1. Connectors, Jumpers, and
ENE692
LECTURE 3_1
Connectors, Jumpers, and
Logic Board

2. HDD connectors and jumpers
The number and types of connectors on the hard disk depend on the data interface it uses to connect to the system, the manufacturer of the drive, and any special features that the drive may possess.

3. Data interface connector
IDE/ATA (Integrated Drive Electronics ATA) : A 40-pin rectangular connector. Speed: 8.3 Mbps
SCSI: A 50-pin, 68-pin, or 80-pin D-shaped connector (the same shape used for serial and parallel port connectors). A 50-pin connector means the device is narrow SCSI; 68 pins means wide SCSI; 80 pins means wide SCSI using single connector attachment (SCA). Speed: 320 Mbps
The connectors on hard disk drives are generally in the form of a 2xN rectangular grid of pins (where N is 20, 25, 34 or 40 depending on the interface).
While most current SCSI interface connectors are keyed to prevent incorrect insertion (because they are D-shaped), this is not always the case for other interfaces. For this reason, it is important to make sure that the cable is oriented the correct way before plugging it in. The cable has a red stripe to indicate wire #1 and the hard disk uses markers of one form or another to indicate the matching pin #1
A standard hard disk IDE/ATA data interface connector.

4. IDE/ATA configuration jumpers (1)
Drive Select: Since there can be two drives (master and slave) on the same IDE channel, a jumper is normally used to tell each drive if it should function as a master or slave on the IDE channel. For a single drive on a channel, most manufacturers instruct that the drive be jumpered as master.
Slave Present: Some drives have an additional jumper that is used to tell a drive configured as master that there is also a slave drive on the ATA channel. This is only required for some older drives that do not support standard master/slave IDE channel signaling.
Cable Select: Some configurations use a special cable to determine which drive is master and which is slave, and when this system is used, a cable select jumper is normally enabled.
Size Restriction Jumper: Some larger hard disk drives don't work properly in older PCs that don't have a BIOS program modern enough to recognize them. To get around this, some drives have special jumpers that, when set, will cause them to appear as a smaller size than they really are to the BIOS, for compatibility.
For example, some 2.5 GB hard disks have a jumper that will cause them to appear as a 2.1 GB hard disk to a system that won't support anything over 2.1 GB. These are also sometimes called capacity limitation jumpers and vary from manufacturer to manufacturer. See here for more on this.

5. IDE/ATA configuration jumpers (2)
For example, some 2.5 GB hard disks have a jumper that will cause them to appear as a 2.1 GB hard disk to a system that won't support anything over 2.1 GB. These are also sometimes called capacity limitation jumpers and vary from manufacturer to manufacturer. See here for more on this.
Jumper block for an IDE hard disk. The jumpers are labeled "MA" (master), "SL" (slave) and "CS" (cable select). Other IDE drives will have slightly different jumper configuration or placement.

6. SCSI configuration jumpers (1)
SCSI hard disks have more sophisticated controllers than their IDE/ATA cousins, and as a result typically have many more jumpers that can be set to control their operation.
SCSI Device ID: Every device on a SCSI bus must be uniquely identified for addressing purposes. Narrows SCSI drives will have a set of three jumpers that can be used to assign the disk an ID number from 0 to 7. Wide SCSI drives will have four jumpers to enable ID numbers from 0 to 15. Some systems do not use jumpers to configure SCSI device IDs.
Termination Activate: The devices on the ends of the SCSI bus must terminate the bus for it to function properly. If the hard disk is at the end of the bus, setting this jumper will cause it to terminate the bus for proper operation.
Disable Auto Start: When present, this jumper will tell the drive not to automatically spin up when the power is applied, but instead wait for a start command over the SCSI bus. This is usually done to prevent excessive startup load on the power supply.

7. SCSI configuration jumpers (2)
Delay Auto Start: This jumper tells the drive to start automatically, but wait a predefined number of seconds from when power is applied. It is also used to offset motor startup load on systems with many drives.
Stagger Spin: An "enhanced version" of "Delay Auto Start". When a system with many hard drives has this option set for each unit, the drives stagger their startup time by multiplying a user-defined constant times their SCSI device ID. This ensures no two drives on the same SCSI channel will start up simultaneously.
Narrow/Wide: Some drives have a jumper to control whether they will function in narrow or wide mode.
For example, some 2.5 GB hard disks have a jumper that will cause them to appear as a 2.1 GB hard disk to a system that won't support anything over 2.1 GB. These are also sometimes called capacity limitation jumpers and vary from manufacturer to manufacturer. See here for more on this.

