PC Hardware in a Nutshell, 3rd Edition [Electronic resources] نسخه متنی

6.6 Working with Obsolete Diskette Formats

If you've been computing
for a long time, it's sometimes necessary to read a
diskette written in an obsolete format. You may also need to format
and write a diskette in an obsolete formate.g., to create a
boot diskette for an older system whose hard drive will not boot but
still contains valuable data. If you find yourself in such a
position, keep the following issues in mind:

A 3.5-inch 1.44 MB FDD can read, write, and format 720 KB (DD) and
1.44 MB (HD) diskettes. 3.5-inch 2.88 MB (ED) diskettes are readable
only by an ED drive. These are difficult to find new, so your only
option may be to locate someone with an ED drive who is willing to
allow you to use it to transfer your data.

A 5.25-inch 1.2 MB FDD can read any 5.25-inch diskette written with
an IBM format in any 360 KB or 1.2 MB drive. A problem may arise when
you exchange 360 KB diskettes between 360 KB and 1.2 MB drives. 360
KB drives write a wider track than 1.2 MB drives, which cannot
completely erase or format data put down by 360 KB drives. If a 360
KB drive formats or writes to a 360 KB diskette, a 1.2 MB drive can
subsequently read, write, or format that diskette, but once that
diskette has been written or formatted in the 1.2 MB drive, it will
no longer be reliably readable in a 360 KB drive. This problem does
not arise if the 360 KB diskette has never been written to in a 360
KB drive. Accordingly, if you need to write data with a 1.2 MB drive
that must subsequently be read by a 360 KB drive, use blank 360 KB
diskettes (bulk-erased, if necessary), and format them to 360 KB in
the 1.2 MB drive.

Old diskettes often have errors, either because the diskette has been
physically abused or simply because the magnetic domains on the
diskette have gradually faded with time. Reading data from a diskette
that was last written five or more years ago is very likely to yield
some read errors; a diskette 10 or more years old is almost certain
to have multiple read errors, and may be completely unreadable. Using
the diskette rescue utilities included with Norton Utilities for DOS
(http://www.symantec.com) and
SpinRite (http://www.spinrite.com) can often retrieve
some or all of the data from a marginal diskette.

If the data is critical, consider sending the diskette to one of the firms that specialize in data retrieval and advertise in the back of computer magazines. These services are not cheap and cannot guarantee that the data can be salvaged, but they do offer the best hope. If the data is important enough to pay a data retrieval firm to salvage, send the diskette to the company without trying to salvage the data yourself first. Running one of the utilities mentioned previously may render what would have been salvageable data unreadable by the data retrieval company.

You can generally
install a newer FDD in an older system and use it to emulate an older
FDD, with the following limitations:

The 5.25-inch 1.2 MB FDD spins at 360 RPM (versus 300 RPM for
all other FDDs) and cannot be used in a system whose FDD controller
supports only 360 KB FDDs.

You
can install a 3.5-inch 1.44 MB FDD in nearly any 286 or later
computers and some late-model XT clones, although the drive may be
recognized only as 720 KB. If that occurs, use 720 KB (DD) diskettes
in that drive. In theory, you should also be able to install a
3.5-inch FDD in a PC- or XT-class system and use it as a 360 KB FDD.
In practice, this works on some PC- and XT-class systems, but not
all. For reasons that are not clear to us, some old systems refuse to
recognize the 3.5-inch drive. If that occurs, your only alternative
is to locate an actual 5.25-inch 360 KB drive and use it to do the
transfer.

To use this method, you also have to temporarily reconfigure the 3.5-inch drive on the modern system to 360 KB in order to read and write 360 KB 3.5-inch diskettes. Some systems allow this, but others return a hardware error. Before you install the 3.5-inch FDD in the older system, check the newer system to make sure that it allows its 3.5-inch drive to run as a 360 KB 5.25-inch drive. To do so, run BIOS Setup on the newer machine, set the drive type to 360 KB 5.25-inch, and restart the system. If the system does not return a hardware error, insert a blank 720 KB (DD) diskette into the drive and issue the command format a:. If the diskette formats successfully to 360 KB, that drive is usable for your purposes.