Explanation of DMA:

DMA is an abbreviation for Direct Memory Access, an access method for external devices where the data transfer is not done by the central processor, but by a small special processor called DMA controller. It uses a procedure called cycle stealing, where the central processor memory access cycles are delayed for very short times to intersperse DMA controller memory access cycles. Some newer, faster DMA modes are called UDMA (Ultra DMA).

The alternative, slow and inefficient data transfer mode is called PIO, Programmed Input-Output, where the central processor transfers data byte for byte or word for word. This requires many processor commands for each data word and therefore causes a high and unwanted processor load.

The most common reason why a CD or DVD port falls back to PIO mode is a drive trying over and over to read a scratched or dirty CD or DVD.

For repeated DMA errors. Windows XP will turn off DMA mode for a device after encountering certain errors during data transfer operations. If more that six DMA transfer timeouts occur, Windows will turn off DMA and use only PIO mode on that device.

In this case, the user cannot turn on DMA for this device. The only option for the user who wants to enable DMA mode is to uninstall and reinstall the device.

All CRC and timeout errors are logged in the system event log. These types of errors could be caused by improper mounting or improper cabling (for example, 40-pin instead of 80-pin cable). Or such errors could indicate imminent hardware failure, for example, in a hard drive or chipset.

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IN THIS GUIDE, I CHECK THE PRIMARY IDE CHANNEL FIRST, JUST TO SHOW YOU HOW. YOU MUST CHECK THE SECONDARY IDE CHANNEL FOR THAT IS WHERE YOUR CD/DVD DRIVES ARE. JUST RESETTING THE PRIMARY IDE CHANNEL TO DMA WILL NOT HELP IF YOUR SECONDARY CHANNEL IS IN PIO MODE. AGAIN, MAKE SURE YOU CHECK THE SECONDARY IDE CHANNEL AFTER CHECKING THE PRIMARY IDE CHANNEL.

In this guide I will show you how to check your DMA status and reset it if necessary.

Lets begin by clicking the Start button, then right clicking on "My Computer" (red), then left clicking on "Properties" (blue) or by right clicking on the "My Computer" icon (green) on your "Desktop" then left clicking on "Properties" (yellow). (Screen Shot Below)



or

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After left clicking "Properties", this screen will come up. There should be 7 different tabs at the top (red). For this guide, the only one you are concerned about is the "Hardware" tab (blue). Click on the "Hardware" tab. (Screen Shot Below)

After clicking the "Hardware" tab (red), your screen should look like this. Now go ahead and "Device Manager" (blue). (Screen Shot Below)

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After clicking "Device Manger", it should have opened up this screen (red). Now find "IDE ATA/ATAPI controllers" (blue) in the list. Click the plus sign out to the left of it (+) (green). (Screen Shot Below)

After clicking the plus (+) sign, it should have revealed the "Primary IDE Channel" (red) and "Secondary IDE Channel" (blue). Don't worry about what else is listed there. (Screen Shot Below)

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Generally your hard drives are on your "Primary IDE Channel" and your CD-ROM/DVD-ROM/DVD+RW drives are on the "Secondary IDE Channel". %90 of the time, only your CD-ROM/DVD-ROM/DVD+RW drives will revert back to PIO mode but, its a good idea to go ahead and check both why your already here.

Ok lets check your "Primary IDE Channel" first. So right click on "Primary IDE Channel" (red), then left click on "Properties" (blue). (Screen Shot Below)

After left clicking "Properties", this screen will come up with 5 tabs at the top (red). (Screen Shot Below)

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Go ahead and click the "Advanced Settings" tab (blue). On this screen it will show you what "Transfer Mode" (red) its currently in, you want it to say "DMA if available". ***Just because it says "DMA if available", doesn't mean the drive is in DMA mode!*** It also shows what the "Current Transfer Mode" is (green). The "Current Transfer Mode" is what you are going to look at %99.9 of the time. You never want it to say "PIO Mode"! The higher the mode #, the faster it goes. Ultra DMA Mode 5 is faster than Ultra DMA Mode 4 and so on. Ultra DMA Mode 5 is the fastest mode you can achieve for the hard drives. (Screen Shot Below)

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It also tells you how the drives are configured with the IDE cables. Example, "Device 0" (purple) means that the drive is set at the "Master" position and "Device 1" (yellow) means that the drive is set at the "Slave" position.

If it says "PIO" mode in the "Transfer Mode" box (red), click the down arrow and change it to "DMA if available" (blue). (Screen Shot Below)

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If it says "PIO" mode in the "Current Transfer Mode" box, click the "Driver" tab (green), then click the "Uninstall" button at the bottom (purple). (Screen Shot Below)

After clicking the "Uninstall" button, this warning message will pop up from Windows. Just click the "OK" button (red). ***After you reboot, Windows automatically re-installs it, so don't panic.*** (Screen Shot Below)

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After clicking "OK" on the above message, this windows prompt will come up. You have to click "Yes"! (Screen Shot Below)

Upon rebooting, if you watch near your PC's clock area, some notifications will pop up telling you it has discovered some new hardware. That is normal, as it is just re-detecting your Primary IDE Channel.

It may (mine did) tell you that you have to reboot again for it to be installed properly. Reboot again, and your all set!

Your DMA should look like this below:

Primary IDE Channel (red)

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If the "Secondary IDE Channel" is in PIO mode in either box, do the same steps that you did for the "Primary IDE Channel".

Secondary IDE Channel (blue) - (Most disc drives have a limitation of UDMA 2 Mode, so thats as high as they will go, so don't freak out.)