لطفا منتظر باشید ...
Publisher6.5 Working with FDDs
Keep the following issues in mind when working with FDDs:
3.5-inch HD FDDs are $10 commodity items made by several
manufacturers. We prefer the Teac FD235HF, but there is little
difference between brands. Buy whatever is offered. 5.25-inch FDDs
are still available, but that won't last forever. If
you need a 5.25-inch FDD to rescue data on old disks, get the drive
now. If you patronize a local computer store, check there first. They
may have a stack of old 5.25-inch FDDs they'd be
happy to give away or sell cheaply.
5.25-inch FDDs require a 5.25-inch half-height, externally accessible
drive bay. 3.5-inch FDDs can be installed in an externally accessible
3.5-inch third-height bay, or, by using an adapter, in a 5.25-inch
half-height bay. The BIOS automatically detects installed FDDs, but
can determine type unambiguously only for 5.25-inch HD (1.2 MB) FDDs,
which spin at 360 RPM rather than 300. For other drive types, older
machines assume 360 KB or 720 KB and newer systems assume 1.44 MB.
Use BIOS Setup to confirm that the drive type is configured
correctly.
If you add or
replace an FDD, also replace the cable, particularly if it is the
original cable. Manufacturers often fold and crimp the FDD cable for
improved cable routing and airflow. An old cable that has been so
treated is no longer reliable, especially after you disturb it to
install the new drive.
All but the oldest FDD controllers use
line 34 for Change Line Support. When the FDD door is opened, the FDD
signals on line 34 to tell the system that the diskette may have been
changed. If you install a 360 KB or 720 KB FDD, verify the Change
Line setting, ordinarily set on the drive by a jumper labeled
"Line 34" or
"Change Line." If you install such
a drive in a PC/XT-class system, leave the jumper open. On any later
system, install a jumper block to connect line 34 and enable Change
Line Support. Failing to do so and then writing to a diskette in that
drive may destroy the data on that diskette by overwriting the FATs
and root directory entries with data from the diskette that was
formerly in the drive.
FDDs are
used so little nowadaysan occasional boot or program
installthat head wear and media accumulation
aren't problematic. Dust needs to be removed
periodically. You can buy special FDD cleaning kits, but we
don't bother with them. Every few months (or when we
open the case for other reasons) we vacuum out the drive and drench
it down with Zero Residue Cleaner or rubbing alcohol.
Don't. Replace the drive. Modern 3.5-inch drives are
so cheap that it makes no sense to repair one, and they are often
sealed units without repair access anyway. Older 5.25-inch drives
often are repairable, but the cost to do so exceeds the cost of
replacing the drive.
