Controllers and interfaces

1
Controllers and interfaces

• Controller
• Is the adapter board that
• plugs into your PCs
• expansion slot.
• Interface
• Is the communications
• standard that defines how
• data flows to and from the
• disk drive.

2
PC drive interfaces

• SCSI- The Small Computer System Interface is a
  parallel system bus, in some ways like an
  expansion bus. Common use for optical drives.
  Introduced in the early 1980s.
• IDE-The Integrated Drive Electronics (IDE)
  interface is officially known and sometimes
  called the AT attachment or ATA interface. This
  is currently the most popular drive interface for
  windows based PCs. Introduced in the mid 1980s
  and standardized by ANSI in 1994.
• IEEE 1394 (FireWire, i.Link)- Developed by apple
  Corp and later standardized by the IEEE to
  provide a high speed serial device interface.
  Many components other than drives can be attached
  through a fire wire interface. (introduced in the
  mid 1990s , standardized in 1995)
• USB 1.1 and 2.0- A high speed serial device
  interface. Many components other than drives can
  be attached through a USB interface.

3
IDE/ATA

• ATA up to 8.3 MBps
• EIDE proprietary extensions
• ATA-2/3 up to 16.6 MBps
• ATAPI tape and CD-ROM support
• ATA/ATAPI-4 up to 33 MBps
• ATA/ATAPI-5 up to 66 MBps
• ATA/ATAPI-6 up to 100 MBps
• ATA/ATAPI-7 up to 133 MBps
• SATA up to 300 MBps

4
Speed Improvement Techniques

• PIO modes
• In the original ATA schemes , the CPU was
  involved with every data transfer through a
  scheme called programmed input/output. Five PIO
  were developed with each new level improving
  performance through various techniques. These
  schemes are listed in the following table
• PIO mode 0 3.3 MBps
• PIO mode 1 5.2 MBps
• PIO mode 2 8.3 MBps
• PIO mode 3 11.1 MBps
• PIO mode 4 16.7 MBps

5
Speed Improvement Techniques

• Later Designers came up with direct memory access
  (DMA) schemes that removed the need for the CPU
  to be involve with every transfer. The six DMA
  schemes provided the following performance
  levels.
• DMA modes
• Single word 0 2.1 MBps
• Single word 1 4.2 MBps
• Single word 2 8.3 MBps
• Multi word 0 4.2 MBps
• Multi word 1 13.3 MBps
• Multi word 2 16.7 MBps

6
UltraDMA modes (later improvements)

• UDMA mode 0 16.7 MBps
• UDMA mode 1 25 MBps
• UDMA mode 2 33.3 MBps
• UDMA mode 3 44.4 MBps
• UDMA mode 4 66.7 MBps
• UDMA mode 5 100 MBps
• UDMA mode 6 133 MBps

7
Standard IDE cable
8
80-pin ATA cable
9
SATA data cable
10
Large drive support

• Original Interrupt 13 limit 504 MB
• LBA and ECHSup to 8.4 GB (through sector
  translation)
• Interrupt 13h extensionsup to 128 GB (through
  BIOS changes)
• ATA interface limit up to 137 GB
• Large LBAup to 144 petabytes (144,000,000 GB)
  (through bits/sector and maximum sectors chages)

11
Drive identification

• ATA supports two drives per controller
• One drive is master
• Other drive is slave
• Older drives
• Set jumper or DIP switch
• Connect to cable in correct location
• Cable select

12
Drive identification
Motherboard
Slave
Master
13
Primary and secondary
Secondary IDE
Primary IDE
14
SCSI
15
SCSI device IDs

• Each device must have unique ID
• 0-7 or 0-15
• Higher IDs Higher priority
• Host Bus Adapter would be 7 or 15

16
Termination

• Terminators resistors
• Block signal reflections
• Terminate both ends of the bus
• Terminator blocks or switches
• Passive terminators-Dampens the reflected
  signals through non electronic means.
• Active terminators-An electronic component that
  dynamically tunes itself to match the impedance
  of a cable exactly.

17
Differential SCSI

• Single Ended (SE)signal voltages compared to
  ground
• Differential SCSI
• Data lines are paired
• Signals are electrical opposites
• Signal is read as comparison between wires in the
  pair
• (Ultra SCSI) High voltage differential (HVD) (
  5V)
• (Ultra2 SCSI) Low voltage differential (LVD) (
  3.3V)

18
Other interfaces

• ST506/ST412
• ESDI-used two cables btn the controller and
  interface , one data and the other for control
  signals. It supported a max throughput of 24Mbps.
• USB-USB 1.1 limit data transfere to 12Mbps
  whereas USB 2.0 increases that limit to 480Mbps
• IEEE 1394 (FireWire)