8. SCSI configuration jumpers (3)
.Original image � Quantum Corporation
Option header block signals and functions for the Quantum Atlas 10K SCSI drive
For example, some 2.5 GB hard disks have a jumper that will cause them to appear as a 2.1 GB hard disk to a system that won't support anything over 2.1 GB. These are also sometimes called capacity limitation jumpers and vary from manufacturer to manufacturer. See here for more on this.
Option header block signals and functions for the Quantum Atlas 10K SCSI drive.Original image � Quantum Corporation
Many SCSI drives have additional special features that are enabled through more jumpers. Some drives have replaced some of their jumpers with software commands sent over the SCSI interface. SCSI jumpers are often clustered together into what is called an option block.

9. LED connector
Hard disks use a light-emitting diode or LED to indicate drive activity. The hard disk activity LED is a very useful indicator that generally tells the PC user at a glance when the system is active.
Modern PCs have integrated IDE/ATA controllers built into the chipset on the motherboard, so the LED is usually connected to special pins on the motherboard itself. For systems that use add-in controllers, the LED is connected to the controller, as it was in the days before integrated controllers. Over time, as connecting the LED to the controller has become the standard, most manufacturers have dropped entirely the LED connector on the disk itself on IDE/ATA drives.
Since support for SCSI drives is not present in the vast majority of PC motherboards, they often do still come with an external LED connector.
It was quickly realized that having the disks mounted internally to the case made more sense than using external drive bays, but the LED was still desirable. So a remote LED was mounted to the case and a wire run to a two-pin connector on the hard disk itself. This system worked fine when there was just one hard disk, but became a problem in systems that had two or three hard disks. Eventually, the case LED was made to connect to the hard disk controller instead, to show activity on any of the hard disks that were managed by the controller.

10. HDD Logic board (1)
All modern hard disks are made with an intelligent circuit board integrated into the hard disk unit.
It made sense to move most of the control functions to the drive itself.
The most common interface for PC hard disks is called IDE, which in fact stands for Integrated Drive Electronics. The term really refers to where the control logic is and not the interface itself, and since all hard disks today use integrated electronics, the name does not mean anything any more, despite the fact that everyone continues to use it. The other popular PC hard disk interface today, SCSI, also uses drives that have integrated controllers. The more correct name for the IDE interface is AT Attachment or ATA.
Early hard disks were "dumb", meaning that virtually all of the control logic for controlling the hard disk itself was placed into the controller plugged into the PC.This design meant that it was necessary for controllers to be very generalized; they could not be customized to the particulars of a given disk drive since they had to be able to work with any type.

11. HDD Logic board (2)
Today's hard disks contain logic boards that are in most ways more sophisticated than an entire early PC!
The logic board performs several important functions, and as hard disks become faster and more sophisticated, more functions are added to the logic board.
The logic circuits need to be more powerful, to handle changes like geometry translation, advanced reliability features, more complicated head technologies, faster interfaces, and higher bandwidth data streaming from the disk itself.
The logic board of a Cheetah 10,000 RPM 36
GB hard disk drive. The main interface and
power connectors are on the right-hand side; auxiliary connectors on the bottom and left side.
The bottom of the spindle motor protrudes
through a round hole made for it in the circuit
board.
Early hard disks were "dumb", meaning that virtually all of the control logic for controlling the hard disk itself was placed into the controller plugged into the PC.This design meant that it was necessary for controllers to be very generalized; they could not be customized to the particulars of a given disk drive since they had to be able to work with any type.

