"Timothy Daniels" <(E-Mail Removed)> wrote in message news:LdqcnYoh5dHEA6miU-(E-Mail Removed)...
>
> "drumguy1384" wrote:
> >
> > "Timothy Daniels" wrote:
> > >
> > > "Ed Light" reported:
> > > > Looking in device manager, there most certainly is
> > > > a "VIA Bus Master IDE Controller" on my kt400 board.
> > >
> > >
> > > The Dell tech rep reports a "2 bus mastering IDE channels
> > > on the PCI bus ATA spec compliant" as well. I haven't
> > > heard back from Promise or SIIG, though. Their reps
> > > didn't know what bus mastering was, so they had to send
> > > an email to their engineers in Taiwan. :-)
> > >
> > >
> > > *TimDaniels*
> >
> > From the article you posted a link to on IDE Bus Mastering:
> >
> > "Bus Mastering Hard Disk: Normally this means that the drive must
> > be capable of at least multiword DMA mode 2 transfers. All Ultra
> > ATA hard disks also support bus mastering."
> >
> > Also, from that same article:
> >
> > "Bus mastering IDE will not help at all in the following situations:
> >
> > * It will not make that 100 MB transfer from C: to D: that you are
> > sitting and watching go much faster at all.
> > * It will not speed up DOS games.
> > * It will not make applications load more quickly (unless you
> > somehow are loading more than one at a time).
> > * It will not speed up single applications."
> >
> > This article, however, was written when Windows 95 was the premiere
> > OS for the PC (not a true multi-tasking OS) ... it is quite possible that
> > IDE bus mastering has been improved on in the time since then. However,
> > aside from higher speeds, IDE drives have not changed much, nor has
> > the PCI bus.
> >
> > Also, you can rest assured that the Promise and SIIG controllers will
> > do bus mastering. The UATA spec requires it. That's why Dell reported
> > their controllers "ATA spec compliant."
> >
> > In fact, I have a SiS UATA133 RAID controller that would not detect the
> > drives connected to it at all until I enabled "external PCI controller bus
> > mastering" in the BIOS.
> >
> > Hope this can shed some more light.
>
>
> 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?
That you're getting FAR too anal.
Why dont you actually try the two configs, both on the one
ribbon cable and each on a separate ribbon cable and see
if you get any real improvement in the speed of ops where
you are sitting in front of the PC waiting for it to happen ?
If you do crude image backups much, try that too, but bear in
mind that if you have any sense you wont normally sit around
twiddling your thumbs in front of the PC waiting for the image
creation to happen, so even if you can see a small speedup with
the creation of a compressed image, its completely academic.
> If 2 HDs on the same channel could transfer data
> directly from one to the other via bus mastering,
You're getting completely confused here too. The
short story is that as long as you have DMA enabled
and in use, thats all that matters with modern hard
drives and motherboards and IDE controller cards.
> 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?
Nope, the problem is the theoretical simultaneous access to
both drives at once. Since both drives on the same ribbon
cable cant be SIMULTANEOUSLY reading on one and
writing on the other, in theory that config will be slower.
In practice apps like Ghost dont actually attempt to
read on one and write on the other literally simultaneously
anyway. They read from one into memory, then write
from memory onto the other when creating an image file.
With quite a bit of time taken to compress the image file.
> 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?
Separate channels will ALWAYS be theoretically faster just
because you can literally simultaneously read off one and
write on the other drive. BUT in practice very few apps actually
do that in practice, so the difference is very theoretical in practice.
And its a rare app that would even benefit from that possibility
in the real world with modern desktop systems anyway. And
what few there are that could theoretically benefit, arent normally
used with the user sitting in front of the PC twiddling his thumbs
waiting for the op to happen with a modern desktop PC.
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