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COMPUTER BITS By JENNIFER BONNITCHA What to do when your computer goes bung; Pl.3 Faulty disc drives are a common cause of computer malfunction and can lead to loss of data or even complete files. Similarly, it's all too easy to unintentionally delete wanted files. Here's what to do when disaster strikes. Computers and accidents were made for each other so backup your data regularly. I know that you know that DEL*.* is something only simpletons do. Likewise FORMAT C: ~ you would never do something so ridiculous would you? Don't bet on it. Everyone has moments of stress, anxiety and just plain stupidity. If (read when) the inevitable occurs, reach for one of the excellent software utilities containing an "undelete" program. Mace Utilities, PC Tools and Peter Norton's Norton Utilities are probably the best known but there are many other highly reliable programs available both commercially and in the public domain. These programs also often contain software which will undelete a formatted disc. If you accidentally delete files don't do anything more with that disc until you can run a utilities pro- gram. If you have a hard disc, find the most recent set of backup discs and use them. If you work in a floppy disc only environment, always make extra backup copies. The floppy disc is no less susceptible to corruption and data loss than the hard disc. Following a hard disc disaster, some companies elect to store all data on floppy discs. This is fine except that they usually make no provision to backup the diskette contents, leaving them just as vulnerable but on a smaller scale. Viruses & the common cold When your computer catches a virus, it is usually the result of running an infected program on your computer. The system files like IQ . COM, DOS.COM and COMMAND.COM are favourite targets. Often the code can take control and destroy information on your disc. Vaccine programs exist to help detect these insidious heartbreakers. You should find that all reputable software is 100% virus free but be wary of public domain programs, particularly the games programs. System backups can sometimes help to eradicate the virus but it really depends on the type of virus your computer has caught. Hard disc head crash DON'T USE PAPER CLIPS to attach labels to floppy discs. The clips may have become magnetised and may destroy valuable data. Always hack-up your data and protect the discs from liquids, dust and fingerprints. 72 SILICON CHIP If everyone backed-up, imagine how peaceful life would be! Discs mostly fail for two reasons - old age and mechanical problems such as a head crash. A head crash occurs when the read/write heads touch the disc surface, thus scratching it and usually destroying forever the information on that part of the disc.) The heads themselves can also be damaged through carelessness, particularly when relocating your computer. Be sure to use your computer's pARK, RETRACT or sometimes SPINDOWN program to move the hard disc heads to a "safe" zone before the move. Voice coil drives usually park automatically when you finish using the computer. Parking - no, not that kind An alternative method of parking or locking the heads on some hard discs is an airlock feature which is activated when the power supply detects an interruption. Airflow is vital to disc operation. The cushion of air causes the heads to operate just above the surface of a hard disc and actually on a floppy disc surface (which is one reason why floppy discs don't last as long). \!\Then the computer is powered down, the read/write heads are parked and locked in a non-data area. A spring engages the airlock arm so that the heads remain in the non-data area until the airflow is once again sufficient. Some hard discs have their own kind of rubber shock absorbers. They suspend the head and disc assembly inside the hard disc case to provide protection from unexpected bumps and jolts. When a hard disc reaches the correct operating speed, a head actuator moves the read/write heads across the various platters. Stepper motor drives (the most common form of hard disc) move the heads in a series of steps from one track to another. The head actuators of the more expensive voice coil drive move the heads in one sweep to the right track using a magnetic field. Voice coil drives operate at around twice the speed of stepper motor drives. Hard disc hiccups A common indication of hard disc failure is the inability to boot the computer. At system startup, the BECAUSE THEY ARE MECHANICAL devices, disc drives eventually wear out and fail. In this drive, the read/write head (at end of pen) became detached from its support and damaged the floppy disc in the process. The discs themselves also wear out from repeated use. computer's BIOS performs a series of operations, culminating in a call to the hard disc for the final loading sequences. How you take the loss of a boot record depends a lot on your inner strength - and how long it has been since your last backup. Most problems with hard discs in particular can be traced to mechanical failures such as the stepper motor, worn out read/write heads, faulty drive controllers