Enabling DMA

[Ken Berry]

This post is not particularly relevant to Video Studio, but may be of interest -- and frankly I am not sure where else to post it!

I regularly burn DVDs produced in VS 8, using a Pioneer DVR-108 dual layer burner in P4 3.0 Ghz CPU 2 GB RAM machine running XP Pro SP2. Burner has worked like a charm from the first moment -- until this morning. I was making copies of a travel flick I made myself, for friends and family. Given that I intended to make copies, I made a Video_TS of the video on my hard disk. I then use Nero Burning ROM to burn them as I can use Nero's 'verify' command to ensure the burned disc matched the original file in all particulars.

First couple of DVDs went through at 4 x burn speed (discs I use are rated at 4x). But after that, I had three that burned at about half speed or less, and the verify process, which normally takes about 6 minutes a DVD, was taking about 25 minutes! The final DVDs nevertheless seemed to be fine and all play on both my computer and stand-alone DVD player.

I thought the problem might be my Pioneer burner, though I have had it for only 3 months (a Pioneer 106 single layer before that). So I tested a disc in it using Nero's DVD-Speed testing tool, which tests among other things the viability and speed of burners. Sure enough, even though set to play at maximum, the disc would only play at half speed. I put the same disc in another computer which has an LG 16x dual layer burner, and tested it with DVD-Speed, and it ran happily at full 4x speed.

Using Nero's Info tool, I then compared the information concerning the optical drives on both computers. On my original one, I noted that the two other optical drives (DVD-ROM and DVD-ROM/CD burner combo) showed as having DMA 'On', while the Pioneer had DMA "Off". On the other computer, DMA was "On" for the LG burner. So I suspected that was the problem. But in reality, I had had no idea that DMA could even be enabled (or disabled) for optical drives, so I have no idea how DMA got turned off. I know how to turn it on or off for hard drives, but had no idea what to do for the DVD burner. So I did a system restore to a couple of days ago, and the Pioneer now shows DMA as "On" and the burning is back up to full speed.

As I say, not particularly relevant to Video Studio, but someone else out there with a similar problem might want to think about this.

And if anyone can tell me how to actually enable or disable DMA on an optical drive, please let me know!

[THoff]

Yeah, you don't need to go back to a previous restore point. The DMA setting is applied to the controller, not the drive. Go to Control Panel -> System -> Hardware -> Device Manager, and expand the IDE ATA / ATAPI category -- this is where the available IDE controller(s) and channels are located. Right-click on the desired channel, go to Properties, then Advanced Settings, and select "DMA if available".

Windows 2000 and XP will under some circumstances disable DMA. In particular, having two optical drives on the same channel can cause conflicts, even if one is configured as master and the other as slave. Optical drives prefer to be masters, or at least not have another optical drive on the same channel, so you may want to rearrange the cables and put one hard drive and one optical drive on one channel.

My motherboard has a standard two-channel IDE controller, each of which can support two devices. In addition, it has a RAID controller that can be configured as a standard IDE controller. I have two hard drives on the RAID controller on their own channel, each configured as master, and two optical drives on the standard IDE controller, again each on a separate channel/cable and configured as master.

[Ken Berry]

Thanks for that Torsten. I knew about the IDE controller(s) (Primary and Secondary), and I could also see on Nero Info, that the same driver controlled DMA on both hard disk and the optical drives. But I could not see within the advanced settings of Device Manager/IDE controller anything to do with optical drives. I should also note that the Pioneer DVD burner in this case is set as a slave. I will do as you suggest and try to set is as a master.

But I confess I still have difficulty understanding how the Pioneer's performance fell away and/or DMA on the controller no longer applied to it without any conscious intervention by this all too fallible human!

[THoff]

PIO (Programmed I/O) is significantly slower than DMA, which is why performance dropped so much. In essence, PIO transfers one data unit (usually a byte, two bytes, or four bytes) at a time depending on the PIO mode, and this requires help from the CPU. In DMA mode, large blocks of data (many kilobytes) can be moved without any help from the CPU.

I have a Plextor PX-716A that runs in UDMA 4 mode if that is supported by the controller, something that even many hard disks don't support.

[Ken Berry]

No, I understand the difference between DMA and PIO. My hard disks support UDMA 5, while the optical drives support UDMA 2. It was just that I had never associated DMA if any form with optical drives, let alone being able to enable or disable this feature for them. I must further confess, in a very red faced way , that I had never really thought about what 'Primary' and 'Secondary' meant in relation to the IDE ATA/ATAPI controller item in Hardware Device Manager... duh! But my eyes are now opened and I thank you enormously.

The mystery remains, though, how the DMA on this particular burner got turned off. Since I did not even know it had this feature, it was certainly not me, or at least not through any conscious action on my part. And I cannot recall anything else strange happening to the computer between one disk, which burned at full speed, and the next, which didn't. I was not using the computer for any other purpose as I have two other computers which I can use for other work. At the same time, I am assuming that DMA must at one time have been enabled for the burner, given that it had consistently worked previously at full speed.