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COMPUTER BITS ■ BY PAUL LYNCH A look at hard disc drives Almost everyone who owns a PC has a hard disc drive. Here's how to get the best out of it & protect your valuable data. Everybody tells you that your hard disc is going to crash one day. In fact, some of the things you might do can make this more likely. If you move your computer while the hard disc is spinning, you improve your chances of a crash. You do the same if you're in the habit of switching your computer off and on quickly to reboot it. (If you need to reboot quickly while you're running, press Control-Alt-Delete simultaneously or, if your computer has one, press the Reset button on the box). Discs are also more likely to crash in dirty environments. Keep your pets away from the CPU, especially if they want the warmth and shed hair. And don't leave your computer just inside There are not very many people with the patience and the required large number of floppy disks handy to regularly back up, say, a complete OS/ 2/2 .0 (30Mb) or Windows 3.1 (10Mb) installation. Of course, if you have nothing but kosher software in your machine, you don't need to back up those large installations because you have your legal disks at hand, ready to use in time of trouble. All you need back up are your data files - your spreadsheets, letters, reports, manuscripts and so on. But even if you do this meticulously, you still place a lot of faith in your hard disc. If you buy the wrong one when you buy a computer, you will find yourselfin serious difficulty hours of accumulated seconds and minutes while you wait for your data to jump back and forth between hard disc storage and memory. And, of course, some hard disks do crash, although if you follow the practice of updating your equipment (ie, buying a new computer) every three or four years, this is not very likely to happen to you. Hard disks from leading manufacturers are a great deal more reliable today than the one that crashed on me in 1984. Come to think of it, the manufacturer of that device has since gone out of business. Hard disc controller Your computer can run without a hard disc and even inside the box, the hard disc is a separate device. Accordingly, most hard disc-equipped computers come with a dedicated board - the controller - that plugs into the motherboard. Since almost every PC user today wants a hard disc as well as at least one floppy drive, most hard disc controllers are designed to connect your CPU with all your data drives. They do this through "If you move your computer while the hard disc is protocols known as interfaces. If you change hard drives for any reason and spinning, you improve your chances of a crash. the new device has a different interYou do the same if you're in the habit of switching . face, you'll need a different hard disc your computer off and on quickly to reboot it". controller. The first hard disc interface for most PC users in the not-so-good old days an open window if you live in dusty fairly soon - in most such cases, dif- was named ST506. Back then, we or industrially hostile environments. ficulty based on the fact that the disc thought that all hard drives were miraAnother thing everybody tells you you bought is too small for what you cles and we had nothing to compare about hard disks is that you should wantto put on it. In 1992, think 100Mb them with, so it took some time for us back up your data on them regularly. minimum. to understand that hard disks didn't This is getting harder and harder to Other difficulties can arise if you need to be that slow. Those early units do using the traditional technique (ie, buy a slow hard disc when you plan had slow seek times and were slow in copying the hard disc contents to a to run hard disc-intensive applica- transferring data (seek time is the time set of floppies) because the latest soft- tions. While you won't actually be it takes for the disc head to find the ware takes up so much space. This sitting on your hands much of the track you want). calls for a lot of floppies. time, you can expect to log hours and The ST506 disc type had certain 32 SILICON CHIP TRACK -T CYLINDER _J STOCK SALE!! FANS 80 x.80 x 25mm 240VAC .... $16.84 120 x 120 x 38mm 240VAC $16.92 Fan Finger Guards for 80mm Fans ....................... $1.43 Fan Finger Guards for 120mm Fans .. ................... $2.12 MISCELLANEOUS Fig.1: how a hard disc is constructed. It consists of a number of platters stacked vertically on a spindle to form a cylinder. Four platters are shown here but this can vary according to the manufacturer & the capacity of the drive. other