Mounting the Floppy Drive

Now you should mount the drives into the case. The floppy drive should go into one of the smaller (3 1/2") bays.



Make sure that it is flush with the front of the case, and then put the screws in. While it is always better to mount the drives with four screws, only two are really needed. If you are only going to use two screws, make sure that they go in opposite corners (left front/right rear or right front/left rear).



Next, you have to connect the floppy cable. The floppy cable will be the one that has a weird twist in it.



One of the wires should have red dots on it (on the left, in the above picture). The red dots indicate with side of the cable should line up with "pin 1" on the motherboard and on the drive.

Locate pin 1 on the floppy controller on the motherboard. If you can't figure out which one is the floppy controller, just compare the size of the floppy cable connector with the different sockets on the motherboard - the floppy cable will only fit into one of those sockets. In the below pictures, the floppy controller is the bottom one. Note that the IDE controllers have sockets that are longer than the floppy controller's. You may have to consult the manual for your motherboard if you can't figure out which one pin 1 is. If you are looking at the socket, and the notch in the socket is on the bottom, then pin 1 will be on the left side. The bottom picture show a close up of the same connectors after cables have been hooked up. Note that on the lower left side of each IDE socket is a printed "1" indicating which pin is pin1 (it's kind of hard to see, but they're circled in green). Also note that the red side of the cables correspond with the pin 1's.





Sometimes, the motherboard will actually have "Pin 1" labelled on it.



Then connect the floppy cable to the drive itself. The end that you connect to the drive should be the one that has the twist in it. When you power up the computer, if the light on the front of the floppy drive comes on and stays on, then you have connected this cable incorrectly. The light on the front of the floppy drive should come on briefly and then go off. If the light does not come on at all, then you either have a defective drive, or you have forgotten to hook up one of the cables.



Finally, connect the power cable to the floppy drive. The floppy power connector will be smaller than the rest of the power connectors. Make sure that the power cable lines up with the pins on the back of the floppy drive. This typically involves a lot of force to connect. And they are usually very difficult to disconnect. So, before connecting it, make sure that it's where it's supposed to be. Note that in the below pictures, pin 1 on the drive itself is denoted by a triangle that has been stamped into the drive, just below and on the left side of the floppy connector.

Floppy Drive Alignment Test Parameters

The read/write heads of the drive must have three basic alignment parameters checked and maintained:

1. Radial head alignment determines the exact position of the drive's read/write head over a given track location. As discussed above, this parameter is by far the most critical and most common alignment problem. For instance, a standard 3.5 inch drive with its read/write head displaced from the nominal standard more than +/- 600 millionths of an inch, would be considered out of specification. This drive would probably have difficulty reading a diskette written on another drive, especially if the other drive was misaligned in the opposite direction.

   
   

2. Azimuth head alignment is the angle, in fractions of a degree (minutes), of the read/write head on its vertical axis. Like the radial parameter, azimuth is very critical for reliable data exchange between drives, but the incidence of occurrence of a read/write head with incorrect azimuth causing an interchange problem is somewhat less. This is because the drive's head positioner mechanism routinely moves the heads radially going from track to track, however the azimuth alignment is fixed at the factory and should never change unless the drive is damaged or worn badly. Like the radial parameter, if the read/write head has poor azimuth then it may have difficulty reading a diskette that was written on a drive with a proper azimuth angle, or worse yet a drive with its azimuth angle incorrectly adjusted in the opposite direction from nominal.

   

3. Index timing head alignment relates to the starting point on each track where data is stored. The starting point is determined by the placement of an index sensor on the drive which triggers once with each revolution of the diskette and serves as the reference point. Should this sensor be out of adjustment, then the starting point of the data written to the diskette will be altered. Fortunately, most modern soft sectored disk formats used with personal computers today don't rely heavily on this parameter being perfectly adjusted. Therefore it is seldom a serious problem unless severely out of adjustment or the index sensor has failed completely.

   

Beyond just the read/write heads, there are other parameters to be adjusted and maintained within the drive which also are commonly referred to as "alignment":

1. Head Positioner Linearity. This is the ability of the drive's head positioner mechanism to maintain the radial alignment of the read/write heads to be constant throughout all of the available tracks on the diskette. Since the track spacing of the recorded tracks should be constant across the entire surface of the diskette (96 tracks per inch in the case of the HD 5-1/4" for example), it is very important that the drive being used to store data or programs be able to maintain its radial alignment very precisely across this entire area. A defective drive might have perfect radial alignment at one track location, but exhibit considerable error at another area of the diskette's surface, which will cause a failure when read by another drive which has no linearity problem.
   
   
2. Motor Spindle Eccentricity. This is defined as the wobble that a diskette may have as it spins in the drive. Ideally, the diskette should rotate in the drive such that the invisible tracks are a fixed distance from the center of the diskette during the entire rotation. When a drive has an eccentricity problem, this results in radial alignment which varies as the diskette turns each revolution. If this happens, some recorded sectors might have good radial alignment, while others are off-track. This will result in failures very similar to a radial alignment problem except that some sectors of a given track may be readable while others will fail.
   
