IDE Controler CMD 0649 PIO Mode 4 only

[Guest]

I use the IDE Controller CMD 0649 chipset for my DVDRRW optical rives the
controller is capable of ATA 100. Device Manager shows it as PIO mode 4 &
the Enable DMA box is disabled.
Editing the registry manually I am able to change to DMA mode but it resets
upon a reboot.

 

[Cari \(MS-MVP\)]

First thing to check is that you have an 80 wire cable and not an old 40
wire.

 

[Peter M]

PIO 4 is actually multi-word dma 2 which is what many optical drives still
only run at.

 

[Guest]

Firstly I must point out that I have Dual Boot and am running XP Pro on the
same PC for 2 years without any DMA issues
I have six DVDRW drives in the system using 3 IDE controllers all with 80
wire ATA-133cables
4 drives should operate at Ultra DMA Mode 2 & two should operate at Ultra
DMA Mode 4. They operate successfully at these settings when I boot up into
XP Pro.
In PIO mode 4 excessive CPU usage is noticed and the writing speed is
restricted to 4x, this is as expected with PIO mode
Using a Pioneer burner on the M/B IDE channel I can get the correct Ultra
DMA Mode 4, but unfortunately I do not have any spare IDE on my M/B

The issue is with the controller drivers supplied with the OS and not the
hardware set up