pp 197-209
Lesson 4.6 Corridors and regional expansion slots
- Architecture for regional corridors
- The corridor ISA (Industry Standard Architecture)
- The corridor EISA (Extended Industry Standard Architecture)
- The local regional corridor
- The corridor VL-BUS (VESA Local bus)
- The corridor PCI (Peripheral Component Interconnect)
- The corridor AGP (Accelerated Graphic Port)
- Summary
When you have completed this course you will:
• Explain the architecture of corridors used by peripherals to personal computers
• Explain the necessity of regional corridors
• indicate the type of regional corridors, expansion slots and expansion cards used in personal computers
• Explain how various corridors of a personal computer are connected
4.6.1. Architecture for regional corridors
As we have seen, the runway system is one that allows communication between all units of the computer. In order for a computer system to be scalable, the corridor should be accessible from units that are not present in the original system design. In other words, make it easy to connect new peripherals on the system path. These regional units of personal computers in the form of expansion cards and expansion slots are connected to the motherboard. Such an expansion card shown in Figure 4.6.2. The card is linked to one of the expansion slots as shown in Figure 4.2.3.
Because peripherals are usually slow and can not operate on frequencies that works great editor, personal computers are designed with additional corridors for regional units, which operate at lower frequencies than that of the processor.
As the demands of the software are increasingly used as more and more multimedia technology comes the need for faster peripherals and hence regional quickest route.
4.6.2. The corridor ISA (Industry Standard Architecture)
The first regional corridor that appeared on a personal computer runway is ISA (Industry Standard Architecture - Industry Standard Architecture). This corridor was the first personal computer, which was based on the processor Intel 8088 the company had an operating frequency of 4.77 MHz. This corridor was nothing more than the same processor of the aisle, who came into an expansion slot type ISA. Ranged data 8 bits, 20 bits address range and of course worked on the same frequency as the processor. He later appeared with ISA corridor width 16 bits data width and address 24 bits, which is faster than the previous because it can transfer data at double (16 bits instead of 8 bits).
As technology progresses, processors operating at increasingly higher frequencies. The circuits used in type ISA expansion cards often unable to operate at these high frequencies, creating problems in the computer. So came a standardization that determines the maximum operating frequency of the runway at ISA 8,33 MHz. In this way it was certain that the cards are designed with this standardization would work properly on all personal computers. Since the passage ISA now operates on a different frequency than the processor, it is necessary to use a bridge to connect the two corridors.
The corridor ISA, when operated at maximum allowable frequency of 8,33 MHz, can transfer data at a maximum speed of 4 MBytes / sec in the case of 8 bits and 8 MBytes / sec in the case of 16 bits.
Figure 4.6.1: Expansion Slots ISA 8 bits (bottom) and 16 bits (above). In the left part of the host ISA 16 bits are the additional rows of data, address and control
Figure 4.6.2: ISA expansion card type of 16 bits. At the bottom of the contacts to discern which plugs into the expansion slot
4.6.3. The corridor EISA (Extended Industry Standard Architecture)
The corridor EISA (Extended Industry Standard Architecture - Extended Industry Standard Architecture) is designed as an extension of the runway ISA. He appeared with the company's 80386DX processor Intel, who was the first processor for personal computers with strip width data 32 bits. The purpose of this standardization was to increase the width of the corridor ISA from 16 to 32 bits while maintaining compatibility with the latter. At the same time increased the range of addresses from 24 bits to 32 bits. The maximum operating frequency of the EISA corridor remained the same as the runway ISA, at 8,33 MHz. This means that in combination with the increased range of data word treadmill EISA can carry up to 33 MBytes / sec.
The corridor appeared EISA a time when the software running on personal computers began to have increasing demands on speed. Due to the limitation of the maximum operating frequency of the 8,33 MHz, the runway EISA could not meet the requirements of the software, so soon replaced by newer technology corridors. So while today for compatibility reasons we continue to meet the corridor ISA, EISA, the corridor is gone for good. For this reason you will not talk more on this corridor.
4.6.4. The local regional corridor
As we saw in all these types of regional corridors, the maximum operating frequency is set at 8,33 MHz. Figure 4.6.3 shows the diagram of a personal computer using regional corridors like those mentioned above.
