5 Installation

• A single device on a cable, either a harddisk (ATA) or CD-ROM (ATAPI), should according to the specs never be configured as slave. However, as any ATAPI CD-ROMs come preconfigured as slave, most software works with a masterless slave CD-ROM simply because it saves tech support calls. Moreover some BIOSes have trouble with an ATAPI device jumpered as master. Formally it isn't a valid configuration though; remember this if you have trouble getting the CD-ROM recognized.
• Two harddrives on one channel should be configured as master and slave, respectively. It usually doesn't matter which is which, but older harddisks may not work in all configurations if they predate the standardization of the master/slave protocol. In that case a degree of experimentation will be necessary. Some Conner drives have an ATA/ISA jumper: ATA is the now-standard protocol, ISA is used by older Conners.
• Two ATAPI devices such as CD-ROMs and tapes should work fine as long as one device is master and the other slave, just like harddrives.
• If you need to put a harddisk and an ATAPI device on the same cable, the spec says the harddisk must be the master. Although the reverse will usually work as well in practice, still you'd better avoid the configuration.

Not much. If you have only one drive on the cable, it is best to put it at the very end, especially when you're using any of the faster modes. For two devices, it doesn't matter where you put the master and the slave, or which end of the cable you plug into the controller. Just take care that you plug them in the right way: the red wire is supposed to correspond to pin 1.

When Plug'n'Play ATA arrives the Cable Select (CS) setting will be used, and all of this will change. Some name brand machines may already employ a similar setup.

This is not necessarily the case. Still, it is generally preferable to connect older drives and CD-ROMs to the secondary channel.

If this is not feasible, or if you're wondering if you should upgrade, a few points.

• The speed loss usually referred to is in the interface timing, i.e. the speed at which the devices communicate with the computer. This does not necessarily translate into a real world performance penalty.
• This is mostly an issue with older ATA-2 (EIDE) interfaces and some VL IDE ones. If you have an ordinary ISA IDE interface, it can't get any slower.
• All modern interfaces support distinct timing for master and slave. With these, the slow device does not directly affect the fast one.
• Many CD-ROMs support at least PIO mode 3. This is enough to operate most harddisks on the market today near their maximum speed.

Less than 18 inches. In some cases, the limit is no more than 7 inches.

The cable is a pretty weak link in the whole ATA-2 interface. For the fast transfer speeds used in 'EIDE' systems, there aren't enough ground signals; the cable is unterminated and unshielded. Noise is a real problem. All of this applies to ATA-2 (EIDE) systems more than Ultra-ATA systems, since the latter use checksums to ensure data integrity.

For those reasons, you should take the 18" limit specified by the ATA(-2) standard pretty seriously if you want to avoid data corruption and system hangs. Even worse, some dual-channel 'EIDE' interfaces such as CMD640x based ones have a peculiar design employing only a single buffer for both cables. Most signals on the two cables are directly connected with each other: this means that electrically, the cable lengths add up. Take into account that the copper traces on the circuit board are often a couple of inches long as well and you're facing a maximum cable length of roughly 7" per cable if you want to remain within spec.

If you have difficulties fitting everything in with a standard length cable, consider adding a new plug to it or rolling a complete cable yourself. It's not hard to do, or to track down a friend willing to do it, and you can buy the parts in all electronic parts stores. Do use quality parts, work carefully, and watch that length.

Disregard the above at your own peril. Noise induced problems usually pop up sporadically, can be very hard to detect and even harder to track down. Not least because they may appear completely unrelated and involve devices other than the harddisk.