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HDD 6: IDE Interface, Connection (Master, Slave, CS), cabling, UATA100

IDE Interface

(IDE - Integrated Drive Electronics, EIDE - Enhanced IDE),  ATA (Advanced Technology Attachment) 

• At present, the IDE interface is the most widespread interface designed for connecting hard disks. IDE refers to disks and devices with integrated controller. Here are some terms concerning IDE:

• IDE (Integrated Device Electronics) - the first version of this interface was simply called IDE, and also in some cases the newer versions are called the same. This older interface started to improve in the early 90s - it was physically formed of cards called IDE adapters connected through ISA bus (using 8-bit or 16-bit slot) (a picture of a similar multifunction card is placed in the "Interface" article). Later, this becomes unsatisfactory because of the possibility of connecting only two disks of  504MB maximum size and lower transfer rate. In some computers, a cable with one terminal was used, then, to be able to connect the second disk or CD-ROM it was necessary to fix another terminal on the cable or to change the cable (the problem was that in the branded PCs the MB terminal was different and a new cable was difficult to get).

• EIDE (Enhanced IDE) (in the mid-90s it becomes a substitute for the IDE) - this interface has been designed for larger disks. It provides support of up to four devices, possibility of connecting non-disk devices (CDROM, ZIP, ....), very fast data transfer through integrated host adapter connected to the PCI bus.

• ATA (AT Attachment) - Name for IDE and ATAPI standards (particular versions of these standards use different names and trade marks - IDE , EIDE, UltraDMA, UltraATA, FastATA....). 

• ATAPI (ATA Packet Interface) - Non-disk devices using the same cables and having the same electric requirements as the IDE. CD-ROMs, optical disks, tape units and others belong among this devices. 

• Host adapter - sometimes, it is also called a controller for ATA devices, but the truth is that the real controller is a part of the disk and the adapter just provides the connection. In older computers, this used to be solved by help of  a simple or a multifunction card connected through ISA, MCA or VLBUS bus containing one connector for connecting disks (disadvantage of these buses is also their low throughput; at present, it is recommended to connect the disk only through the PCI bus). The multifunction card contains a floppy disk controller and outlets for I/O ports (COM a LPT). For connecting CD, a sound card with an outlet for ATAPI device was used (because of the expansion of the CD drives, the diskettes are continually replacing by CDs). In present computers, the adapter has 2 channels with the possibility of connecting 4 devices. In newer computers, the adapters are called integrated controllers and the terminal for connection leads directly from the MB. 

• If you look for a solution for connecting another four disks you can find some brief information on the controller Ultra ATA/100 Controller Promise TX2 by clicking on this link.

• RAID controller - In case of motherboards with the RAID function, there is another integrated controller on the MB that enables to connect more disks into a disk field or to switch to the function of another controller and then to connect another 4 devices. If another EIDE channel needed, you can use modern adapters on the PCI bus.  

Modes and the data throughput (DTR) of the interface

• DTR - Data Transfer Rate (Burst Rate)

• New versions of the ATA standards are coming thanks higher requirements on speed, capacity and other features. At present, it is e. g. ATA/ATAPI version 6, also known as Ultra ATA/100. Detailed information about standards you can find on the sites of the Technical Committee T13 - www.t13.org. Particular standards primarily differ in the way of communication, speed and some other improvements. Newer standards are compatible with the previous versions. 

• In case of using an interface with lower transfer rate than the disk is able to reach, the disk can be used only partly. It is a waste to use a disk with UDMA/100 on an older computer using only PIO4!

• PIO (Programmed Input/Output) - mode used by older disks and some ATAPI (CD-ROM) devices. The disadvantage of the PIO modes was its controlling by the processor's control commands, sometimes the disks can load the processor up to 90%.

• DMA - Direct Memory Access - There are 8 DMA communication channels in the computer. The devices that support DMA are able to require, get and work with data with lower amount of control commands of the processor. In the disk, this is provided by the disk controller. The speed of the communication here is up to several times higher then in the PIO mode. Utilization for the processor is maximally about 10%. 

• To reach the optimal performance of the disk interface, it is recommended to install the current driver for IDE and chipset. The support you will find on the producers´ sites - Via (4in1), Intel, Sis, ...). 

