8 Troubleshooting

This should get a prize for the PC compatible's most obscure error message. It usually means you haven't made the primary partition bootable or, in Microsoft-speak, 'Active'. Use FDISK to fix this. Don't fret, you won't have to repartition or reformat anything unless you have no primary partition at all.

The earliest true-blue PCs had a BASIC interpreter built in, just like many other home computers those days. Even today, the Master Boot Record (MBR) code on your harddisk jumps to the BASIC ROM if it doesn't find any active partitions. Needless to say, there's no such thing as a BASIC ROM in today's compatibles, and this action ends in the above error message.

If your 4.50G BIOS is dated earlier than 12/13/1994, the address translation table is faulty. To access drives with more than 1024 cylinders, you cannot use address translation (Large) but must use LBA. In versions dated 12/13/1994 or later this has been fixed. Be warned that switching to LBA will probably force you to repartition and reformat your drive; do back up your data.

Many BIOSes dated before 1996 contain bugs making them incompatible with drives of more than 4096 cylinders, which works out to be about 2GB in size. Some BIOSes have similar problems at the 8192 cylinder boundary (4GB). The effects may range from not being able to use the full capacity to a crashing BIOS during bootup or upon detecting the drive.

Possible solutions include

• a flash BIOS update, if you've got a flash BIOS and your board manufacturer makes a fixed BIOS image available;
• non-flash BIOS ROM ugrade;
• a software disk manager like using OnTrack Disk Manager or EZDrive;
• if the BIOS allows a user definable drive type, manually setting the cylinder count to 4095 (8191). This means you can use no more than the first 2GB (4GB) of the drive.

Some BIOSes assign a drive of over 8192 cylinders a translated geometry with 256 heads. MSDOS 6.22 and below fail when they try to access the last head.

If your BIOS allows a user definable drive type, use a geometry with 15 heads and 16/15 times the original number of cylinders, rounded down. Thanks to universal translation you can always do this. Remember to write down the geometry somewhere so that you can reproduce it if necessary! If no user definable drive type is possible, there's little you can do about this except upgrade to Win95.

Try using a slower mode or disable fast modes altogether. Mode 3 and especially mode 4 are very sensitive to timing problems, and not all adapters follow the ATA-2 specification really closely. Don't dismiss the possibility too easily: if you changed anything on your system, it is very well possible that a drive which marginally worked so far now starts to corrupt data.

Some controllers seem to configure themselves according to the capabilities of the master drive. This can mean trouble if the slave handles only slower modes.

No. All modern drives support error management, which completely hides any bad sectors that may be on the disk before leaving the factory. Even a single bad sector is sufficient grounds to return the drive under warranty. If you want to continue using it, the drive should be viewed with the utmost suspicion.

Western Digital's wdat_ide.exe utility can hide grown bad sectors on many Caviar disks.

There is one exception. Under rare circumstances, use of bad (too fast) timing by the disk adapter can cause bad sectors on a disk. This type of error can be fixed simply by writing fresh data to these sectors, as there is no actual media defect.

There appears to be an awful lot of confusion about this subject, partly due to some unhappy terminology.

In the most literal sense, no ATA(-2,-PI) drive will allow 32-bit access. Data is transferred to and from the drive over a 16 bit bus. However, many local bus interfaces are capable of combining two 16-bit words into a 32-bit doubleword when reading data from the disk, and the reverse when writing. This way, data transfer between the CPU and the interface can be done in 32-bit chunks. This is often called '32-bit access', although '32-bit host bus transfers' would be a better name.

There are numerous reasons why this can fail; you will more easily be able to do something about it (or decide if you want to fix it in the first place) once you know some background.

Windows' 32-bit disk access (32BDA) is a bit of a misnomer, actually, since it has nothing to do with 32-bit data transfers. A slightly better name for it is 'FastDisk'. It is a feature of Windows in 386 Enhanced mode that allows one to replace the BIOS' disk routines by Windows' own routines that work in protected mode. A much better name, then, would be "protected mode controller access". For some reason Microsoft decided not to use the latter.

