Yesterday I got a call from a friend with very typical problem. His DVD drive suddenly got a lot slower and refused to burn discs at speeds over 2x.
This is usually caused by string of errors (from trying to read scratched disc for example) that makes Windows to drop drive into low performance mode. Quite easy to fix if you know what to look for.
There are two types of modes in which drives can operate:
- Programmed input/output (PIO) – this is legacy mode that makes heavy use of processor and has very limited transfer rates. No modern device should be used in this mode.
- Direct memory access (DMA) – much faster, in this mode drives can communicate with memory directly, bypassing processor.
As described in this knowledge base article if Windows encounters string of errors it changes mode for that drive to slower and slower, all the way until it drops to PIO. Which results in massive loss of performance and high CPU usage on operation.
First issue must be confirmed as such. Locate in Device Manager (Win+Break) IDE channels and click through them.
Advanced settings tab has details about current mode (Not Applicable means nothing attached to the channel).
If any of drives had dropped to non-DMA mode then that channel must be reinstalled by Right-click > Uninstall in Device Manager and rebooting computer. It is best to locate (or download) motherboard drivers to have them ready if Windows asks for them after reboot.
One of the more confusing issues when you first encounter it, mostly because Windows is completely silent about such enforced mode changes.
But it is common, easy to detect and relatively easy to fix. I wish more errors were like this. :)