• PIO Mode 0 - 3,33MB/Sec (t0 - 600ns)

• PIO Mode 1 - 5,22MB/Sec (t0 - 383ns)

• PIO Mode 2 - 8,33MB/Sec (t0 - 240ns)

• PIO Mode 3 - 11,1MB/Sec (t0 - 180ns)

• PIO Mode 4 - 16,6MB/Sec (t0 - 120ns)

• ATAPI intefraces work in different transfer modes 

• Singleword DMA 0 - 2,1MB/Sec (t0 - 960ns)

• Singleword DMA 1 - 4,2MB/Sec (t0 - 480ns)

• Singleword DMA 2 - 8,3MB/Sec (t0 - 240ns), Singleword modes have been replaced by Multiword DMA modes

• Multiword DMA - Mode 0 - 4,2MB/Sec (t0 - 480ns)

• Multiword DMA - Mode 1 - 13,3MB/Sec (t0 - 150ns)

• Multiword DMA - Mode 2 - 16,6MB/Sec (t0 - 120ns)

• Ultra DMA Mode0 - 16MB/Sec (Ultra ATA) (tcyc - 112ns)

• Ultra DMA Mode1 - 20MB/Sec (Ultra ATA) (tcyc - 73ns)

• Ultra DMA Mode2 - 33MB/sec (Ultra ATA/33) (tcyc - 54ns)

• Ultra DMA Mode3 - 44Mb/Sec (Ultra ATA/66) (tcyc - 39ns)

• Ultra DMA Mode4 - 66MB/sec (Ultra ATA/66) (tcyc - 25ns)

• Ultra DMA Mode5 - 100MB/sec (Ultra ATA/100) (tcyc - 16,8ns) - at present and for the present, no disk can take the advantage of this transfer rate. The difference between the performance of recent disks and the Ultra ATA/66 is very low, or rather non. The device usually uses not even a half of the Ultra ATA/100 performance (when there are two powerful disks on one cable, it starts to be close here). In case of faster disks it also depends on the type of the disk controller (VIA, Promise, Intel...).

• Ultra DMA Mode6 - 133MB/sec (Ultra ATA/133) - a new product appearing in the second half of 2001 on the market. Increased speed and improved error control - CRC. (see Fast Drives Technology - www.maxtor.com/fastdrive). 

• t0 - Cycle time

• All standards are always compatible with previous versions, but never with the higher ones - a disk with 66MB you can use on a 100MB controller, but to use a 100MB disk on a 66MB controller is a waste, however, it is also possible but with the performance that will be not used for 100%.

• Some users tend to use the numbers 33, 66, 100 to define the bus rate quoted in MHz, but this is wrong! These numbers mean maximal data throughput for a bus and represent the standard!

• Avoid making mistake in defining disk's speed. Many people think that by buying a disk with UDMA/100 they get up to 30% more over against similar disk with UDMA/66. Unfortunately, this is not right. The difference in the performance makes about several percent, in the successful cases.

• For the Ultra ATA/66 mode and higher you have to use 80-wire cable that has the same terminal on both ends (40 pins), but there is a wire put between each conductor. This wire only serves for avoiding electromagnetic interference. This new cable is limited by its length. 

• The current mode is displayed when the computer is started or when you are using some diagnostic SW under Windows.

Connection (Master, Slave, CS), cabling, UATA100 

• The connection must be only made when the computer is off. There is an exception - special types of SCSI disks connected when working (so called hotswap disks).

• 1. configuring the disk as Master or Slave. In most disks, it is set up by the producer as Single, it means as the main disk with no other disk present. 

• 2. fixing the disk into the computer case. If you do not do this, the disk is more sensitive to shocks when transferring it and when working, too. For the fixation, little screws are used.

• 3. Connecting the data cable to the motherboard and to the disk. It is very important to connect the pin 1 correctly (red cable). If you do not do this right, then the disk cannot be detected, or in most cases the computer cannot be started at all. Some cables contain protection against wrong connection - sealed up pin No. 20 on the cable and no pin No. 20 leading from the device or the MB (Another solution is a cut on the connector).

