Chester Tan’s article in yesterday’s newsletter made me jump. Actually, I jumped up and started screaming (virtually) “Yes, BUT!”.

The entire IDE/ATA interface is a lot more complicated than the uninitiated appreciate. Oh, it’s easy as pie from a user’s viewpoint- just plug in a drive and go. The details that they don’t even ‘have to’ think about can make a huge difference. I say ‘have to’, because the details they DON’T think about can make that difference.

First off, Chester obviously has a hardware issue going on in his system and while he did a work-around, he didn’t take care of the root problem, that being the drive that Windows wouldn’t recognize. You have to realize that normally, there is nothing to keep you from plugging in two optical drives on one controller. I’ve operated with that setup for years, through several systems and OS’es. Frankly, I suspect that either the drive is jumpered incorrectly or it’s defective/incompatible with his BIOS. It happens more often than manufacturers would like to admit, even in these (supposedly) Plug-N-Play days. Replacing the drive cable let him run the two drives on one channel, but he doesn’t say whether or not it made his original drive show up in Windows.

We all know that the actual IDE controller is built onto every drive and the thing you’re plugging into is just the channel interface. This can lead to potholes in inter-drive cooperation.

Now we come to another issue: SHOULD he want to plug them both into the same controller? The answer is a ‘maybe’ at best. What most people either don’t know or forget about is that the IDE interface can’t issue a consecutive read and then write to the same channel. IDE channel controllers in use today are nummbered zero and one. It can’t read from channel one, drive zero to channel one, drive one consecutively. So, if you have a hard drive on channel zero, drive zero, then the best place to plug in an optical drive is on channel one, drive zero or one. But, if you have a hard drive on channel one, drive zero and that optical drive on channel one, drive zero, then the second optical drive would go to channel zero, drive one. That lets you read from the hard drive and write to the first optical drive at top speed and get good speed when reading from the second optical drive and writing to the first (or the other way round).

See what I mean about details? Yes, the access mode makes a difference, but it’s not the end of the story. I won’t even get into setting DMA…