problems. For example, if you needed to move your ST506-equipped computer, you had to type in a special DOS command at your DOS prompt to "park the head". If you didn't do this, the head could bump the disc while you were moving your machine, destroying or scrambling the data at the point of contact. Few of us who moved into PCs in recent years have ever parked a hard disc, since later protocols do that automatically every time you shut down. ST506 hard disks are virtually unobtainable today and if you have an old machine with such a drive, and want to replace it, you will almost certainly find yoµ're choosing from IDE (integrated drive electronics), ESDI (enhanced small device interface) or SCSI (small computer system interface) disks and controllers. All these interfaces offer shorter seek times and faster data transfer. SCSI is generally chosen for the larger hard discs - up to 2 or 3 gigabytes and it comes with the possibility of serious problems for you. Different manufacturers implement different options in the SCSI specification and this means that you may have compatibility problems installing a SCSI device. Make sure that your system is working well before you accept it. IDE disks make up a large part of the 40Mb-200Mb devices that are now the main market for PC hard disc drives. But it seems that ESDI and SCSI offer more opportunities for technical development, which means IDE disks may be a vanishing breed. If you have an old ST506 disc and would like to put more information on it, you may be able to do that simply by changing your controller. In recent years, two ways of encoding binary data on hard disks have built on the original FM recording technique. Modified FM (MFM) doubled the FM data density and run length limited (RLL) has •increased it even further. An RLL controller can change a 20Mb disc into a 30Mb disc at little expense - if the disc is RLL-compatible. To check this, track down the local agent for your disc and get an authoritative opinion about its compatibility. Hard disc structure You may have wondered how it is that a hard disc holds so much more information than high-density floppies. Part of the answer comes from the fact that the typical hard disc is not a single disc at all. It's a set of discs called platters, mounted centrally on a spindle to form a cylinder - see Fig.1. There's space between each pair of platters to allow room for the dedicated head that each platter needs. Each platter is arranged like a floppy disc, in that it has a number of concentric magnetically-surfaced rings called tracks, and each track is di- Circuit Breakers 7.5A- Press To Reset ... .. ....................... $7.25 Mains Power Lead 10A 1.8m long ........................... $4.16 9V Battery Snaps .................. $0.20 2 x AA Battery Holder ............ $0.28 12-Way terminal block 10A ... $1.60 SEMICONDUCTORS 1N4004 Diodes ..................... $0 .07 1N4007 Diodes ..................... $0.1 O 1N4148 Diodes ..................... $0.04 MJ15003 Transistor .............. $6.50 MJ15004 Transistor .............. $6.50 MJ 15024 Transistor .............. $8.60 MJ15025 Transistor .... .. ........ $8.60 MJ13007 Transistor .............. $4.87 MFR571 Transistor ............... $4.27 NE555 IC ........ ... ................... $0.30 TL494 IC ........................... .... $2.83 MC14514 IC .. .... .................... $3.00 MC34063 IC .. .. ...................... $2.98 ALL ITEMS 10 PLUS 10% OFF HYCAL ELECTRONICS Unit 4, 62 Gt. Western Hwy, Parramatta, NSW 2150. Pho11e (02) 633 5477 Fax (02) 891 5640 Credit Cards Welcome JUNE 1992 33 MASSIVE TEST EQUIPMENT SALE The following equipment is surplus to requirements and is now offered for sale. Most prices are negotiable. HEWLETT PACKARD 8064A Realti me Audio Spectrum Analyser. 50Hz-1 0kHz. For specialised vibration & acoustic measurements. As new, $2000. Manuals available from HP. HEWLETT PACKARD 5245L Frequency Counter 50MHz. Plug in converters to 12.4GHz available (not supplied). Clean & operational, $350 - 2 available. Service & operator's manuals supplied. · HEWLETT PACKARD 5253B Frequency Counter Plug In. 500MHz. Clean & operational, $300. Service & operator's manuals supplied. HEWLETT PACKARD 11 036A Probe. Suit 41 0C RF Voltmeter. Clean & operational. $100 HEWLETT PACKARD 53278 Timer/ Counter/DVM. Clean & operational. No manual, $300. AWA U210 and U209 Universal Ca- pacitance Box, 10nF to 10µF. And 1nF to 1µF. $20 each. AWAA412 VHF FM Test Set, clean with manual. $300. AD-YU ELECTRONICS 422A Video & RF Phase Meter, $250 clean. AWA E260 True RMS Voltmeter, clean, operational, with manual. $180. HEWLETT PACKARD 200CDR Wide Range Audio Oscillator. $120 clean. HEWLETT PACKARD 8755A HEWLETT PACKARD 675a Signal Generator/Sweeper 32 MHz. As new $750. Service and operator's manuals supplied. 