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The NCR 53C9x is a family of application-specific integrated circuits (ASIC) produced by the former NCR Corporation and others for implementing the SCSI (small computer standard interface) bus protocol in hardware and relieving the host system of the work required to sequence the SCSI bus. The 53C9x was a low-cost solution and was therefore widely adopted by OEMs in various motherboard and peripheral device designs. The original 53C90 lacked direct memory access (DMA) capability, an omission that was addressed in the 53C90A and subsequent versions.
The 53C90(A) supported the SCSI-1 protocol, implemented the eight bit parallel SCSI bus, and eight bit host data bus transfers. The 53C94 added SCSI-2 features to those of the 53C90A, and the 53C96 added support for the high voltage differential (HVD) parallel bus. The 53CF94 and 53CF96 also implemented larger transfer sizes and 20 MB/second synchronous SCSI bus speed (the so-called ultra-SCSI protocol). All members of the 53C94/96 type support both eight and 16 bit host bus transfers via programmed input/output (PIO) and DMA.
QLogic FAS216 and Emulex ESP100 chips are a drop-in replacement for the NCR 53C94. The 53C90A and 53C(F)94/96 were also produced under license by Advanced Micro Devices (AMD).
A list of systems which included the 53C9x controller includes:
53C94
53C96