tailieunhanh - A complete illustrated Guide to the PC Hardware phần 9

-Die bộ nhớ cache cho hiệu suất tốt nhất. Việc giảm kích thước L2 từ 512 đến 256 KB là ít quan trọng hơn, tốc độ xung nhịp đầy đủ có tác dụng rất lớn. Chip Thunderbird thực hiện tốt như hoặc tốt hơn một chút so với Pentium III chạy ở cùng một tần số đồng hồ. | A Guide to Adapters and I O units. We want YOU to take this survey Please click the banners to support our work . Module 5a3. About IRQs DMA bus mastering etc. The contents Next page Previous page . IRQ . DMA Bus mastering IRQs top When you install an expansion board in a slot it gets connected to the I O bus. Now the board can send and receive data. But who regulates the traffic Who gives clearance to the new controller to send data It would appear that data traffic could soon be chaotic. Please support our sponsor. To control data traffic on the I O bus the concept of IRQ Interrupt ReQuest was created. Interrupts are a fundamental principle in the PC design. There are two types of interrupts Software Interrupts are used to call any number of BIOS routines. Hardware Interrupts are the subject of this page. Hardware Interrupts top http hardware 1 of 9 7 27 2004 4 09 13 AM A Guide to Adapters and I O units. The adapter or unit on the I O bus uses the interrupt to signal request to send or receive data. An interrupt signal is like a door bell. The unit signals by applying a voltage to one of the wires in the bus - an IRQ. When the CPU acknowledges the signal it knows that the unit wants send or receive data or is finished. The advantage of IRQs is that the CPU can manage other tasks while an adapter massages its data. When the adapter has finished its task it will report to the CPU with a new IRQ. As an example let us see how keyboard data are handled. The keyboard send bits serially through the cable to the keyboard controller. The controller organizes them in groups of 8 one byte . Every time it has a byte it sends an IRQ to the I O bus. The IRQ controller asks the CPU permission to use the bus to send the byte to wherever. The IRQ controller reports back to the keyboard controller giving clearance to send the next character byte IRQ wires Physically the IRQ is a wire on the bus. This wire connects to all expansion .