Chapter 42. I/O and The south bridge

We now looked at the various buses of input-output, and the bridge of the south of the tiddlywinks plays the central role in the transfer of the data on these buses. But, as mentioned front, the bridge of the south is helped by a small superb controller of input-output. Let briefly describe it to me.

Functions of the bridge of the south

The bridge of the south is a piece on the mother chart. If we want to look at one of the last models, we could take the bridge of the south of the tiddlywinks of Intel 915, which is designed for mother charts with processors of Pentium 4.

Diagram 191. Tiddlywinks 915G of Intel. The bridge of south ICH6 is towards the left.

A glance on the characteristics of the piece indicates that it contains the components and the functions following:

Component	Description
DMI	The direct interface of media is connection with the memory with a maximum bandwidth of 2 GB/sec.
PCI Express	bus Safety-speed for adaptors of input-output
Ports of NCV	Standard bus of input-output.
Serial ATA	Controller for to four hard drives of SATA
Storage of Matrix	The advanced interface of controller of host centre for RAID 0 and 1 on the same thing led. Including the support of Native Command Queuing and hot exchanges of drive of catch.
Ultra Ata/100	The controller for devices of PATA like the hard drives, DVD- and Cd-lead.
Ports of USB	ports of USB 2.0 Safety-speed.
acoustics of 7.1 channels	Option for the healthy device integrated with the edge, Digitals dolby and the SDR.
Modem AC97	Integrated modem.
Ethernet	Integrated 10/100 network of put-band controller.

Diagram 192. Functions chosen in a bridge of the modern south.

But a certain number of traditional controllers for the reader with floppy disc etc are absent. Those can be placed in the superb controller of input-output.

Superb input-output

The so-called superb controller of input-output is found on all the mother charts. It is a piece of assistance, which deals with certain number less demanding functions of controller for the bridge of the south.

The tasks of the superb controller of input-output are completely well defined: that is thus perfect to employ a piece produced in series and standard, which can be employed on practically any mother chart. This helps of the prices of subsistence to the bottom, and these superb controllers of input-output come from the companies like Winbond and ITE.

Diagram 193. A superb controller of input-output of Winbond.

The superb controller of input-output is connected to the bridge of the south using a bus at fallback speed special, and this architecture is called the LPC (low account of Pine). The piece is a piece of 128 terminals containing these components:

Controller	Description
FDC	controller 82077 with compatible floppy disc
UART	Carry series, compatible controller 16550, including IrDA (infra-red)
LPT	Parallel wearing of printer
Play	For a handle
KBD	controller of keyboard 8042 compatible
PS/2	Wearing of mouse
LED	Order the small LED in the box
Ventilator	Order the ventilator

Diagram 194. Functions of which the superb piece of input-output takes care typically.

You will find many various provisions of the mother chart. The bridge of the south can be connected to other pieces of controller. �This could be:

�

��������� A controller of RAID (for example of the promise or Highpoint, to see fig. 228, or the controller of SCSI (of Adaptec). � ��������� An operational processor (for example of creator or Yamaha). � ��������� A controller of Ethernet. � ��������� A controller of cable of fire, and much more. It belongs to the various board manufacturers mother to decide how they will employ the tiddlywinks. The bridge of the south offers loads of the equipment which can be applied so desired. For example, some bridges of the south have the integrated primitive healthy devices (based on standard AC-97). This uses the central processing unit of treatment to treat the noise. On some mother charts this functionality will be put at the use, whereas other manufacturers choose to integrate �a true� healthy piece, for example, of creator. In any case, some users will choose to install a separate healthy chart with good more functionality - independently of which noise comprises the offers of mother chart. Diagram 195. A situation as a whole of the many equipment of input-output offered by the bridge of the south. Periodic and parallel ports The periodic and parallel ports are included in the system of input-output, and their controller is located in the superb controller of input-output. The PC is equipped at least (usually two) with the doors series asynchronous. They are the male connectors on the back of the PC, which has 9 or 25 terminals, of which often only 3-4 are employed for the serial transmission. The parallel port is also called the wearing of printer, because is it for what it is normally employed. The connector of printer on the back of the PC is a connector female of 25 terminals. Diagram 196. In the medium you see the red parallel port and the two green doors series. The ports are also called COM1, COM2 and the LPT. They are so-called names of logical Apparatus, which the programme of starting of PC automatically assigns with these devices during starting, just like a:, C: , the SWINDLE, the PRN and the KBD are logical names. Diagram 197. The logical name, COM1, refer to a periodic port of input-output. Today the periodic doors series and devices are used much less than they were. It is particularly due to the bus of USB, which can connect the equivalent devices. But if you use, for example, a modem based by USB, it you will comprise just as if it were a normal periodic device. Below the ISDN an adaptor is installed, which is connected via the USB. It creates two virtual ports of COM which can be seen using the director of device. In this way the program commutated of Internet can use the device of USB in the same way as if it were connected to the port (physical) of COM of a: Diagram 198. Ports COM3 and COM9 are really a device of USB. Asynchronous transmission The doors series function using the asynchronous transmission, which it could be interesting to know a little. The asynchronous transmission means that data can be transferred to irregular intervals, as you could already know about use a modem. The transmission starts only when the receiver is ready to receive. And the receiver can spend unlimited time� to digest� the data. The opposite principle is synchronous transmission, where a divided clock order the step. The irregularity means that you must be able to establish when to send data, and when part of data was sent completely. This is carried out using a protocol, which define the lengths of package, etc, on which the shipper and the receiver must agree. When the shipper does not have anything to say, a jet of 1 is sent. To the beginning of a transmission, one 0 is sent. After this starting bit, the data are introduced the parts of 5,6,7 or 8 bits. Then follows 0,1 or 2 so-called bits of parity, which are used to carry out a simple control on the transfer, and the package is closed with 1 or 2 bits of arre4t. The most common standard is 8 bits of information, no bit of parity and 1 bit of arre4t. This system is often called the 8/N/1. Diagram 199. In a periodic transfer, the data are packed in the small, various parts, which are sent after the other. The� packing� necessary of the data in parts for the serial transmission takes place in the piece of UART, which belongs to the superb controller of input-output. The UART represents the transmitting receiver/asynchronous universal. The piece of UART converts the train of data of data between the parallel bus of input-output and periodic connection. Bytes of the bus of input-output must �be crossed upwards� in the series of little and �framed� with bits of arre4t, etc, and this takes place in the UART. Diagram 200. The controller of UART remballe of the data in order to be able to carry out a periodic transfer.