Two DMA Hard Drives on Primary IDE Channel

Two DMA Hard Drives on Primary IDE Channel

Post by JAWs » Mon, 15 Nov 2004 23:39:25

My Dell 2400 3.0 GHz machine came equipped with one 40 GB hard drive.
When I attempted to capture analog video, I was dropping a third as
many frames as I was capturing, and the software I was using suggested
that I needed to be capturing to a dedicated, 7200 RPM drive. I
bought a 160 GB drive (for $60 after rebate), installed it (per Dell
instructions as a Cable Select device), captured to it, and discovered
that the dropped frame rate was even worse.

The physical layout of the Dell case separates the optical drive bays
from the HDD bays by a distance that is too great to make the HDDs the
masters of their respective channels with the optical drives as
slaves, so I installed the new drive as a slave of the boot drive.
(The optical drive bays are in the top and the HDD bays are in the
bottom of the mid-tower case.) I checked a little further and found
that the slave drives on both channels are running in PIO mode, even
though the Transfer Mode is set to "DMA if Available". Both primary
devices are running UDMA Mode 2.

I tried toggling the Transfer Mode by selecting "PIO Only" for both
slaves, exiting, rebooting (just to make sure it "took"), selecting
the "DMA if Available" Transfer Mode on both slaves, exiting, and
rebooting again. Both slaves remained in PIO mode.

Since I don't plan to capture analog video very often, I would be
willing to disconnect the optical drives from the secondary IDE cable,
then hook up the new HDD as the secondary master whenever I'm
capturing. However I'm concerned about juggling this amount of
cabling, and am a little worried that XP will decide that it is trying
to be run on am unlicensed machine.

I apologize of all the "story" before my questions:

1) Does having both HDDs on the same channel negate the benefits of
having a dedicated drive to capture to?

2) Is there any reason that two HDDs on the same channel cannot both
operate in DMA mode?

3) Is it risky to pull the secondary IDE cable off of the optical
drives and temporarily use the secondary master for my capture drive?

4) Is there anything inferior about using Cable Select?


Jim Williams

Two DMA Hard Drives on Primary IDE Channel

Post by Mike Wals » Tue, 16 Nov 2004 01:08:57

No, an IDE port operating in DMA mode 5 (100 MB/sec) can easily handle 2 drives at the same time.

You should be able to run 2 drives in DMA mode. Most drives 40 GB and larger will run in DMA mode 5.
It is possible that your motherboard IDE port does not support faster than DMA mode 2, and that the 160 GB drive supports only DMA mode 4, 5, and 6 and therefor defaults to PIO mode. If this is the case to need to get a PCI adapter that supports DMA mode 5 and 6.


Cable select often does not work properly, I always use master/slave.


When replying by Email include NewSGrouP (case sensitive) in Subject

Mike Walsh
West Palm Beach, Florida, U.S.A.


Two DMA Hard Drives on Primary IDE Channel

Post by JAWs » Tue, 16 Nov 2004 23:57:47

hanks, Mike. The problem turned out to be that the slaves were
turned off in CMOS. I thought about that earlier, but since I
couldn't seem to access setup, I started looking in other directions.
I finally replaced my wireless keyboard with a wired one, and was able
to access setup with no problems.

Thanks for getting me thinking in the right direction again.


On Sun, 14 Nov 2004 16:08:57 GMT, Mike Walsh < XXXX@XXXXX.COM >