12. HDD Form factors (1)
Most hard disks are designed to be installed on the inside of the PC, and are produced in one of a dozen or so standard sizes and shapes. These standards are called hard disk form factors and refer primarily to its external dimensions. The reason for standardizing on form factors is compatibility.
Over the life of the PC there have only been a few different hard disk form factors. Since changing a form factor standard requires coordination from the makers of other components Form factors are generally described by a single metric.
For example, the most common form factors today are “3.5-inch” and “2.5-inch”. These numbers generally refer to the width of the drive, but they can be both vague and misleading They usually were chosen for historical reasons and in typically were based on either the platter size of drives that use the form factor, or the width of drives using that form factor.
Without these standards, hard disks would have to be custom-made to fit different PCs. By agreeing on standards shapes and sizes for hard disks--as well as standard interfaces of course--it is possible for any of the thousands of PC makers to purchase units from any hard disk manufacturer and know that there won't be problems with fit or form during installation.
(such as the makers of system cases) there is resistance in the industry to change the standard sizes unless there is a compelling reason to do so. (For example, when laptop PCs became popular new, smaller drives were created to save space and power, important goals in the world of mobile computing.)
Obviously a single number cannot represent both, and in some cases, it represents neither! For example, 3.5" hard disks are generally 4" wide and use 3.74" platters. (The name in this case comes from the fact that the drives fit in the same space as a 3.5" floppy disk drive!) Much more about the relationship between form factors and platters can be found in the discussion of platter size in the media section. You will also find there a detailed description of the trend towards smaller platters in modern hard disks.

13. HDD Form factors (2)
Without these standards, hard disks would have to be custom-made to fit different PCs. By agreeing on standards shapes and sizes for hard disks--as well as standard interfaces of course--it is possible for any of the thousands of PC makers to purchase units from any hard disk manufacturer and know that there won't be problems with fit or form during installation.
(such as the makers of system cases) there is resistance in the industry to change the standard sizes unless there is a compelling reason to do so. (For example, when laptop PCs became popular new, smaller drives were created to save space and power, important goals in the world of mobile computing.)
Obviously a single number cannot represent both, and in some cases, it represents neither! For example, 3.5" hard disks are generally 4" wide and use 3.74" platters. (The name in this case comes from the fact that the drives fit in the same space as a 3.5" floppy disk drive!) Much more about the relationship between form factors and platters can be found in the discussion of platter size in the media section. You will also find there a detailed description of the trend towards smaller platters in modern hard disks.
The five most popular internal form factors for PC hard disks. Clockwise from the left: 5.25", 3.5", 2.5", PC Card and CompactFlash.

14. External HDD (1)
The vast majority of hard disks are internal, which means they are designed to be mounted inside a PC, and hidden from the user. This is why they have a rather "rough" outside appearance, with the logic board exposed, etc.
Some hard disks are available as external drives, especially ones using the SCSI interface. These really do not differ much from internal drives, except that they include an additional outer plastic shell, a power supply to run the disk, and of course, a larger price tag.
They do offer some advantages over internal drives: more expandability, easier installation, usually better cooling, and also interoperability with other systems that use SCSI.
Since they are external, they do not have to be made in standardized form factors.

15. Image � IBM Corporation
The IBM Travelstar E, an external hard disk using a PC Card interface card.
Image � IBM Corporation
External HDD (2)
External drives have found a new market role of sorts as expansion and backup devices for portable computers.
Many varieties are available using either the parallel port or the PC card interface. In the latter design, the hard disk is in an external enclosure, with an interface cable that runs to a PC card. The card connects to the laptop through a PC card slot. The fact that the hard disk is not constrained by the physical limits of the small PC card slot means it can be made much larger than the small drives available in the PC card form factor, while retaining the portability advantages of the PC card interface.
Image � IBM Corporation
The IBM Travelstar E, an external hard disk using a PC Card interface card.

16. External HDD (3)
Modern hard disks have changed to USB interface for easier connection and being applicable to any other device.

17. HDD Packaging and mounting
Packaging and mounting considerations are vital to any consideration of the reliability of a drive, due to its very sensitive components.
This section includes a look at the exterior of the hard disk, a discussion of how the drive is sealed against contamination from the outside air, and how drives should be oriented for maximum reliability.
The entire hard disk is mounted into a physical enclosure designed to protect it and also keep its internal environment separated from the outside air. This is necessary because of the requirement of keeping the internal environment free of dust and other contamination that could get between the read/write heads and the platters over which they float, and possibly lead to head crashes.

18. Base casting and top cover (1)
The bottom of the disk is often called the base casting.
The drive mechanics are placed into the base casting, and another piece of usually aluminum is placed on top to enclose the heads and platters.
A rubber gasket is placed between the base and cover to ensure a tight seal. On some drives, a metallic tape seal is applied around the perimeter of the drive to fully enclose the drive.
The exact shape of the base and cover can vary significantly from drive to drive.

