NCR 53C9x

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 53CF94 and 53CF96 added SCSI-2 support and implemented larger transfer sizes per SCSI transaction.

All members of the 53C94/96 type support both eight and 16 bit host bus transfers via programmed input/output (PIO) and DMA.