UPGRADING REPAIRING PCs

Pin 1 (Colored Wire)
Motherboard Connector
Pin 34
3.5" Drive “B” Connector
Figure 5.4 Standard five-connector floppy interface cable.
Floppy Drives 147
5.25" Drive “B” Connector
Table 5.1 Comparing Ribbon Cables—Floppy Versus Hard Disk
Interface
Type Floppy ST-506 ESDI IDE SCSI
Cable 34-pin 34-pin 40-pin or 50-pin or
Width 80-strand 68-pin
Notes Almost all have Can be straight 80-strand cable
twist between A: or twisted; twist has 40 pins;
drive connectors away from pin 1; designed for
and B: drive obsolete and use with
connectors; twist seldom seen UDMA/66
toward pin 1 today; used motherboards
(colored edge with 20-pin and drives
of cable) ribbon cable
Table 5.2 lists the parameters for current and obsolete disk drives
used on PCs. If you are preparing a drive with FORMAT that is
smaller than the drive’s capacity, you will need to set the FORMAT
parameters manually.
A damaged media descriptor byte will prevent programs from properly
accessing the disk; however, this problem can be fixed with
Norton Utilities.
Table 5.2 Floppy Disk Logical Formatted Parameters
Current Formats Obsolete Formats
Disk Size
(inches)
3 1/2 3 1/2 3 1/2 5 1/4 5 1/4 5 1/4 5 1/4 51/4
Disk Capacity
(KB)
2,880 1,440 720 1,200 360 320 180 160
Media
Descriptor
Byte
F0h F0h F9h F9h FDh FFh FCh Feh
Sides (Heads) 2 2 2 2 2 2 1 1
“Twist”
3.5" Drive “A”
Connector
5.25" Drive “A”
Connector