These cables are diffficult to handle, if you want to make a nice PC. The are so big, that they disturb the air circulation and hence the cooling inside the PC cabinet.
Since each channel can handle two units, there are two of these connectors on the system board. Note the blind hole in top center. Note also the stripe (it is red) in the far right edge of the cable. It tells you that lead number one is on this edge. Both of these features help prevent incorrect installation of the cable.
If we have to use all four connections, it causes some problems. The setup may look like this:
|Primary, master||Hard disk 1|
|Primary, slave||Hard disk 2 or CD-ROM|
|Secondary, master||CD-RW DVD drive|
|Secondary, slave||ZIP/LS120 diskette drive|
Typically, a PC has two EIDE units connected: the hard disk and the CDROM drive. However, as you can see, other units can be connected as well. The hard disk must must be on the primary EIDE channel. On some system boards, this has the greatest transfer capacity.
This is due to the fact, that the two main controllers (primary and secondary) are capable of multitasking. The two channels can process data simultaneously and independently, at the same time.
The two sub-channels (slave and master) do not multitask; here only one operation is processed at the time, be it on the master or on the slave channel.
So for best performance, the two harddisk have to be assigned one at the primary EIDE channel and the other at the secondary EIDE channel. This leaves us with the problem of the CD-ROM drives, which also have to be placed on EIDE channels.
My conclusion is that if you have to use two EIDE harddisks (and many of us do), the motherboard should be enhanced with further EIDE channels. Please continue the reading...
To learn more
Read more the boot process and system bus in Module 2b
Read about file systems in module 6a
Read about I/O buses in module 2c
Read about the motherboard chip set in module 2d
Read about RAM in module 2e
Read Module 5c about SCSI, USB etc.
Copyright (c) 1996-2005 by Michael B. Karbo. www.karbosguide.com.