Here is some information that you can check in a couple of minutes on
your own PC. 

Hopefully it will be useful to some, with apologies to those who
already know this like the back of their hand. I have searched the
forum and the wiki to see if there is already a comprehensive write-up
about this, but didn’t find one.

I have placed the thread in this forum, as the problem will often be
provoked by the action of securely ripping a disc, especially if that
disc has errors.

This information is for Windows XP users, although I believe it also
applies to Vista. For Mac and Linux, perhaps someone else could
comment. It applies to the IDE devices that most of use, but I am not
sure if it is true for PATA and SATA.

In this post I will describe the problem, and the fixes (of which there
are two levels), and provide some links to articles with screenshots.

Transfer Mode:
There are two basic transfers modes for IDE devices, DMA and PIO mode.
DMA mode (Direct Memory Access) is much faster than PIO mode
(Programmed Input Output). PIO mode also uses the CPU to control the
access, and thus a device that is operating in this mode can pull a
significant CPU percentage to operate. DMA mode has a number of levels
(speeds) depending on the speed of the device. Typically a HDD will
operate at DMA Mode Level 5, whereas a CD-RW may only operate at DMA
Mode Level 2.

Modern HDDs, DVD drives, and CD-RW drives can all use DMA mode, whereas
most older CD-ROM drives cannot. When initially installed, windows will
set the best mode for the drive.

The Problem:
Windows “protects” the user from bad drives corrupting data by
monitoring the amount of CRC and timeout errors and if it encounters
more than six such errors it downgrades the mode. Eventually it will
downgrade the drive to PIO mode. See the “for repeated DMA errors”
section here:

http://www.microsoft.com/whdc/device/storage/ide-dma.mspx

My experience is that this action can easily be provoked by secure
ripping a CD that has some difficult to read sectors. Additionally, if
the optical drive you are using shares an IDE channel with your system
HDD, it may also downgrade the transfer mode of the HDD as well.

If only the optical drive is affected, then you will find that rips
will be slower, and the performance of the entire machine will be
adversely affected when the drive is being used. If, however, the HDD
is affected, then your PC will suddenly start acting like a slug.
Performance will be totally destroyed, and you will have major problems
running applications at any speed. I would very likely cause dropout
problems with SS or SC7 due to the overloading of the CPU. I have
experienced this.

Checking:
Fortunately checking is easy and quick. First you need to open Device
Manager, which you can do by clicking ‘Start’, then right click ‘My
Computer’, select ‘Properties’, click the ‘Hardware’ tab, and then the
‘Device Manager’ button.

Once the device manager has opened, click on the plus next to the entry
for IDE ATA/ATAPI Controllers. There you will see entries for the
primary and secondary IDE channels. For each channel in turn, right
click on the entry, and select ‘Properties’. Click the ‘Advanced
Settings’ tab and you will be able to see the modes for each of the two
possible devices on the channel.

If when you do this the ‘Current Transfer Mode’ for all devices is set
to DMA mode, then you have no problem, and can go away happy. If one or
more of the devices is set to ‘PIO mode’, then you should fix this.

First Fix:
There is an initial process to try and reset the mode. Unfortunately
this will often not work, but it should be attempted. What you need to
do is to ‘toggle’ the mode to convince windows to reset the device.
This is done as follows:

>From the dialogue you used to check the current mode, select “PIO only”
as the transfer mode from the drop down menu. OK out of the dialogue,
and then reboot.

Once you have rebooted, return to this dialogue and select ‘DMA where
available’ as the transfer mode from the drop down menu. Once again OK
out of the dialogue, and reboot. 

Return again to this dialogue, and check to see if the current transfer
mode has now been set to “DMA mode”. If you are very lucky this will
have worked, and you need not do anything else.

Second Fix:
Very often Windows refuses to play ball with the first fix. This was
supposed to have been dealt with in XP SP2, but in my experience this
is untrue. If you cannot get out of PIO mode using the first fix, then
you have two options: either uninstall the IDE channel, or edit the
registry.

I prefer not to edit the registry, but details of how to do this are
included in some of the links I have included below. Personally I use
the uninstall option.

To uninstall the channel, right click its entry in the Device Manager,
and click uninstall. At this point windows will warn you about what you
are about to do, click yes to continue, and then reboot the machine.
When the machine reboots it should automatically find you uninstalled
channel, and reinstall it.

WARNING: it has been written that if you uninstall the channel
containing the HDD with windows on it, that you may have a problem
reinstalling. I have done this with no problems on a couple of my
machines, but I cannot guarantee this for other people’s machines. This
normally applies to the primary channel. If you are nervous about this,
then use the registry edit described in the links.

Useful Links, some with screenshots:

http://www.techmind.org/dvd/index.html
http://www.cdrlabs.com/forum/viewtopic.php?t=7625
http://audacityteam.org/wiki/index.php?title=DMA_mode

or try googling ‘dma pio mode xp’


-- 
bigfool1956

David Ayers
Music is what counts, hifi just helps us enjoy it more
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