and faulty connecting cables. Sometimes the read/write heads and the platter surface can move slightly out of alignment. The end result is a disc drive which "thinks" it is reading from one track when in fact it is reading something completely different. The hard disc itself is just a recording device with connectors at the back for power and the hard disc controller board. It is the controller board which actually handles the task of formatting the disc for later use. It also "decides" where to place the read/write heads, where to write or read data, and when to report the success or failure of like operations to DOS. Generally the hard disc will experience one of the following problems: (1). Whining and screaming (no, not from the operator) from the hard disc. Make sure you backup your data now. Death is imminent. (2). Continual Abort Retry messages from DOS mostly indicate either operational problems (like typing the wrong command) or, when associated with drive specific!}tions, perhaps a damaged read/ write head. Run one of the diagnostic utility programs to show up any head errors. (3). Continual or increasing Abort Retry messages can also mean that bad sectors are causing problems. You could try running a low level format to lock out the bad sectors. (4). Sector or Address Not Found messages from DOS can indicate a chip failure on the logic board attached to the drive. The low level format is performed using the PC manufacturer's diagnostic or setup routines and it performs two important tasks. First, it sets the interleave for the disc and second, it formats every JULY 1990 73 sector on the disc to test it for reliability. Troublesome sectors are locked out by the controller to ensure that DOS can't store data in suspect sectors, no matter how hard it tries. The low level format also writes new sectors and sector ID headers but at the same time, like the DOS format, it overwrites existing information on the hard disc. There can be no recovery after the low level format but it can fix troublesome sectors. Frazzled floppies Some disasters are unavoidable but others can be avoided by using plain common sense. Take the humble can of soft drink - yes, take it right away from the computer. Any liquid, including tea or coffee, can mean death for floppy discs. Please be careful where you place the next cup, glass or can. I know you can all be adult about these things and can be trusted - but can you trust the other inhabitants of your office or home'? There is not a great deal you can do about spilt liquid except mop it up and hope for the best. A speck of dust, a biscuit crumb, cigarette ash, a drop of water and even fingerprints can all render a disc useless. Some disc manufacturing companies, recognising the frailty of human operators, offer disc recovery services. How they manage to resurrect some discs is close to a miracle. Liquids can affect more than discs (look around the office any Friday afternoon). Portable computers are often the victim of an untimely drowning. Their very nature means that they are often used balanced on the knees of their owners . Spilt liquid can cause a serious chain reaction in a laptop since liquid spilt ·on the keyboard drains straight into the system unit. Floppy disc drive alignment When you insert a disc into the floppy disc drive and close the latch, a spindle clamps the centre hold and starts turning the disc inside the jacket at between 300rpm and 360rpm depending on the disc type. A read/write head is also pressed 74 SILICON CHIP TABLE 1: FORMAT OPTIONS Disk Type Valid Switches 160/180K 320/360K 720K (5 .25) 720K (3+) 1.2M 1.44M /1 /1 /7 /N /N /N /4 /4 /V /T /T /T /8 /8 /S /V /V /V /B /V /S /B /V /S /S /S /S Formats a single side of the disc. /1 /4 Formats a 5.25-inch , doublesided disc in a high capacity disc drive. /7 Formats a 5.25-inch, 720K disc in a high capacity disc drive. /8 Formats 8 sectors per track. /8 Formats the disc, leaving enough space to copy an operating system. This was very popular in the good old, bad old days of software protection . /S Copies the operating system files. /T: Enables the specification of the number of tracks. This switch formats 3 + inch floppy discs to the number of tracks specified - 80 tracks for 720K and 1.44Mb discs (/T:80) . Specifies the number of sectors per track. The 3 +inch floppy disc formats the number specified ; for 720K discs, the value is 9 /N: (/N :9) . /V Format prompts you for a volume label at completion . against one or both sides of the disc. When all's said and done, it is most often use rather than abuse which spells the end for your floppy discs. The surface just wears out from a lifetime of having the read/write heads re-arranging the magnetic oxide coating. The most common problem with a disc drive occurs when it is out of alignment. One note of caution, however . If your disc drive is diagnosed as having an alignment problem, make sure you can read the contents of the discs on another machine. The discs can also be out a little and may read reasonably reliably on your disc drive but not on another computer. Preventative maintenance for discs Head cleaning kits are available for floppy disc drives. Generally