IBM Corp stores 4Mb on a 5.25 logical drive by mounting two 3.5 drives into a 5.25 enclosure, but Chatsworth California-based Micropolis Corp has come close to the same capacity in a conventional 5.25 drive, the 1936, which stores an unformatted 3.6Gb, and offers data transfer rates of up to 20 Megabytes per second. It comes in four versions – an 8-bit Fast SCSI-2 model offered with a single-ended SCSI interface; An 8-bit Fast SCSI-2 model with a differential SCSI interface; a 16-bit Wide Fast SCSI-2 interface model; and a Concurrent Dual Port Wide Fast SCSI-2 interface model. The Fast SCSI-2 models deliver transfer rates of up to 10 M-bytes per second, the Wide Fast drives double that speed. The average seek time is 12mS, the platters spin at 5,40rpm, and Multiple Zone Recording provides data capacity increase of up to 35% compared with single frequency drives. All four new models feature Tagged Command Queuing to increase throughput by optimising the seek and latency of multiple commands; Multi-Segmented read-ahead cacheing to enable frequent and multiple accesses to be served from the 256Kb cache buffer for improved read performance; and zero latency to provide further performance through low command overhead. The Micropolis Intelligent Concurrent Wide Fast Dual Port model enables each host to communicate with the drive and queue commands or data during input-output activity, while simultaneously transferring data through a dual-ported data buffer so that the drive can be accessed by two separate hosts through a dedicated port from each host where traditional dual port designs provide access to the drive through one of two ports, placing the inactive port on stand-by until an on switch is activated. Micropolis has begun OEM production shipments of the Fast SCSI-2 model. Evaluation units of the Wide models are available, with Dual Port availability in January; production shipments of all four models will ramp during the first quarter. Single unit prices are $4,900 for the single-ended or differential Fast SCSI-2 models, $5,000 for the Wide Fast SCSI-2 model and $5,200 for the Wide Fast SCSI-2 Dual Port.
