Flash and Removable Storage - Upgrading and Repairing PCs - page 639

chip and therefore don't have a built-in floppy controller. Such systems can still use a
floppy drive, generally in the form of an external USB drive.
Although traditional floppy controller cards and multi I/O cards have provisions for two
floppy drives (A: and B:), most motherboards with integrated floppy controllers support
only a single drive.
Power and Data Connectors
External USB floppy drives use the USB connector for power and data. However, nearly
all internal floppy disk drives have two connectors—one for power to run the drive and
the other to carry the control and data signals to and from the drive. These connectors
are fairly standardized in the computer industry. A 4-pin inline connector (called Mate-N-
LockbyAMP)inbothlarge(Molex)andsmall(Berg)stylesisusedforpower(see Figure
18.29 ) , and a 34-pin connector in both edge and pin header designs is used for the data
and control signals. Typically, 5 1/4-inch drives use the large-style power connector (the
same as used by ATA hard disks and optical drives) and the 34-pin edge-type connector,
whereas most 3 1/2-inch drives use the smaller version of the power connector and the
34-pin header-type logic connector.
BoththeMolexandBergpowerconnectorsfromthepowersupplyarefemaleplugs.They
plugintothemaleportion,whichisattachedtothedriveitself.Notethatthepin-to-signal
designations on the small connector are the opposite of those on the large connector.
One common problem with installing 3 1/2-inch drives in some systems is that the
power supply might not have an available small-style (Berg) power connector used by
the smaller drives. An adapter cable that converts the Molex peripheral power connect-
or to the proper Berg connector used on most 3 1/2-inch drives is available from Dalco
( www.dalco.com ) under P/N 47425 and from other sources. You can also use a splitter
that converts aMolex connector into oneeach, BergandMolex (Dalco P/N43435),orin-
totwoBergconnectors(DalcoP/N51075).Splittersarealsoavailablefromothersources.
The Floppy Disk Controller Cable
The 34-pin connector on an internal floppy disk drive takes the form of either an edge
connector (on51/4-inch drives) orapinconnector (on31/2-inch drives). The pinouts for
the floppy controller connector are shown in Table 10.5 .
Table 10.5 Floppy Disk Drive Controller Connector Pinout