Ter toevoeging van het vorige antwoord.
Je hebt een type IDE flatcabel waarbij pin 28 tot de master gebruikt wordt, en daarna onderbroken wordt, speciaal voor cable select:
Configuration Using Cable Select
An alternative to the standard master/slave jumpering system used in the vast majority of PCs is the use of the cable select system. As the name implies, with this system the cable--or more correctly, which connector on the cable a device is attached to--determines which device is master and which is slave. The goal of cable select is to eliminate having to set master and slave jumpers, allowing simpler configuration.
To use cable select, both devices on the channel are set to the "cable select" (CS) setting, usually by a special jumper. Then, a special cable is used. This cable is very similar in most respects to the regular IDE/ATA cable, except for the CSEL signal. CSEL is carried on wire #28 of the standard IDE/ATA cable, and is grounded at the host's connector (the one that attaches to the motherboard or controller). On a cable select cable, one of the connectors (the "master connector") has pin #28 connected through to the cable, but the other (the "slave connector") has an open circuit on that pin (no connection). When both drives on the channel are set cable select, here's what happens:
Master: The device that is attached to the "master connector" sees the CSEL signal as grounded, because its connector has pin #28 attached to the cable, and the host's connector has that signal grounded. Seeing the "zero value" (grounded), the device sets itself to operate as master (device 0).
Slave: The drive that is attached to the "slave connector" does not see the CSEL signal as grounded, because its connector is not attached to the CSEL signal on the cable. Seeing this "no connection", the device configures itself as a slave (device 1).
If you switch the devices between the two connectors, they swap configuration, the master becoming the slave and vice-versa. Not a very complicated arrangement, and a good idea, it would seem. In fact, if cable select had actually caught on, it would have been great. The problem is that it has never been widely used, and this lack of universality has made cable select unattractive, which is a bit of a chicken and egg situation. Since cable select was never accepted in the industry, most drives come, by default, with the drive jumpered as a master or single drive. This means that to enable cable select, you have to change a jumper anyway, which obviously negates some of the advantage.
Het is ongelooflijk, maar dit goede idee is ten onder gegaan door de kosten: Men vond het te duur om een gaatje in een kabel te knippen na de master.
