DMA Modes? Speeds.. and question

Ok I am kinda confused on DMA modes… how fast are DMA modes? how many megs a second?

DMA 2?
DMA 3?
DMA 4?

my question is I have two DVD burners in my other machine they are both in mode 2, for some reason one of the burners keeps buffer underrunning when I burn two DVD’s at the same time, is this because they are in Mode 2?

mode 2 Im guessing is 11 megs a second?

is that why I am having underruns?

do both drives have to be able to get 11 megs a second? (8x speed)

What is the source of the burns? If it’s a single HDD then forget it as it won’t work properly. Likewise if the burners are on the same IDE Channel/cable.

The only way to burn simultaneously with good speed is with the burners on separate channels & burn from 2 HDDs that are also on their own IDE/SATA channels.

Otherwise buffer underruns, wild buffer fluctuations etc will occur.

The burst rate attainable by a burner in mode 2 should be around 23mbs & in mode 4 around 46mbs.

Wikipedia tech article:

The only way to burn simultaneously with good speed is with the burners on separate channels & burn from 2 HDDs that are also on their own IDE/SATA channels.

Or, use a WD Raptor HD which, if not fragmented, will burn 2 separate jobs easily.

Burning 2 discs from the same process (multiple copies of the same compilation), should work fine with both burners on the same channel, at lower speeds, as long as the 2 burners are identical. YMMV

hmmm… I have a WD 160 gig IDE drive in my main machine with two liteon burners (in my main machine the liteons are running in DMA 4) and it burns two DVD’s fine at 8x each, no problem I was just asking what were the speeds and is it BECAUSE the burners in the other machine are runnining in DMA mode 2?

thanks

DVD burners never exceed the speeds available in UDMA-2. The difference between UDMA-2 and 4 is meaningless for optical drives. So the answer to your issue is somewhere else, not in the interface speed. Either they are on the same channel, or the hard drive is too slow, or both.

before I had a HP DVDRW and a Liteon DVDRW thats why… sorry should have specified

I bought another liteon for my machine today, it went to DMA mode 4 just as the other liteon and its working perfect, before one of the drives was in DMA2 and one was in DMA4 so thats what was causing the problem