Brooklyn Technical High School



Student Version L E S S O N P L A N #24 Per. Name:

CLASS: Computer Repair, Maintenance, Upgrade and Management DATE: Monday November 9th, 2009

TOPIC: Hard Drives AIM: What is the geometry of a Hard Disk?

NOTE:

Do not change any settings on the computer. Keep your computer area clean. Don’t write on the computers. Don’t throw your garbage underneath your desks.

H.W. # 24:

1) What is the purpose of the platters in a hard drive?

2) How is data stored on hard drives?

3) How is a platter divided up so that data can be written to it?

4) What is Zoned Bit Recording?

5) How does the old AT BIOS for hard drives arrive at a maximum HD capacity of 504MB?

6) What were the different modes or standards developed for transferring data from the Hard Drive to Memory?

DO NOW: Go to and look up how IDE controllers work. Read through the pages to see how hard drives work to prepare you for today’s lesson.

PROCEDURE:

Write the AIM and DO NOW.

Get students working!

Take attendance.

Go Over HW

Collect HW

Go over the Do Now

Hard drives have come and have come in different sizes. Previous hard drives came in the 5.25” form factor. Most hard drives come in 3.5” form factor, except for notebook hard drives that come in the 2.5” form factor.

|Platter Diameter |Typical Form Factor |Application |

|5.12 |5.25" |Oldest PCs, used in servers through the mid-1990s and some retail drives|

| | |in the mid-to-late 1990s; now obsolete |

|3.74 |3.5" |Standard platter size for the most common hard disk drives used in PCs |

|3.0 |3.5" |High-end 10,000 RPM drives |

|2.5 |2.5", 3.5" |Laptop drives (2.5" form factor); 15,000 RPM drives (3.5" form factor) |

|1.8 |PC Card (PCMCIA) |PC Card (PCMCIA) drives for laptops |

|1.3 |PC Card (PCMCIA) |Originally used on hand-held PCs (no longer made) |

|1.0 |CompactFlash |Digital cameras, hand-held PCs and other consumer electronic devices |

Let’s take a look at what is inside the hard drive casing.

• Platters – consist of an aluminum alloy material for support with a magnetic material over it that actually stores the data. Each platter can have data recorded on both sides. Each side of a platter is broken up into tracks, and the individual tracks broken up into sectors.

• Tracks - All the platters are broken up into tracks. The tracks are numbered starting from 0 on the outside and counting up as you go in

• Sectors – Each track is broken up into sectors. Each sector holds 512 bytes of user data

• Cylinders – When referring to hard disks, we usually use the term cylinders instead of tracks. The reason is that as the actuator arm moves the head to a particular track all the heads on the other platters move to the same track. So in essence the head is moving across the cylinder (a cylinder is like a stack of circles of height h).

• Zoned bit recording – This places more sectors on the outer track to conserve space

Before ZBR, a hard disk would have to space out its data once it got to the outer tracks. The cylinder where it started getting wider was known as the Write Precomposition Cylinder. We also had to enter this value in CMOS. But this isn’t used anymore because of ZBR.

The other thing we used to have to enter in CMOS was the landing zone when the hard drive stopped spinning. But because of the voice coils parking themselves, we don’t need this anymore.

In these old days, IBM developed preset combination of hard drive geometries and called these hard drive types. For example, here are two types

|Drive Type |Capacity (MB) |Cylinders |Heads |Sectors |Write Precomp |Landing Zone |

|1 |10 |306 |4 |17 |128 |305 |

|45 |116 |1314 |7 |26 |None |1314 |

Today’s hard drives have the CHS values stored on them and when your computer starts up, BIOS queries the hard disk. The hard disk sends the BIOS its CHS geometry, so now the BIOS knows the hard drive’s CHS information.