Figure 4.6.3: Diagram of a typical personal computer corridors
As shown in this figure, the processor communicates with memory through a fast track, but is forced to communicate with all other peripherals via a slow ramp, the maximum frequency of which is 8,33 MHz. Imagine how much speed is limited to a personal computer where the processor is able to communicate with peripherals with frequency up to 100 MHz and instead forced them to communicate with a maximum frequency of 8,33 MHz. The limitation of that speed may not be noticeable when it comes to slow peripherals such as keyboard or serial port, but it is annoying when you're dealing with peripherals that speed is critical. Such peripherals are the display and storage. Especially in recent years as operating systems like Windows and OS / 2, have a graphical user interface, there is an increased need for high-speed communication with the processor peripherals.
Solution to this problem came to give the architecture of the local regional corridor. As shown in Figure 4.6.4, this architecture provides for connecting peripherals directly on the corridor of the processor. The term "local roads" arose because most peripheral units may have access to the runway as it was "local" to the processor and memory.
Figure 4.6.4: Diagram of local corridors PC
These regional units can be either embedded on the motherboard, so it is easy to connect them to the local corridor or as expansion cards, which must be connected to special expansion slots of the local hall. Of course these expansion slots should be different from those of the ISA and EISA corridors so there is no risk of placement of slow expansion cards to local fast corridor.
4.6.5. The corridor VL-BUS (VESA Local bus)
Corridor O VL-BUS (VESA Local bus - Local Corridor VESA) is the local path first appeared on a personal computer. The idea was simple: peripherals connected directly to the corridor of the processor and operating in the frequency of this corridor. The data width of this corridor is 32 bits. We can easily calculate that for an operating frequency of the local corridor equal to 40 MHz data transfer rate is up to 160 MBytes / sec (in each beat of the clock 32 bits of data transferred, that is 4 bytes. Therefore 40 million beats in a second clock transferred 160 million bytes, ie 160 MBytes). This speed is significantly greater than in the corridors ISA and EISA. The corridor seemed VL-BUS So to solve the problem of low-speed communication with the processor peripherals.
Figure 4.6.5 shows the expansion slot of the runway VL-BUS. In a personal computer with a runway VL-BUS expansion slots always coexist VL-BUS, for fast peripherals and ISA or EISA for slow peripherals. We see that the expansion slot VL-BUS is used as an additional host of existing ISA or EISA. In this way it is possible to install an expansion card VL-BUS or an expansion card or EISA ISA in the same opening the box of the central unit of the computer.
Figure 4.6.5: Expansion Slot VL-BUS
A standard expansion card type VL-BUS shown in Figure 4.6.6. As we see, this card has some contacts that are connected to the expansion slot ISA or EISA. These contacts are used primarily for getting the card the required power supply and some control signals. Data lines and address the card to get the contacts on the left side of the shape and connected to the expansion slot type VL-BUS.
Figure 4.6.6: Extension card type VL-BUS
The corridor VL-BUS was originally used in personal computers that have processor, which operated at frequencies up to runway 33 MHz. As technology progressed and the operating frequency of processors grow ever, created the same problem that was originally with the runway ISA. The integrated circuits used in expansion cards type VL-BUS could not work properly on these high frequencies. So next was the evolution of computing the runway VL-BUS to be replaced. This corridor is no longer used on any modern computer system.
4.6.6. The corridor PCI (Peripheral Component Interconnect)
The corridor PCI (Peripheral Component Interconnect - Interface Peripheral Component) occurred around the same time with the runway VL-BUS. His aim was, like the corridor VL-BUS, to solve the problem of low-speed communication with the processor of the regional units.
The fundamental diagram of a personal computer that PCI corridor shown in Figure 4.6.7. Unlike the treadmill VL-BUS, PCI treadmill is not connected directly on the local path of the processor, but is a standalone corridor with its own control signals and their own timings. To make this possible, it is necessary to have a special circuit called a bridge PCI. The purpose of this circuit is to achieve communication between the runway and the runway processor PCI while allowing the latter to function independently. In a typical personal computer along with a PCI runway and the runway ISA, which are slow peripherals.
