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ATA/IDE
The terms ATA (advanced technology attachment) and IDE (integrated drive electronics) are often used interchangeably, but are distinct properties. ATA is the parallel interface used in home and office computer workstations, while IDE more specifically describes controller technology integrated into a drive's logic board.
UDMA
A data transfer protocol added to ATA, UDMA provides data integrity (via a
CRC check) and much higher data transfer rates. UDMA offers faster performance through higher burst rates (how fast the drive can transfer data across the bus), although, the media transfer rate of the drive (how fast it can read and write to the disk media) limits true performance.
UDMA increases the speed of large data transfers. By taking the burden off the CPU, UDMA mode is substantially more efficient than
programmed input/output (PIO) mode.
PIO
In PIO mode, the systems microprocessor gets involved in transferring the data from or to the storage device to or from system memory through the input or output ports. In DMA mode, the job of transferring the data is handed over to a bus-mastering system controller called the DMA controller. The DMA controller is set up or programmed to handle the DMA transfer. This relieves the processor from the duty of performing the data transfer so it can do other tasks.
UDMA Specifications
- UDMA 2: 33 MB/s.
- UDMA 4: 66 MB/s.
- UDMA 3: 45 MB/s (never produced).
- UDMA 5: 100 MB/s.
- UDMA 6: 133 MB/s.
Note, there is no UDMA 1 specification.
Enabling ATA DMA on Windows-Based Systems
Tip: start troubleshooting an ATA drive performance issue by checking that DMA is set up correctly.
Depending on the operating system, PIO mode may be set by default. For performance reasons, we recommend that you make sure that DMA is enabled.
Checking DMA Using Windows XP and 2000
- Right-click on My Computer and select Manage.
- Click the “+” sign next to System Tools.
- Select Device Manager.
- In the right pane, click the “+” sign to expand the list of IDE ATA/ATAPI Controllers.
- Double-click on the appropriate channel for your drive (primary, if it is your boot drive).
Checking DMA Using Windows 95, 98 and ME
- From Device Manager, select Devices by Type from the View menu.
- Click on the “+” sign to the left of Disk Drives. This will expand the list of drives and show the hard disk drives that are installed.
- Right-click on the drive in question and select Properties.
- Click the Settings tab.
- In the Options section, make sure there is a checkmark to indicate that the system is using DMA.
- Click OK.
The IDE Channel Properties dialog will open as shown below.
- Click the Advanced Settings tab.
- Change Transfer Mode selection to "DMA if available."
The IDE Channel Properties dialog shows the Advanced Settings tab, as shown below.
- Click OK.
You may want to run a third-party performance utility to check the CPU utilization rating. DMA mode is usually around 5-10 percent but can be as high as 20 percent. PIO is usually around 80-90 percent but can be as low as 40 percent. In-between ratings are not an issue.
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