UltraSCSI

UltraSCSI refers to a family of parallel SCSI interface standards that significantly increased data transfer rates compared to earlier SCSI versions. The first major iteration was UltraSCSI, also known as Fast-20, which doubled the transfer rate of Fast SCSI to 20 megabytes per second. This was achieved by using a higher clock speed. Following this, UltraSCSI evolved into UltraWideSCSI, which combined the faster clock speed with a wider data bus (16 bits instead of 8 bits), further doubling the theoretical bandwidth to 40 megabytes per second. The next step was Ultra2SCSI, also known as Fast-20LVD, which introduced Low Voltage Differential (LVD) signaling. LVD allowed for longer cable lengths and higher speeds, reaching 40 megabytes per second in its single-ended (SE) variant and 80 megabytes per second with the wider Ultra2WideSCSI. The final significant development in this lineage was Ultra3SCSI, known as Ultra160 SCSI. This standard introduced Differential Signaling and Double Transition (DT) encoding, effectively doubling the transfer rate again to 160 megabytes per second. Subsequent standards like Ultra320 SCSI further increased performance to 320 megabytes per second, building upon the technologies introduced in Ultra3SCSI. UltraSCSI interfaces were commonly used in servers and high-performance workstations for connecting hard drives, tape drives, and other storage devices before being largely superseded by serial interfaces like Serial Attached SCSI (SAS) and Serial ATA (SATA).