19. Base casting and top cover (2)
Cover (left) and base casting (right) of a
consumer-grade IDE/ATA hard disk drive.
A recirculating filter is still in place on the
Cover.
The base and cover are attached using a number of small screws, usually around the perimeter of the cover.
Additional screws are also used in the middle of the cover; one to stabilize the spindle motor shaft, and one to secure the axis of the actuator assembly. Normally all of these are Torx screws (star-shaped).

20. Base casting and top cover (3)
The entire contents of the base and cover chamber (including the platters, heads and actuator components) are collectively called the head-disk assembly. We should never open the assembly. If we do, we will quickly contaminate the heads and platters, and eventually ruin the drive.
You will also void the warranty of the drive if you try to open it up.
The logic board is normally mounted on the bottom of the base casting, exposed to the outside. It is separated from the base casting using foam or other cushioning material.
The read/write heads are linked to the logic board with a flexible ribbon cable that runs from the logic board through a gasket and into the hard disk chamber, or a set of pins that goes through a hole in the base casting, mating to a special connector inside the head-disk assembly that connects to the heads.

21. Air circulation and air filtration (1)
Air is an essential component for proper drive operation. Regular hard disks are not totally sealed from the outside air, but they definitely are separated from it, in order to ensure that the dirt and dust of the outside air is kept away from the delicate platters and heads of the drive.
Hard disks are not sealed, because they have to be able to pass air between the inside of the drive and the outside, in order to equalize any air pressure differential that may exist between the two environments. This allows the disk to maintain proper equilibrium when the weather changes.
Small breather holes are built in the cases of many drives, placed there for this purpose. The holes are covered with a breather filter which lets air pass through slowly but not dirt or dust. These filters are placed permanently and do not need to be serviced or replaced.

22. Air circulation and air filtration (2)
Closeup shot of the breather holes in the top of a hard disk case. Part of the breather filter can be seen just under the holes.

23. Air circulation and air filtration (3)
Hard disks also have an internal air flow within their sealed chambers (caused by the rotation of the platters--there is no fan inside a hard disk). This air flow is used to continuously filter the air within the disk assembly.
Despite building the hard disks in ultra-clean facilities and taking other precautions during manufacturing, a small recirculating filter is built into the drive itself as an added security measure.
This filter is designed to work on the air that flows within the hard disk assembly, catching any minute bits of debris that might somehow make it inside. This reduces the chances that such dirt will end up on the disk platters. Like the breather filter, the recirculating filter is not changeable, nor does it need to be.
A recirculating filter in the top cover of a consumer-grade hard disk.

24. Orientation and mounting
Orientation refers to how the hard disk drive is physically installed into the PC. In the majority of cases the drive is installed in the "default" way: flat, with the drive parallel to the ground, the logic board facing down and the drive label facing the sky.
Since hard disks today are much more solidly built, and they use voice coil actuators for dynamic head positioning. They can be side-mounted in the case without any problems, and can also have its orientation changed after it has been in use for some time.
Mounting holes on a SCSI hard disk,
viewed from the bottom of the drive. The one at left is part of the set of
holes used if putting the mounting screws into the bottom of the drive;
the one at right is for side mounting.
Some PC cases, however, especially the smaller desktop boxes, have side-mounted hard disk bays. Either of these orientations is common and should present no problems. In fact, most manufacturers say that you can mount their drives any way you wish, even upside-down if it is necessary. That said, my personal opinion--one shared by at least one manufacturer--is that you should avoid strange mounting positions if it all possible. The reason is simple: most testing of drives is done with them in either of the standard orientations. Hard drive manufacturers don't do nearly as much testing of drives mounted upside-down as they do of drives right-side up. For the sake of reliability, it's best to keep things simple if at all possible, and well, go with the flow.

25. Temperature limits and drive cooling (1)
The faster drives, with their faster more powerful spindle motors, generated more heat than had been seen before in hard disks. In fact, heat issues are common with each first-generation drive family using a newer, faster spindle speed.
When trying to keep a hot drive within operating parameters, the most important first step is to address the cooling of the case overall. It's essential that the fan(s) are functioning properly and have sufficient capacity for the case.
The PC must not be operated in a very hot room or placed where it will be excessively heated.
The case should not be too small for the number of devices it contains.
Hard drives should also be spaced to allow proper air flow over them--putting two drives very close together is not a good idea.