• 4. Connecting feeder cable. 

• 5. Configuration by help of jumpers

• 6. BIOS system setup (In case of older computers,  it is recommended to write down the parameters from the disk or when transferring the disk from computer to computer to  write down the parameters set in the BIOS system. In most newer disks just choose the automatic detection).

• 7. Dividing disk and formatting partitions.

• Other connection - In case of a CD drive you must connect an audio cable, in case of disks you must connect a cable leading from the LED diode signalizing the disk's activity (to the MB).

Master or Slave - Primary or Secondary?

• Primary (IDE1) - main controller on the motherboard to which you can connect the data cable with terminals for 2 devices. 

• Secondary (IDE2) - the second controller on the motherboard with the possibility of connecting another two devices. 

• Master (MA or device0) - Main disk or another device on the cable configured as the first one. If you have more disks, the disk containing an OS should be configured as Master on the main controller.

• Slave (SL or device1) - a disk or another device configured as the second one

• Cable Select (CS) - If a device is Master or Slave is defined by the cable's terminal. On the second cable the device is defined as Master and when it is connected on the connector in the middle, then it is Slave. Me, I personally prefer manual definition of Master and Slave device (here, it does not depends on the disk's position according to the cable).  

• Single - settings for the device that is single on the cable. In some cases, such devices also accept the master and slave values (especially in case of CD drives where I have never met the "single" setup). 

• The setup is made by help of  jumpers. See the example from the disk by Western Digital. Each disk has its specific settings which should be available in a manual, on a label or on the producer's internet sites, or you can also find it on some specialized web sites containing disk documentation.

• There must always be one device set as Master and another device as Slave on each cable. When the devices are configured equally, they will not be detected correctly. There is just one exception - Cable Select setup (if supported).

• Other settings can serve for testing or for another purposes created by the producer. 

There should be some help contained on disks or in the documentation - this is from the Western Digital 153BA disk

• When using two devices having different communication modes (e. g.. PIO4 and ATA66), the speed can be subordinated to the slower device (be aware of the CD drives with PIO4).

Cables

• Most often used cables are ribbon cables for EIDE. Here are two types of them - 1. 40-wire cable for UATA/33 devices and lower, 2. 80-wire for UATA/66 devices and higher. In the 80-wire cable, the data wires are interlarded with grounding conductors which avoid crosstalks. 

• In some cases, the cables can be shortened. To put the connectors back you must use special tongs, but sometimes you can also manage to do it without them. The connector must be attached to the ribbon cable properly. 

• It is advisable for better fixing to tie up the cable with a rubber band and to keep it carefully away from other cables and from the fan - so you avoid electromagnetic interference and support the air flow. 

80-pin cable

A3 = max. 457mm

A2 = min. 127mm

A1 = max. 152mm

• Blue connector serves for to be connected into the controller on the motherboard. Black connector serves for the Master device, and the grey one for the Slave device. 

• When connecting one device, it must be attached to the end of the cable, it may not be connected to the connector in the middle, because this is designed for the second device!

40-pin cable 

A3 = min. 257mm max. 457mm

A2 = min. 127mm max. 304mm

A1 = min. 127mm max. 152mm

Connector extension for NTB (no other feeder cable used)

Requirements for the full use of UATA/100

• A disk or a device with enabled support of UATA/100

• 80-wire cable (detection of the cable type goes automatically)

• EIDE controller supporting UATA/100 - in newer motherboards, it is an integrated adapter where the UATA/100 support is a part of the chipset for output devices. In some older ones a UATA/100 controller can be used in the form of a card put into the PCI slot.

• Support of the used operating system with enabled support of UDMA - e. g. in Windows 98 the DMA mode is disabled, so it must be enabled in the disk settings or in case of the MB with VIA chipset it must be enabled when installing the 4in1 service pack. Be careful in order not to install controllers older than the contained in the system. In Windows 2000 you have to install the service pack 2 to get the VIA and UATA/100 controllers support. 

• If some of the conditions are not fulfilled, a lower mode is used - it means UATA/66, UATA/33 or even PIO4.

• In some cases the BIOS system support is needed, where you can among other functions disable using of UDMA.

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