th | -NRZ READ |
| GROUND | 19th | 20th | ~ INDEX |