Your SCSI-based Mac will not address an ATA drive unless you set up the ATA drive with a SCSI/ATA adapter. It was my belief that such adapters existed only for 2.5-in drives so that they might be used in PowerBooks—and even then they are scarce and pricey—when 2.5-in SCSI drives looked to be going out of production
We have to ask how you have managed to connect from a 50-pin internal ribbon cable (through Apple's economy 25-pin setup at the external port) to a 50-wire cable and (presumably) Centronics-style CN-50 peripheral connector to an essentially 40-pin HDD? One cannot refrain from supposing that an old Quantum LPS or Conner 3.5-in. external SCSI drive will give you fewer difficulties. That includes choices of enclosure, cabling and connectors.
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We have to ask how you have managed to connect from a 50-pin internal ribbon cable (through Apple's economy 25-pin setup at the external port) to a 50-wire cable and (presumably) Centronics-style CN-50 peripheral connector to an essentially 40-pin HDD? One cannot refrain from supposing that an old Quantum LPS or Conner 3.5-in. external SCSI drive will give you fewer difficulties. That includes choices of enclosure, cabling and connectors.
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