• Read Write Heads – Actually read data from and write data to the platters. There will be two heads per platter since data is being written to both sides of the platter. Initially the heads rest on the platter. Once the platter starts spinning the head lifts off the platter and floats above the platter. But the space is very small, so as a result, hard drive casings are sealed with a filter so that no particles enter the casing. The heads read and write data using an encoding scheme. The most current one is RLL (run length limited). The older ones were MFM (modified frequency modulation) and FM (frequency modulation). If necessary discuss flux reversal and how FM works (if there is a change the bit changes from what it was before.

|Spindle Speed (RPM) |Average Latency (Half |Typical Current Applications |

| |Rotation) (ms) | |

|3,600 |8.3 |Former standard, now obsolete |

|4,200 |7.1 |Laptops |

|4,500 |6.7 |IBM Microdrive, laptops |

|4,900 |6.1 |Laptops |

|5,200 |5.8 |Obsolete |

|5,400 |5.6 |Low-end  IDE/ATA, laptops |

|7,200 |4.2 |High-end IDE/ATA, Low-end SCSI |

|10,000 |3.0 |High-end SCSI |

|12,000 |2.5 |High-end SCSI |

|15,000 |2.0 |Top-of-the-line SCSI |

• Actuator arms. The heads are connected to an actuator arm that moves the head around to a particular location on the hard disk. The first hard disks used stepper motor technology for the actuator arms. This technology moved the arms in fixed increments (With these old programs you had use a program to park the arm at an unused location. After a while it became necessary for the actuator arm to move more precisely so they now hard drives used a voice coil to give more precise movements.

• Spindle motor – The spindle motor spins the platters at speeds ranging from 3600 rpm to 15000 rpm.

Now to the outside of the drive:

Hard Drive Interfaces or standards for connecting hard drives to motherboards:

At right you see the bottom of the hard drive which contains the controller board filled with ROM programming to instruct the read/write heads how, where and when to move across the platters and write and read data.

We’ll see different standards such as Parallel ATA, serial ATA, SCSI and others. We’ll first focus on Parallel ATA drives

A little history: With the first hard drives, you always had to do a low-level format, i.e. break up the platters into tracks and sectors. You had to type in all the CHS information about the drive into the BIOS. There always was a controller card that controlled the drive and you had to connect your drive to the controller card.

Western Digital and Compaq developed a new hard drive interface and placed this specification before ANSI (American National Standards Institute). ANSI put out the AT Attachment interface or ATA, which required a new 40-pin 40 wire ribbon cable and a built-in controller card on the drive itself. This eliminated the need for a low level format. The name that is more commonly used for ATA drives is IDE (Integrated Drive Electronics). Later Parallel ATA drives use a 40-pin 80-wire ribbon cable to accommodate the higher transfer speeds.

The hard drive connects to the motherboard via what is known as an IDE interface. On a motherboard you will usually find connections for two IDE drives or drives that meet the ATA standard for connections.

Western digital proposed improvements to the IDE standard and called the new standard EIDE. (EIDE includes support for higher capacity drives, support for non-hard drive storage devices, support for two more ATA devices for a maximum of 4, and improved throughput). IDE drives disappeared. But we still usually call EIDE drives IDE.

When the computer boots up, BIOS will look for one IDE interface first. That is the primary controller. The other controller is the secondary controller. Each controller can connect up to two devices. Because two different devices connect to the same controller, there has to be a way to differentiate (no twists in the wires like in a floppy drive cable). The EIDE standard identifies one device as master and another as slave as indicated by the jumpers on the drives (case in point, I had a machine with a hard drive on IDE1 and the DVD-ROM drive on IDE 2, both as masters for their respective controllers. When I got a CD Recorder, I put the recorder on IDE 2 as the master and the DVD-ROM on IDE 2 as the slave. I left my hard drive as master/single on IDE 1

|Cable Select |

|A feature of some PCs that allows IDE/ATA hard disks to be numerically identified by the order in|

|which they are attached to the cable. Both the BIOS and the drive must support this feature. |

|Without Cable Select, jumpers on the IDE drive must be set to Master or Slave designations |

Hard Drive Size Limitations:

When IBM first made their PCs, they created the AT BIOS to support hard drives. The AT BIOS was a set of commands that was used to allow the hard drive to communicate with the PC. When IDE drives came out, the developers of IDE wanted to make sure their drives were compatible with the AT BIOS command set. BIOS routines for the original AT command set limited the hard drive capacity to 504MB. At the time, the biggest hard drive was only 10MB, so it seemed 504MB wouldn’t be reached.