Figure 4.6.7: Diagram corridor PCI PC
The operating frequency of the runway, strict PCI, 33 MHz in order not to appear to be defective expansion cards similar to those that appeared in the hallway VL-BUS. The data width of this corridor is 32 bits. Easily find that the maximum data transfer speed that allows the treadmill PCI is 132 MBytes / sec. Since the corridor operates independently, has the ability to operate in parallel with the runway of the processor. So for example, the processor can use the treadmill for reading data from memory, while data is transferred through the corridor by a PCI peripheral unit to another.
Figure 4.6.8 shows the PCI expansion slot next to an expansion slot ISA. We see clearly the smaller size of the PCI expansion slot and a small shift in position towards the inner part of the motherboard that it is not possible to install ISA cards in PCI slots and vice versa.
Figure 4.6.8: Expansion Slot PCI (above) next to an ISA expansion slot
Figure 4.6.9: PCI expansion card
If we compare the aisle to aisle PCI VL-BUS will see that the first has much better features. Has a better design with clear standards, which allows it to operate faster and more stable, while able to work alongside the runway of the processor. The need, however, the PCI bridge to function, raises the cost of production of motherboards. That is why initially dominated the runway VL-BUS ramp versus PCI. The superiority of the latter, however, coupled with the problems that occurred in the corridor VL-BUS was the reason why the runway eventually prevailed PCI that appears in most modern PCs.
4.6.7. The corridor AGP (Accelerated Graphic Port)
The corridor AGP (Accelerated Graphic Port - Fast graphics port) is the most modern and therefore the fastest personal computer in the hallway. This corridor is based on the runway PCI, designed specifically for the operation of high performance graphics cards and can be connected on the one graphics card. The data width of this corridor is 32 bits while the operating frequency is 66 MHz. This corridor has three modes: the state of the 1X data transfer rate is 266 MBytes / sec, the situation 2X the data transfer rate is 533 MBytes / sec, while the situation is 4X the speed reaches 1066 MBytes / sec.
The graphics card is an expansion card, which is used to connect the monitor to the PC system. The graphics card has a memory RAM, where the processor writes the data you want to portray on screen. Then the graphics card converts the data into specific signals it sends to the screen in order to form the desired image.
Figures 4.6.10 and 4.6.11 show the expansion slot and an expansion card AGP. As we see, the AGP expansion slot is located next to the PCI expansion slots and has a different size and distance from the edge of the motherboard, so it is impossible to insert any other type of expansion card in it.
Figure 4.6.10: Expansion Slot AGP (above) next to an expansion slot PCI.
Figure 4.6.11: AGP expansion card
4.6.8. Recapitulation
As we saw, the first regional corridor that appeared was the runway ISA. With the development of technology came a host of new corridors typically much better than the runway ISA. Table 4.6.1 shows the characteristics of the main routes used in personal computers.
Operating Frequency Range Data Transfer rate
ISA 8 bits 8 bits up to 8,33 MHz 4 MBytes / sec
ISA 16 bits 16 bits up to 8,33 MHz 8 MBytes / sec
EISA 32 bits up to 8,33 MHz 33 MBytes / sec
VL-BUS 32 bits identical to the processor 160 MBytes / sec
at 40 MHz
PCI 32 bits 33 MHz 132 MBytes / sec
AGP 32 bits 66 MHz 266 MBytes / sec (1X)
533 MBytes / sec (2X)
1066 MBytes / sec (4X)
Table 4.6.1: Characteristics corridors PCs
Some of these corridors, including the runway and the runway EISA VL-BUS, no longer used in personal computers. Modern PCs have a PCI treadmill a treadmill and possibly AGP. In all but personal computers even the most modern is the runway ISA. This corridor, although the runway is in the lower features, has become a standard by the appearance of the first personal computer. The computer manufacturers still include the design of their systems for compatibility with existing expansion cards ISA. Just to modern personal computers, the number of expansion slots ISA decreases continuously and take their place PCI expansion slots and AGP.
What did you learn
• The regional corridors allow extending the possibilities of personal computing.
• The corridor is the first ISA regional corridor that appeared but still exists today.
• The local regional corridor allows connecting peripherals directly on the corridor of the processor.
Control knowledge
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