Dave said:
I,ve read on a PC building site that one shouldn't put an optical drive
(such as CD or DVD) on the same IDE connection because that will force the
Hard drive to run at the slower speed of the Optical drive.
OK, but if there is a CD drive on the same IDE connection with a DVD drive,
will that force the DVD drive to run at the slower speed that the CD drive
runs at ?
If you have an ATA 100 device with an ATA 133 device on the same bus,
the bus will run at ATA 100 transfer rates for both drives.
The speed of the drives, eg whether they are 64x or 1x, matters not -
if they are both ATA 133, the bus will run at ATA 133 transfer rates for
both of them.
You can run a CD/DVD on the same cable as an HDD, if they are both in
DMA mode and both are the same ATA rating, without adversely affecting
the HDD.
The slower reading rate (which is determined by the 1x <> 64 x rating of
the drive) simply means that the CD/DVD grabs the bus for transfers less
often than an equivalent HDD would do. Thus a pair of hard disks is
better split between the two IDE cables - provided anything else on
those cables has the same ATA 100/ ATA 133 rating as the HDD and is
running in DMA mode.
However, if the CD/DVD is not in DMA mode then the processor has to poll
it for data, which will result in additional bus activity which will
impact on the performance of an HDD on the same cable. If the CD/DVD is
not in DMA mode, it should not be put on any cable with a HDD or
anything which can run in DMA mode.
Just about the worst thing you could do is to put an ATA 133 HDD on the
same cable as a non-DMA ATA 33 CDROM.....