With standard IDE drives, the limit for capacity was 1024 cylinders, 16 heads, and 63 sectors per track (one of the sector values (0) was unusable). Multiplying 512 bytes per sector by 63 sectors per track by 16 heads by 1024 cylinders gave us the 504MB limit.

During this time, hard drive manufacturers were able to make drives with fewer heads but many more cylinders; much more than the 1024 limit. To be able to overcome this limit, hard drives had an actual physical geometry, and a logical geometry that was reported to the CMOS. As an example, take into account the actual geometry of a drive that has 2,048 cylinders, 2 heads and 52 sectors per track (what is the capacity?). A problem with this setup as it relates to the old AT BIOS for hard drives, is that the number of actual cylinders surpasses the 1024 cylinder limit of the AT BIOS. So the hard drive did some sector translation to make it appear to the BIOS that the hard drive geometry is still within the AT BIOS limits. A sector translation for an actual geometry of 2,048 cylinders, 2 heads and 52 would be a logical geometry of 512 cylinders, 8 heads, and 52 sectors per track

To accommodate the increasing size of hard drives, a method called Logical Block Addressing (LBA) was devised. LBA took advantage of unused commands to use up to 256 heads, instead of 16 heads. This allowed for a maximum of 8.4GB hard drives.

By the mid 1990’s it was obvious that 8.4GB was not going to cut it. We needed a new method of overcoming the 8.4GB limit. In 1994, Phoenix Technologies (A BIOS manufacturer) came up with a new set of BIOS commands called Interrupt 13 extensions. A system with INT 13 extensions can handle drives up to 137GBs. Most systems since 1998 have INT 13 extensions support. If you install a hard drive larger than 8.4 GB and AutoDetect does not detect more than 8.4 GB, your system does not support INT 13 extensions.

Hard drive size exploded just after the 21st century began. When drives started hitting the 120GB mark, the ANSI ATA committee adopted an industry proposal from Maxtor (A major hard drive maker) called Big Drives that increased the limit to more than 144 petabytes (144,000,000 GB). The ANSI ATA committee called this new standard ATA/ATAPI-6.

Data Transfer from Hard Drive to Memory:

The older way of transferring data from the hard drive to memory was called Programmed Input/Output mode. This is a technique whereby the system CPU and support hardware directly control the transfer of data between the system and the hard disk. There were several speeds of Programmed Input/Output, which were called PIO modes. When you got your hard drive, you had to go into CMOS and tell CMOS what was your PIO mode, unless your CMOS had an auto detect option for PIO mode. The 5 PIO modes were

|PIO Mode |Cycle Time (nanoseconds) |Maximum Transfer Rate |Defining Standard |

| | |(MB/s) | |

|Mode 0 |600 |3.3 |ATA |

|Mode 1 |383 |5.2 |ATA |

|Mode 2 |240 |8.3 |ATA |

|Mode 3 |180 |11.1 |ATA-2 |

| Mode 4 |120 |16.7 |ATA-2 |

The PIO method of transferring data had a serious flaw; it required the care and attention of the system’s CPU. Clearly, a better solution is to take the CPU out of the picture entirely, and have the hard disk and system memory communicate directly. This was done using DMA (Direct Memory Access).

Here are the early DMA modes of transferring data from hard drive to memory

|DMA Mode |Cycle Time |Maximum Transfer Rate |Defining Standard |

| |(nanoseconds) |(MB/s) | |

|Single Word Mode 0 |960 |2.1 |ATA |

|Single Word Mode 1 |480 |4.2 |ATA |

|Single Word Mode 2 |240 |8.3 |ATA |

|DMA Mode |Cycle Time |Maximum Transfer Rate |Defining Standard |

| |(nanoseconds) |(MB/s) | |

|Multiword |480 |4.2 |ATA |

|Mode 0 | | | |

|Multiword |150 |13.3 |ATA-2 |

|Mode 1 | | | |

|Multiword |120 |16.7 |ATA |

|Mode 2 | | | |

|Ultra DMA |Cycle Time |Maximum Transfer Rate |Defining Standard |

|Mode |(nanoseconds) |(MB/s) | |

|Mode 0 |240 |16.7 |ATA/ATAPI-4 |

|Mode 1 |160 |25.0 |ATA/ATAPI-4 |

|Mode 2 |120 |33.3 |ATA/ATAPI-4 |

|Mode 3 |90 |44.4 |ATA/ATAPI-5 |

|Mode 4 |60 |66.7 |ATA/ATAPI-5 |

|Mode 5 |40 |100.0 |ATA/ATAPI-6? |

|Mode 6 | |133 | |

To use Ultra DMA modes over Mode 2, a special, 80-conductor IDE cable is required. This cable uses the same 40 pins as the old cables, but adds 40 ground lines between the original 40 signals to separate those lines from each other and prevent interference and data corruption

Sample Test Questions:

1) What is a type of IDE translation?

