Running under XP-SP2, when we use a single disk, DMA is active and everything is fine.

When we connect a second physical disk as slave on the same Main IDE Channel, both switch to PIO.

We bought a new 80-connector ribbon and tried several different slave disks. No change.

FYI, both dvd readers are on secondary channel.

Have you set the jumpers on the two drives as master and slave...

As wombat sugested...change the harddrive jumpers to master and slave.

It is fine for them to be on the same ribbon but would actually perform better if the harddrives were on seperate EIDE controllers.

The best scenario for your computer would be to set up the drives as

EIDE 0 (primary) "C" drive harddrive as master and a DVD player as slave on the same cable (perferably 80 conducter cable)

Eide 1 (secondary) 'D" harddrive as master and the other DVD as slave on the same cable. (again preferably 80 conductor cable)

Yes, both are jumpered correctly and recognized by the BIOS.

Original setup described worked quite well for the past 2 years. Things went wrong when we discovered wire connector was defective and we bought a new one.

Will change arrangement and report back.

The issue was solved a bit by chance. We went into the BIOS to see whether DMA could not be forced from there. As it turned out, we could not since we were faced with a Department Store Tower, nevertheless with a Gigabyte MB and AMI BIOS, 5 or 6 years old (Pentium 4, 1.7 Ghz).

It's at that point, in the BIOS, that we noticed that the two disks were set to User-defined. When we changed this to Auto, the problem was solved and everything was back to normal as it was before we ran into the defective connector issue which started all.

BTW, is there really that much of an improvement in throughput when you mix dvd reader and disk? Is it simply because you have the 2 disks on different controllers?

Thnaks to all for the suggestions which put us on the right track.

On one of my computers I have two Samsung hard drives on the same 80 connector ide cable, set as Master and Slave, and two Samsung dvd burners set as Master and Slave on it's own separate 80 connector ide cable.

I have not noticed any ill effects by doing this sort of setup in the last three years I have been doing this...

__________________


Wombat's: Bulldozers of the bush...

No, there won't be any ill effects...and it would depend on what a person was doing whether or not there would be any truely noticeable differences either. Also it is dependent on whether one is using 32 bit or 64 bit technology as Mr. Wombat does. Which is why you don't see any ill effects . without getting too technical 64 bit works the IDE controller differently than 32 bit technology!

Yes........
The IDE controllers have 2 channels...channel 0 and channel 1....and you can attach either optical drives or harddrives to either channel and in any configuration and believe it or not either channel can be designated master or slave without any ill effects (not true with older computers configurations)

With only two channels and 1 controller....the issue is that data transfer can only be made on one channel at a time. so if data is being used on channel 0 then channel 1 is mute till the data transfer on channel 0 is complete then channel 0 becomes mute and data is transfered on channel 1.

If two harddrives are connected to one IDE controller then data transmitions are intermitted especially when transfering data between each other. Now if the two harddrives are set up on different IDE controllers they can basically communicate between each other at almost twice the speed of the other set up because they can communicate simultaneously.

This becomes true for optical drives as well....
if you have a CDrom and a CDrw on the same IDE controller and you use them to copy discs then the copying takes a longer amount of time (disc to disc) because the disc must wait on each other . If set on different IDE controllers then they communicate at the same time.

On faster computers one may not see much difference but on slower computers there will be a remarkable difference.

This is actually what led to the developement of SATA controllers. All SATA basically is, is an IDE controller with a single channel forcing each device to transfer data faster.

Hope that clears it up a bit!

Thank you for the explanation