Hard Disk System

The Sirius 1 could be fitted with either an internal or external hard disc drive. Although it is similar in physical size (5¼ inches) to the floppy disc drive nearly nine times the amount of data can be stored (depending on drive size fitted) and the speed of data access is much greater than the speed of the floppy disc drive. Programs will run significantly faster and larger data files can be maintained.

Also known as the Winchester disc drive, a name coined by IBM in 1973 to describe a dual 30 megabyte disc configuration (30/30), Tandon Corporation became the initial supplier. Two different models may be encountered when servicing the hard disc, the TM502 or the TM603SE (other makes may be fitted) both of which are compact units that use a moving head, noncontact recording method with standard Winchester technology on a 130mm rigid medium. The storage medium is contained within the drive in a fixed, non-operator removable, configuration.

The hard disc subsystem consists of five major hardware components; the Winchester disc drive, Spindle and Motor Control Board, TM600 Main uP Board, Xebec Controller (pronounced zee-beck), and the DMA Interface Board.

The following information pertains to the TM502 and TM603SE:

The medium is rotated at 3,600 rpm +/- 1% by a direct drive brushless D.C. motor, giving an average latency of 8.3 milliseconds. Multiple track access time is reduced (TM502 drives only) by the use of an on-board 8748 microprocessor which calculates the optimum positioning algorithm.

Head positioning is by a split band, open loop, rotary positioning system. The track-to-track step time is three milliseconds plus fifteen milliseconds for head settling time after the last step of a seek. Heads automatically reposition to Track 000 at power up.

The drive reaches its operating speed 15 seconds after power is applied to the drive circuitry. Internal hard disc units reach operating speed 15 seconds after the power switch on the microcomputer mainframe is switched on. External hard disc units reach operating speed 15 seconds after the power switch on the external hard disc unit is turned on. In addition, the disc stops rotating within 15 seconds after power is removed from the motor drive circuitry. A solenoid-operated, mechanical brake is provided for rapid spindle deceleration, and to preclude the possibility of head or disc damage during shipping.

A self-contained, recirculating air filtration system supplies clean air through a 0.3 micron filter. A secondary absolute filter is provided to allow pressure equalisation with the ambient atmosphere without contamination. The entire head-disc- actuator compartment is maintained at a slightly positive pressure to further ensure an ultraclean environment.

The TM502 media consists of two (2) lubricated 130mm platters providing six recording surfaces.

The TM603SE media consists of three (3) lubricated 130mm platters providing six recording surfaces.

Storage capacities are listed in Table 1. Capacity is the maximum number of bytes that can be recorded irrespective of any gaps and formatting.

Table 1: Storage Capacities

Winchesters are delicate instruments that require proper care and handling. These units are expected to perform when needed. Misuse and/or mishandling will adversely affect the expected performance. The Winchester drive presents a new set of problems to the field in the sense that much care must be taken in handling the product. Because of the small size and light weight Winchesters are much more susceptible to damage. This product can be carried in one hand and is easily taken for granted, thus making it an easy candidate for unintentional exposure to high shock forces during handling.

1. The hard disc unit should be placed on a side or end when not in a system or shipping container.
2. Never drop or jar a hard disc unit, place the unit carefully on foam padding on work or storage surfaces.
3. NEVER TURN DAMPER OR SPINDLE MOTOR BY HAND !!

Designed for use in the end user's environment the diagnostic diskette HDFIELD will help the field engineer diagnose hardware and media related problems in hard disc systems. Whether the problem is with the hard disc subsystem or any of the other major subsystems of the microcomputer HDFIELD's primary objectives are to:

1. Determine if the hardware components are defective or degraded.
2. Determine the existence of defective hard disc media which is not currently logged in the drive header label.

NOTE: Users of the current Sirius Level 1 diagnostic disc (LEV1P) will experience a BDOS error if attempting to use that particular disc in a hard disc system. When this occurs (if you wish to use these diagnostics) simply type ALT C, and then log on to the B drive by typing B:

Following is a brief description of the programs which are included in the HDFIELD package that exercise the hard disc subsystem:

• SHOWSTAT reads the drive label and prints a summary of the label to the screen. This specifically includes a list of the current bad tracks. The distinction is made between bad tracks listed when the hard disc was initialised and those added after its initialisation. The number of bad tracks which have been added during normal usage should be monitored as an indication of disc drive performance degradation. Also displayed is the recorded serial number. Optionally, all displayed data can also be printed as hard copy output to the LST port.



• DMATEST tests the hard disc DMA interface to CPU board expansion bus. This testing is also performed in HDDISK under the DMA test (F2) option. The distinction is that DMATEST is limited to transferring data between the system main memory and hard disc controller memory. No drive access is performed.



• HDDISK is the hard disc test utility program. This utility allows the operator to test each component in the hard disc subsystem. The program is menu driven. The auto test (F1) is recommended as a start. If longer term tests are desired, either the random read (F5) or butterfly test (F6) should be executed. This program writes only to the pre-established inservice diagnostic track (if it can be identified).