IDE Channels

Does it matter if i have 2 HD's on the Primary IDE channel?
If i moved the slave HD to the secondary channel would i see a performance increase for the Master HD? Will moving the slave HD to secondary channel decrease the CD-rom Drive speed?

It all depends on your Harddrives and MB. Most new MB can run drives at different speeds on the same channel, but you are sharing the bandwidth between the HDs. You may see a performance boost if you transfer between HDs alot. For mine I run my main HD (boot drive) as a single drive on channel 1, and my secondary (backup drive) as master on channel 2 and my CD-RW as slave on channel 2. As far as you CD-ROM goes, your HD is much faster (unless it is really old) than your CD-ROM, if anything your CD-ROM will slow your HD down.

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Ideally, you want a channel (seperate cable) per drive for the best performance
you do NOT want a CDRW drive on the same channel as your data source as on-the-fly copying is not as good and generally the channel will only be as fast as the slowest unit on it, its only really with SATA drives & channels that this rule may change...

Hmmm, wonder if I can get a valid page fault ???
these invalid ones are far too commonplace...

Most of the information in the previous posts is right ... but out-of-date. What was once fact has become a fallacy, although there are a great many users who are still unaware of this.

The majority of chipsets released since early in 1997 have supported Independent Device Timing, which allows devices to run at different speeds and transfer modes while sharing a cable, without the slowest device on the cable knocking down the "mode" to the transfer rate of the slowest device.

The caveat in this instance is that DMA-capable devices should not be run with PIO-Mode-Only devices, as this will knock both devices down to PIO-Mode. You shouldn't mix these two kinds of devices if you want to use DMA.

The comment that marneus made:

... this is incorrect. (No offense intended, marneus!) Independent Device Timing works quite well with both Atapi and IDE devices, and has been since the 430 chipsets from Intel were released.

It's a little known fact that it is actually best for IDE and Atapi devices <i>not</i> to share the same channel. Atapi is a special protocol that was developed to allow devices like CD-ROM drives and tape drives to attach to regular IDE controllers normally used for hard disks. The newer Atapi protocols that were developed normally make this issue of little consequence, really, but Atapi uses a much more complex command structure, and some Atapi devices cannot deal with DMA bus mastering drivers on older computers (with older operating systems), and will cause a problem if you try to enable bus mastering for a hard disk on a channel they are using.

Of course, if possible, it is best for devices to have an independent channel, and it also true that when transferring information from device to device, you'll get better read/write performance with a configuration like this. By its very nature, each IDE/ATA channel can only deal with one request, to one device, at a time. You cannot even begin a second request, even to a different drive, until the first request is completed. This means that if you put two devices on the same channel, they must share it. In practical terms, this means that any time one device is in use, the other must remain silent. In contrast, two disks on two different IDE/ATA channels can process requests simultaneously on most motherboards. The bottom line is that the best way to configure multiple devices is to make each of them a single drive on its own channel, if this is possible. (This restriction is one major disadvantage of IDE compared to SCSI). An add-in controller is a fairly cheap way of adding extra IDE/ATA channels to a modern PC.

Personally, I think that unless you are doing a great deal of "on the fly" CD burning, the best arrangement is for the hard drives to share the primary IDE cable, and the optical devices to share the secondary channel. Most good burning programs like Nero support burning an image or caching the data to the hard drive before initiating the burning process, which is actually a better solution, IMHO, as the transfer rate from the hard drive to the optical device is faster than from optical drive to optical drive, and there is a lower risk of data corruption due to controller timeouts or errors.

And yes, you will see a performance increase when transferring data between hard drives if they each have an independent channel, but the difference in speed (especially with a fast system and drives with a large cache) is somewhat negligible, in my opinion. Data transfers between two drives on the same cable is usually plenty fast enough for the majority of users, even with the IDE restrictions.

Finally, you may discover that there are some optical devices that won't function correctly unless jumpered as a master on the secondary channel, and this is also often applicable when updating the firmware for a device like this ... many times, the device must be jumpered as master, and temporarily be the only device on the secondary channel, or the firmware upgrade will fail (or even damage any additional devices that are still on the cable.)

That's my take on the situation.

Toey

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I said 'may'... *lol*

no worries, I dont worry about being corrected (havent got much on SATA stuff yet) I was 'dredging' up what I remembered whilst I am at work with no references... mind if I take a copy for my files ???

I would also say that HDDs on primary & optical drives secondary...
if you have a raid & the cable space you could go to town & have a drive on each channel... I did until I added a network card, it & my raid card kept fighting...


Hmmm, wonder if I can get a valid page fault ???
these invalid ones are far too commonplace...