676A Phase/Amplitude Tracking Detector to suit above - as new $400. Swept Amplitude Analyser Plug-In. Suits HP180/182 Mainframe. $200 clean. WAYNE KERR B224 Universal Bridge. Clean, with manual copy. $450. MARCONI TF2330A Analyser 76KHz. Clean & operational $350. Service/operator manuals supplied. HEWLETT PACKARD 1740A 100MHz Oscilloscope with service & operator's manual , $1250.00 AMRITSU MG54B Signal Generator/Test Set 480MHz FM. Clean & operational $250. DRANETZ 3100 Sampling Network Analyser. Complex Measurements to 2MHz. Incorporates 20-column printer. As new $3500. Service & operator manuals supplied. AMERITEC AM48 Hand-Held Personal Transmission Test Set with service & operator's manual. $1000.00 SEKOMIC SS 100 Single pen rack mount chart recorders. 2<at>$150.00 SIEMENS K2001 Level Tracer. TEKTRONIX 100MHz Oscilloscope. Rack mount, blue screen, clean & 200Hz - 4kHz with manual. Clean and operational. $500.00 operational, no manual, $750. SIEMENS D2008 Level Meter. TEKTRONIX 50MHz Oscilloscope. Clean & operational. $500. 200Hz - 18.6MHz. With manual, clean and operational. $750.00 Please call, write or fax: AV-COMM PTY LTD, PO BOX 225, BALGOWLAH 2093 Tel: (02) 949 7417 Fax:(02) 949 7095 34 SILICON CHIP vided into sectors. If you know how to look into your BIOS, you will find recorded there the disc capacity, the number of heads (and platters), the number of cylinders, and how many sectors there are on each track. The meaning of the word "cylinder" here differs from normal. A hard disc cy 1inder is a vertical stack of tracks in the same position on all platters. No hard disc is ready for use until it has been formatted. The manufacturer supplies the disk already low-level formatted - ie, its tracks and sectors are in place. These can be changed if you wish but it's a task for an experienced operator. Either you or your dealer then supplies the high-level format that lets the disc recognise the information you want to send it. Most disks are high-level formatted using MS-DOS, which tells the disc where it wants the boot sector, the file allocation table and the root directory. During the high-level formatting process, the PC operating system may find blemishes on the surface of the hard disc and will cross them out of the book of the living - they become known as bad sectors. In fact, many hard disks have a small number of bad sectors due to manufacturing faults. If, after some time, your diagnostic software reports that the bad sectors are increasing in number, it's time to seek professional help. You may be heading for a crash. When hard disks were slower some years ago, interleaving tweaks were often used to improve performance. If you adopted a 3:1 interleave, the hard drive head would read only every third sector on each disc rotation. Faster processors and faster disks mean that this early tweak is no longer much of a help. Most hard disks are now supplied with a 1:1 interleave and, usually, that's the way they should stay. Always remember that your computer believes your hard disc is whatever you've told it. You can format it simply as drive C. Equally, you can format it as a whole lot of different drives, using DOS, and there are many reasons to tell your computer there's more than one drive in there. The "extra drives", of course, make no physical change to the disc and they are called, a little confusingly, "logical drives". If you install OS/2 version 2.0, you can set up your computer to boot from either OS/2 or DOS. Obviously, to do this, you need two Speeding Up Your Hard Disc DOS was designed when drives were small and speed not highly regarded. As a result, it packs data onto your hard and floppy discs in a way that uses up the least space but isn't all that quick to unpack when you need it. As a result, every time you use your hard disc, it gets a little slower. If you haven't been using a disc defragmenter, it's likely that you're running much slower than yo\,J have to. This is a funny name - what's defragmented is your files, not your disc. The best-known disc defragmenters come with Norton Utilities and PC Tools, which each cost about $200. They do make your disc retrieve information faster. If you want to do the same thing for free, you can back up everything on your disc to floppies, reformat it, and restore all your files. This can take an astonishing length of time. Here are some more things that you can do: (1). Optimise your buffers: buffers are parts of your memory that store data