   
3. Track 0 Sensor Adjustment. This is the physical adjustment of the drive's track 0 sensor. In most drives, this is an optical sensor which must be adjusted such that when the system is first powered on, or recalibrated, (ie, blindly sent to track 0 by the controller), the drive's heads are able to be placed accurately at the starting track 0. The computer's floppy controller relies on this sensor to establish a starting point from which all other tracks are referenced.
   
   
4. Index Timing. Index timing is a standardized fixed angular location between the drive's index sensor which triggers with each revolution of the diskette, and the read/write heads. Once the two heads are adjusted to have very close to the same angular location relative to each other, then relative time between the index sensor and the read/write heads must be set. This is usually a straightforward physical adjustment of the drive's Index sensor, to bring it to within specification.
   
   
5. Index Skew. This is the drive's ability to maintain the index timing to be constant along the complete travel of the read/write heads in order to access all of the tracks recorded on the diskette. If the Index timing is good at track 0, but out of specification at the innermost track, then the drive would be said to have unacceptable index skew. This is not a flaw in the read/write heads, but rather a misalignment of the head positioning mechanism, which is not able to move on the correct line as it should. If the mechanism was out of line enough, it could also have a significant effect on the head's azimuth, which would change from track to track as the heads traveled more and more out of line due to the mechanism being skewed.
   
   
6. Motor Spindle Speed. This parameter simply indicates how fast the drive is spinning the diskette. It is usually expressed in revolutions per minute or sometimes in milliseconds per revolution. The drive should be able to spin the diskette at a correct and constant speed. If the drive spins the diskette too slowly, the recorded data will arrive at the floppy controller at a frequency which is too low. If the drive spins too fast, the frequency will be too high and when writing information, the controller will not have enough time within the time frame of one revolution of the diskette to record the necessary data fields for reliable operation.

Floppy Drive

Floppy disk drives were originally introduced commercially as a read-only device to hold microcode and diagnostics for large IBM mainframe computer systems in the early 1970s. By changing the diskette inside the floppy drive, service engineers could easily update the microcode to the latest revisions or load diagnostics in an easy and timely manner. These first commercial floppy drives were physically quite large and used 8 inch diskettes recorded on only one side.



The storage capacity of these early read-only drives was less than 100 kilobytes. In 1973 a new upgraded 8 inch drive with read/write capability and a capacity of about 250 kilobytes began shipping which IBM used in data entry systems. This drive incorporated many technical improvements and became somewhat of a model for drives still in use today. As time went on, designers learned how to reliably record on both sides of the diskette as well as increase the density of the data recorded on the diskette.



In 1976 floppy drives were introduced in the 5.25 inch size by Shugart Associates. In a cooperative effort, Dysan Corporation manufactured the matching 5.25 inch diskettes. Originally these drives were available in only a single-sided low density format, and like the first 8 inch models, stored less than 100 kilobytes. Later they received many of the same enhancements made to the 8 inch models, and eventually 5.25 inch floppy drives settled at a double-sided, "double density" formatted capacity of about 1.2 megabytes. This drive was used in the IBM 'AT' personal computer. It is also the popular 5.25 inch model still with us today.



Modern floppy drives and diskettes have evolved to a much smaller size with larger capacities as well. In 1980, the 3.5 inch floppy drive and diskette was introduced by Sony. During the early 1980's many competing formats were tried to compete with the 3.5 inch drives. From various companies there were 2.0, 2.5, 2.8, 3.0, 3.25, and 4.0 inch formats! Fortunately for us, over time the industry settled on the 3.5 inch format which is now standardized and manufactured by many companies. Today's standard 3.5 inch diskettes hold a formatted capacity of about 1.5 megabytes while still using the same basic technology of the second generation 8 inch drives.



Although technology has not changed substantially, floppy drives have certainly changed considerably in order to meet the very demanding needs of the marketplace. The primary factor which caused designers to reduce the size and cost of floppies was the introduction and evolution of the personal computer. It was in the personal computer market that the low cost, mass produced floppy drive found its first real home. Very quickly the floppy became the standard method of exchanging data between personal computers.



It also became the popular method of storing moderate amounts of information outside of the computer's hard drive. Diskettes are small, inexpensive, readily available, easy to store, and have a good shelf life if stored properly.



This article is a discussion of common conventional floppy drives found in today's personal computers. It is important to note that since the early 1980s through the present, high capacity floppy drives have also been introduced to the marketplace. These have come in all three of the popular sizes previously mentioned. Some have achieved data storage capacities and even access times similar to that of small hard drives. Several of these products have come and gone as have some of the companies which produced them.



A few designs continue to be popular to this day, especially for certain applications requiring removability but at the same time more storage capacity than the inexpensive common floppy drives can provide. Because of their inherent higher price, few of these high capacity drives have found their way into the mass produced personal computer. These drives are often sold as an add-on (or add-in) accessory for those who need them.