they contain items such as antistatic cleaners, cleaning solution, dust removers, cleaning wands, cleaning wipes and a cleaning diskette. The value of these kits is debatable and falls into the same category as video head cleaners many manufacturers actively discourage their use. The best thing to do is to check with your computer's manufacturer. No cleaning at all is often preferable to over-zealous use of these products. Personally, I remain to be convinced of their worth, although I do know of some installations who swear by them - only you can judge. Disc capacity Two common problems with diskettes today are firstly the different sizes available and secondly, the different densities. While one 5.25-inch diskette may look like the next, they can be poles apart. Discs now come as either double density or high density. The problem is that while the double density disc traditionally has a capacity of 360K, the high density disc can have from 1.2Mb to 1.44Mb of storage space. In between, you can also find the quad density disc which stores 720K - although this is mostly confined to the 3 + inch format. You can only tell which does what by looking closely at the disc drive for an identifying label or by formatting a disc to find out the exact capacity. This procedure can, however, create further problems. Discs are upwardly compatible. This means the data on a 360K disc can be read by the high density drive but not vice versa. If you attempt to read a high density disc in a low density drive, depending on your DOS version, something like the following displays: General Error Failure. Error Reading Drive X. Abort, Retry, Fail'? Typically this indicates a wrong match of diskette and drive density. Check the disc label and, if available, format a blank disc, noting the results. Most computer manufacturers provide several options with the FORMAT command. Note that if you format single or double sided discs in the high density drive, you may not be able to reliably read those discs in their "native" drives. Table 1 is based on the options available on the NEC PowerMate: For example, the command: FORMAT A:/N:9/T:80 formats a 720K 3 + inch diskette in a high capacity 1.44Mb drive. You will also find that a lower density disc can format to a higher capacity in the appropriate drive. Although FORMAT will take a few tries to complete the process, you will generally find an increased disc capacity. Don't be fooled. Double density discs are not manufactured to the same standard as high capacity discs and usually contain some bad sectors. As the disc drive attempts to use those sec- tars, it retries the format operation many times. If your format program shows you the head and cylinder count, watch it next time you try to format' a double density disc in a high capacity drive. At completion, which can sometimes take a very long time as the drive tries to format those "dud" sectors, you will certainly end up with more available sectors. And you will almost certainly end up with ongoing problems. The disc drive won't use any bad sectors but it will attempt to use sectors which are only slightly better. It stands to reason that since the marginal sectors have a weaker signal, they will more than likely fail more rapidly. Since files are often segmented on a disc, you could also end up not being able to recover the rest of the file. In addition, the incorrectly formatted disc has data recorded at twice the recommended strength and density so that, over time, the adjacent magnetic domains on the disc begin to affect each other. What happens is that the disc seems to erase itself - although some would like to blame the ubiquitous computer virus. The result is inevitable - data loss which could be more than a little annoying. In addition, the low density disc is ruined since the high density format places a recording on the disc at twice the normal strength. You can try reformatting the disc in a low density drive but the drive cannot fully overwrite the stronger recording. Using the /4 format option in a high density drive is of little use since the high density drive goes into "reduced" mode to format at 360K. At this stage, you've got two choices. You can throw the disc away [what a waste) or you can put it through a bulk eraser which erases all magnetism from the disc and returns it to almost factory freshness. Next month, we'll look at the CHKDSK command and tell you what to do when errors are detected. We'll also take a look at power supply and keyboard problems. ~ Protect your valuable issuesl SILICON CHIP BINDERS These beautifully made binders will protect your copies of SILICON CHIP. In distinctive two-tone green high-quality vinyl specially selected for SILICON CHIP, and with heavy board covers, each binder holds a year's issues (the 14 issues of Vol.1 or the 12 issues of Vol.2). It will look great on your bookshelf. * High quality Hold up to 14 issues 80mm internal width Gold printed with SILICON CHIP logo on spine Price: $All.95 plus $A3 p&p each (NZ p&p $A6). Send your order to SILICON CHIP Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097; or use the handy order form on page 104. Fax 979 6503. ]ULY 1990 75