26. Temperature limits and drive cooling (2)
Drive Coolers: These are essentially fan and heat sink combos, similar to those used for CPUs, but designed specially to be used with hard disks. They are attached to the drive using thermal conductive tape, and blow air directly onto the drive case to cool it.
Original image � PC Power & Cooling, Inc.
A drive cooler mounted on top of a standard 3.5“ form factor hard disk.
The power plug is visible at right.

27. Temperature limits and drive cooling (3)
Bay Coolers: These devices are similar in design to the drive bay adapters available for mounting a 3.5" form factor drive into a 5.25” drive bay, except that they add cooling for the drive. The disk is mounted into the cooler, which contains one or more integrated fans. The cooler then is mounted into one of the larger 5.25” drive bays found in most PCs.
A 5.25” bay cooler with a 3.5” form
factor hard disk installed in it. This view is
from the inside of the case; the external
faceplate is at rear.
Original image � PC Power & Cooling, Inc.
In both designs power is provided for the fan(s) through the use of a standard
drive connector.

28. Do you need active cooling for your hard disk?
It depends on a number of different factors. Most PC users do not need to add special coolers for their hard disks. This is especially true of consumer IDE/ATA drives--since manufacturers know most people pay little attention to cooling, they must assume no special cooling when selling these drives through retail channels, or they would end up having to deal with a flood of warranty replacements.
For higher-speed SCSI drives, additional cooling may be required. You will have to determine the need by assessing the cooling level of your system, the temperature requirements and heat generation level of the particular drive, how many drives are going to be put into the system, and similar factors.

29. Retail and OEM packaging
Most hard disk drive models are sold as two different packages: OEM drives and retail drives (sometimes called retail kits). Retail drives are drives that are distributed to retail stores and online dealers for sale to the general public.
OEM drives are those sold to system manufacturers in large quantity, for inclusion in PCs built for resale: "OEM" stands for "original equipment manufacturer" and refers to a company that makes PCs (or other equipment).

30. What comes in retail packaging?
Hard Disk Drive: The hard disk drive itself, in an anti-static bag or similar package.
Installation Instructions: Instructions on how to configure and install the hard disk.
Drivers and/or Overlay Software: A floppy disk or CD-ROM containing any necessary drivers or utilities, and usually, a copy of that manufacturer's version of drive overlay software for working around BIOS capacity problems in older systems.
Mounting Hardware: A set of appropriately-sized screws for mounting the drive into the system case.
Interface Cable: A cable of the correct type for the drive's interface.
Warranty Card: A card describing the warranty provided on the drive, usually three or five years in length.
Pretty Box: A very colorful box that looks nifty and holds all of the above.

31. What comes in OEM packaging?
Hard Disk Drive: The hard disk drive itself, in an anti-static bag or similar package.
Jumpers: One ore more jumpers needed for configuring the drive.
The reason that OEM packaging is so "plain" is that most OEMs do not need the additional support materials and packaging required for a proper retail package--they are just going to put the drives into PCs, not resell them to end users.
OEM drives began to appear for sale to individuals and end-users. Many experienced PC home-builders and upgraders realized they do not need most or even all of the goodies in a retail package, and preferred the lower price of the OEM drives.

32. HDD handling
Hard disks are very delicate and sensitive instruments. All hard disk drives have to be properly handled to avoid damage. In most cases, handling of drives is something that happens very little anyway: you get the drive, you install it and you leave it there.
Hard disks are always transported in an anti-static bag. This is of course to prevent the damage that can occur to the hard disk's circuits as a result of electrostatic discharge or ESD.

33. Seagate’s Seashell bag
Seagate has actually come up with a neat improvement on the standard anti-static bag called SeaShell.
It is a solid plastic clam-shell case that not only provides ESD protection for the drive, but physically protects it against shock as well.
These little cases are both recyclable and easily reusable.
A Seagate "SeaShell", containing a Cheetah SCSI drive.
Original image � Seagate Technology

34. ESD safety precautions
Be sure to ground yourself to a metal object before removing a hard disk from its ESD protection.
Handle the drive as little as possible, and avoid bumping or jarring it if at all possible. The safest thing to do is to simply get it installed as quickly as possible.
Since the logic board on internal drives is exposed, make sure none of its components contact anything metallic that could cause a short or a static discharge.
When shipping a hard disk drive, it is essential that you properly package it.. The drive should be properly supported on all sides with solid foam or other similar padding, and fitted properly in a box of the correct dimensions.