DS8921MX are Differential Line Driver and Receiver pairs designed specifically for applications meeting the ST506, ST412 and ESDI Disk Drive Standards.
DS8923AN are Dual Differential Line Driver and Receiver pairs, the devices are designed specifically for applications meeting the ST506, ST412 and ESDI Disk Drive Standards.
DS8923AM is a Dual Differential Line Driver and Receiver pairs, these devices are designed specifically for applications meeting the ST506, ST412 and ESDI Disk Drive Standards.