Compatibility Between Old and New IDE Devices
With only minor exceptions, there are no compatibility issues when using new ATA devices with old ATA interfaces or vice versa. Newer drives cannot yield their highest performance when connected to an ATA interface that does not support the fastest transfer modes the drive is capable of, just as a new interface can’t improve the performance of an older drive. But you can connect any ATA drive to any ATA interface with reasonable assurance that it will function, although perhaps not optimally.
Nearly all modern ATA interfaces—including the ubiquitous Intel PIIX3 and PIIX4—support independent timing for Master and Slave devices. This means that you can safely put an old, slow ATA or ATAPI device on the same cable as a new, fast hard drive without concern that the older device will cripple the throughput of the newer one.
Warning
Note that independent timing does not mean that you should mix DMA and PIO devices on the same interface. If an interface has one PIO-mode device connected, the other device must also run PIO. Also, independent timing does not mean that an interface supports multiple DMA modes simultaneously. For example, if you connect an ATA-66 drive and an ATA-33 drive to the same interface, both run as ATA-33 devices.