temporarily during information transfer. MS-DOS and DR DOS allot what their manufacturers think is the best number of buffers for the hardware you have - both softwares can detect your configuration during installation. If you have a large hard disc, increasing the number of buffers can speed your work. You do this by changing CONFIG.SYS. On the other boot sectors and you can't have two sectors on one drive. This is one reason to format your hard disc with at least one logical drive. Your particular software may need special partitioning and extra drives. Its documentation will explain why and how to achieve it. Glass discs The hardware is also changing. The first mass-produced glass discs are expected on the market later this year, replacing the earlier metal platters. Also this year, we could see the first discs which leave the head in constant contact with the platter, eased by a lubricating liquid layer. Since a head crash is what happens when the hand, if you use disc caching (see below), you should minimise the number of buffers, perhaps down to one or two. (2). Weed your directory path: your AUTOEXEC.BAT file contains a line that starts with the word PATH. Organise this so that the programs you use most often are at the start of the list of directories that follows- first your root directory, then DOS, then ... well, what do you use the most? When DOS is looking for the start of any file you ask for, it starts at the beginning of your path, and works along it, directory by directory. It's amazing that it gets through so much work. By reorganising your path, you can reduce the work and time. (3). Add a disc cache: there are two types - hardware and software. The hardware devices are expensive and many do not work much faster than the cheaper software. Disk caching is the best way to speed your hard disc. Microsoft offers its software cache, SMARTDRV.SYS, with MS-DOS 5.0 and Windows - which makes it, in effect, free. PC Tools, mentioned above, includes a cache, as does DR DOS. The best-known standalone software cache is the highly-regarded PCKwik. Software caching takes part of your hard disc's contents and puts it in RAM, which works much faster, usually because it holds onto the data you've accessed most recently. head hits the platter, a design which leaves the head and platter in contact all the time will end the era of the head crash. If you really can't get by without the stuff on your hard disc, and you don't have the time or perhaps the self-discipline to back up to floppies , you can install a second hard disc and back up the data from your original hard drive to it. Most desktop designs can accommodate a second hard disc and there is usually a vacant slot on the motherboard for a second hard disc controller. This makes backup a very simple process - provided your backup disc is at least as large as your primary hard drive. SC Ian J. Truscott's ELECTRONIC WORLD 30 Lacey Street, Croydon, 3136 Phone (03) 723 3344 Fax: (03) 725 9443 Mail & Credit Card Orders Welcome **** NOW ALSO AT COLLINGWOOD •••• ** 200 Smith St (near PO) •• ** Phone: (03) 419 8208 •• We stock an extensive range of semiconductors, FETs & Mosfets, power & zener diodes, SCRs, Triacs, Linear ICs, 74LS/HC & 4000 series IC's, high-intensity LEDs and displays. Accessories inc. pots, trimpots, RF chokes, voltage regulators, relays, fuses, globes & heatsinks, as well as a comprehensive range of many popular switches, knobs, plugs & sockets. We offer a huge range of resistors & capacitors and popular parts at competitive prices. Rechargeable batteries, both regular, tabbed, rapid charge and back-up types are available ex stock. Ring for a price on our sealed lead-acid, video, cellular phone and watch batteries. We now offer a speedy, courier delivered, mail order service. HI-FI & PA SPEAKERS Huge variety of all common hi-fi replacement speakers, crossovers, speaker cloth & grilles. Call for a price on our great range of speakers, microphones, cables, audio leads & adaptors - we'll send you a catalogue. 2-way crossovers (pair) from $9 3-way crossovers (pair) from $16 SWF1212" 100 watt RMS woofer $75 SWF8 8" 60 watt RMS woofer $39 Redford PECC 6.5" 60 watt woofer $38 Redford PECC 12" 160 watt woofer $114 DM40 4" 50 watt RMS midrange $16 DT30 1" 35 watt RMS dome tweeter $11 Ferro Fluid 30 watt (60 max) tweeter $13 Piezo tweeters from $16 Speaker wall mounts from $39 2-way speaker switch boxes $18 3-way speaker switch box (impedance matching) $49 Don't forget our disposals store at Sth. Croydon. There's plenty of hard-to-find parts and help you won't get elsewhere! Phone 723 2699 (ask for Mai) JUNE 1992 35