A) LBA B) UTB C) QIC D) USB

2) Assuming that both the primary and secondary IDE controllers are enabled, what is the maximum number of IDE devices that can be connected?

A) 3 B) 4 C) 5 D) 6

3) How many pins does a standard IDE controller have?

A) 34 B) 36 C) 40 D) 50 E) 68

4) On a system with one hard drive and one CD-ROM drive, what is the typical placement of the CD-ROM drive?

A) Slave on the primary IDE channel B) Master on the primary IDE channel

C) Slave drive on the secondary IDE channel D) Master drive on the secondary IDE channel

5) You just installed a new IDE hard drive, but your system BIOS will not recognize the new drive. Of the following, what should you check first?

A) Cable sequence B) Jumpers on the hard drive C) Drivers that need to be loaded

D) Hard drive manufacturer website information

6) Which step must you complete when installing a second IDE drive on the same IDE controller that has an existing device?

A) Set the drive identification to match

B) Terminate the second drive properly

C) Set one drive to master and the other to slave

D) Place the boot drive at the end of the IDE cable

7) You have installed a new CD-ROM drive on the secondary IDE controller with an existing IDE on the secondary IDE controller. Now neither device works. What should you do?

A) Install new CD-ROM Drive drivers

B) Check Master/Slave jumpers

C) Plug in the CD-ROM drive power cable

D) Delete the drivers for the existing storage device

8) You have an older PC that has only 1 IDE controller/interface. One IDE hard drive and one IDE CD-ROM drive are also installed on the PC. How should you add a second IDE hard drive?

A) Install a SCSI card B) Install an add-on IDE interface card

C) Use an IDE cable that has extra connections on it

D) Use the existing free connector on the floppy drive cable

9) Which settings determine which IDE device is a master and which IDE device is a slave?

A) Hardware settings on the device B) Hardware settings on the motherboard

C) Software settings on the operating system D) Hardware settings on the IDE controller board

10) How many devices can connect on a single IDE channel?

A) 1 B) 2 C) 3 D) 4

11) What can be done with a system when its IDE controller fails on the motherboard?

A) Install a new driver B) Reset the ROM BIOS

C) Replace the hard drive D) Install an IDE add-on card

12) John’s system is running INT 13 extensions. What is the maximum hard drive size it can support?

13) Which are the 3 important geometries of the hard drive?

14) How many IDE hard drives can you have on a system with two IDE hard drive controllers?

15) How do you differentiate two IDE drives on the same cable?

16) What happens if you cable an IDE drive incorrectly?

17) What was the maximum hard drive size that the BIOS routines for an original AT command set enabled?

18) John has just purchased an ATA/66 capable hard drive for his ATA/66-capable system. However, he notices that he forgot to get the special 80-wire cable? If he installs the ATA/66 drive with a 40 wire 40 pin IDE cable, what will happen?

19) A ________ provides enough power to perform an orderly shutdown during a blackout.

20) What determines the type of case that a motherboard needs and provides the maximum expansion slot limit?

21) AT motherboards used a connector called a ________ to put the physical ports on the back of the case (since the only onboard connector for the back was the DIN connector.

22) The LPX and NLX form factors provide an insertion slot for the ________ card.

Sample Test Questions:

1) What is the term for one of the segments of a track on the platter of a magnetic disk?

A) Cluster B) Sector C) Cylinder D) Allocation Unit

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Ultra DMA means that transfers occur on both the rise and fall of the clock signal. Like Dual Data Rate (DDR RAM)

Multiword means that several 2 bytes chunks of data were sent at a time.

Single word means 2 bytes at a time.

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