Timothy Daniels said:
My 2 hard disks certainly support bus mastering - they're both
Ultra ATA 133 and the same model made by the same manu-
facturer. The Dell chipset and BIOS support bus mastering in
support of ATA 33. And the Promise and SIIG Ultra ATA 133
expansion cards support bus mastering. The OS is WinXP Pro.
It sounds like everything is a go for bus mastering for both the 2
hard drives (attached to the expansion card) and the optical devices
hooked to the legacy ATA 33 bus. It may be insignificant in effect,
but bus mastering caught my attention because I felt it might
compensate for putting both hard drives on the same IDE channel
rather than give each its own dedicated IDE channel in the interest
of fast hard drive-to-hard drive volume imaging. What do you think?
If 2 HDs on the same channel could transfer data directly from one
to the other via bus mastering, might it be faster than HDs on 2
channels
that have to transfer data to and from a RAM buffer on the expansion
card or in main memory in order to transfer data from one to the other?
In other words, given 2 modern HDs in a bus mastering enabled
environment, would HD-to-HD data transfers go faster if they're put
on different channels or on the same channel?
*TimDaniels*
As I've thought about it, and refreshed my memory I don't really think that
bus mastering will increase the speed of transfer between your drives ...
not as long as they are connected to the same port anyway.
Bus mastering allows a device to take over or "master" the bus (the PCI bus,
that is) if it needs it. This can make things operate more smoothly in a
multi-tasking environment. But you have to remember that you are still
dealing with only one IDE controller port.
Yes, the controller itself can "master" the bus, and because of UATA it can
also do DMA (Direct Memory Access) which means that the drive can dump data
to the memory without troubling the processor, which can also increase
performance.
None of this, however, allows the drives to talk directly to one another and
transfer data completely independently of the rest of the system. They will
still have to use a RAM buffer no matter what.
Using separate ports, however, the controller can simultaneously read from
one drive while writing to the other ... facilitating basically the same
thing as one drive speaking directly to the other. This is why it is
*always* better to have your drives on separate ports. This is the fastest
configuration.
It sounds like you have enough ports to do it this way. Use the two ATA33
ports on the mobo for your optical drives, and give each of your hard drives
a separate port on your PCI controller card. This will work the best ... for
hard drive performance anyway ... your optical drives might possibly benefit
from the increased speed of the add-in card, but probably not.
I also might suggest that you go with round IDE cables ... I run a RAID
array with two 80gig drives, each on their own port (on a RAID expansion
card), as well as a DVD-ROM and CD-RW, each with their own port (on the
mobo). Add in a floppy cable and it gets a little hard for the air to move
around in there because of all the ribbon cables (5 total) obstructing the
air-flow. I lowered both my internal ambient temperature as well as my
processor temperature significantly by switching to round cables.
Drumguy