ENE692
LECTURE 3_1
Connectors, Jumpers, and
Logic Board
1
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.
2
http://www.storagereview.com/guide2000/ref/hdd/op/act.html
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
A standard hard disk IDE/ATA data interface connector.
• 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).
http://www.storagereview.com/guide2000/ref/hdd/op/jumpPower.html
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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.
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IDE/ATA configuration jumpers (2)
• 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.
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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.
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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.
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SCSI configuration jumpers (3)
.Original image � Quantum Corporation
Option header block signals and functions for the Quantum Atlas 10K SCSI drive
•
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.
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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.
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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.
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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.
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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.
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HDD Form factors (2)
•
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.
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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.
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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.
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External HDD (3)
• Modern hard disks have changed to USB interface for easier connection and
being applicable to any other device.
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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.
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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.
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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).
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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).
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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.
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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.
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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.
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Seagate’s Seashell bag
• Seagate has actually come up with a neat improvement on the standard antistatic 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
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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.
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