Anyway, the main advantage of this feature is that it allows Windows to use virtual memory for its DOS sessions. Without 32-bit disk access, DOS sessions cannot be swapped out and every DOS box takes 640k of real memory. Because it also reduces the number of switches between virtual and protected mode Windows has to make, it gives a slight performance improvement as well, but usually nothing dramatic. Only if 32BDA is used together with Windows for Workgroups' 32-bit file access feature, it will eliminate these mode switches altogether (at least for most disk operations), which gives a far more interesting performance boost.

Unfortunately, the standard FastDisk routines that are internal to windows, called *wdctrl, are severely limited in their capabilities. The *wdctrl software understands nothing of non-IDE hardware (e.g. SCSI), more than two harddrives, drives with more than 1024 cylinders, 32-bit host bus transfers, block transfers, or ATAPI CD-ROM drives on the primary channel. If you use any of these things, 32-bit disk access won't work unless you have a *wdctrl replacement.

Today, that means that 32-bit disk access won't work 'out of the box' for most of us.

The idiosyncrasies of the 32-bit disk access feature with respect to disk hardware has led to the popular myth that 32-bit file access has similar problems. However, that's all it is: a myth. If 32-bit file access fails, you should first check your filesystem and the programs that use it. As little as a single open file, e.g. from a printer spooler, will cause 32BFA to fail. Oh, and put DEVICE=C:\WINDOWS\IFSHLP.SYS in your CONFIG.SYS, and make sure your SYSTEM.INI contains the correct magic incantations (vfat.386, vcache.386). If this doesn't help, there's a first rate FAQ on this topic (see the net.resource guide for details).

The culprit usually is a virus. Do get a recent virus scanner.

If that turns out negative, it may also be DOS (real-mode) driver that loads in the CONFIG.SYS or AUTOEXEC.BAT, or an old version of EZDrive/Disk Manager loading from the MBR.

See the next question.

If you've used Win95's fdisk utility to partition your drive, you may run across a nasty bug.

Win95 supports extended int13 calls to break the 8GB barrier. To avoid problems with old versions of DOS, partitions extending beyond 8GB must be made invisible. Unfortunately, the Win95 FDISK sometimes hides partitions this way even if your drive is much smaller than 8GB. Incidentally, this also hides them from all other operating systems, including old versions of DOS, and can cause all kinds of problems.

Under circumstances, these new partition types can completely mess up things when going from the Win95 graphical shell to MS-DOS mode. Drive contents may appear to be corrupted or be replaced by the contents of C:. Don't try anything fancy when this happens; it is really easy to corrupt your data. Don't use the "Restart in MS-DOS mode" option and don't run programs configured to run in MS-DOS mode. MS-DOS windows are still fine.

If you have a Triton II or Natoma based board, the retail version of Win95 may not recognize the PIIX3 interface. This will trigger an entertaining bit of Plug'n'Pray magic which eventually causes the BIOS to disable the secondary IDE channel on the next reboot.

To determine if this is really your problem, go into the device manager and click on Hard Disk Controllers. If you see the following devices listed:

• Primary IDE Controller (single FIFO)
• Standard Dual PCI IDE Controller
• Standard IDEESDI Hard Disk Controller/

The Win95 busmastering drivers sometimes have trouble co-operating with older harddisks and ATAPI CD-ROMs. Try installing the latest drivers.

If that doesn't help, you could try this registry hack. Move all old devices to the secondary port. Back up the registry (system.dat and user.dat in the Win95 directory). Start regedit and look for

HKEY_LOCAL_MACHINE/System/CurrentControlSet/control/Services/hdc

If the CD-ROM is connected to the secondary channel, make sure this channel is enabled. Some BIOSes will enable the channel only if one or more harddisks using this channel are defined in the setup; in that case, you can't avoid putting the CD on the same cable as a harddisk until you manage to get your BIOS updated.

You may also get trouble if the CD-ROM is jumpered as slave and there's no master on its channel.

Finally, the PIO mode (speed) used by the interface may be too high, especially if the CD-ROM shares its cable with a harddisk. Many interface drivers and BIOSes are not ATAPI-aware and don't take the CD-ROM into account when determining the maximum possible speed. The best fix is to move the CD-ROM to a different channel. Manually lowering the mode a notch or two should also help; this is usually done either through the BIOS setup or by passing options to a device driver in the CONFIG.SYS.