What do IDE channel numbers in BIOS refer to?

Question

On my computer I see the following drives in BIOS:

• IDE channel 0 Master (none)
• IDE channel 0 Slave (none)
• IDE channel 2 Master (my HDD)
• IDE channel 2 Slave (my DVD drive)

What is the meaning of these numbers?

Solution

Each IDE channel is a independent data channel hooked into the south bridge. With IDE, this supports two disks (master and slave) which share the bandwidth on that channel.

Physically each 'channel' connects to a single ribbon cable, which connects to those two drives, with their 'role' set explicitly by jumper setting to master and slave, or automatically by setting those jumpers to cable select.

Practically this means that your HDD and DVD drive are sharing bandwidth, and are on the same channel, and you might want to move it.

I'd note IDE is currently referred to as PATA, and is considered obsolete. Modern drives are sata and have a drive per channel.

Comments

[user]

Are you sure that really is channel 0 and 2? Normally I'd expect it to be 0 and 1, or 1 and 2.

[Thalys]

I'd guess its a mini ATX board and they disabled one of the channels. I 'd plug in one of my older boxes to check, but its too much work for a minor detail ;p