tailieunhanh - A complete illustrated Guide to the PC Hardware phần 2

ISA xe buýt nội bộ, được sử dụng trên các cổng đơn giản, như bàn phím, ổ đĩa mềm, nối tiếp và cổng song song. Khi xe buýt mở rộng bên ngoài, có thể được kết nối với 16 bộ điều hợp ISA cắm ISA được ngày hôm nay chủ yếu được sử dụng cho 16 bit thẻ SoundBlaste | An illustrated Guide to I O-buses The ISA bus has two faces in the modern PC The internal ISA bus which is used on the simple ports like keyboard diskette drive serial and parallel ports. As external expansion bus which can be connected with 16 bit ISA adapters. ISA slots are today mostly used for the common 16 bit SoundBlaster compatible sound cards. Problems The problem with the ISA bus is twofold It is narrow and slow. It has no intelligence. The ISA bus cannot transfer enough bits at a time. It has a very limited bandwidth. Let us compare the bandwidths of ISA bus and the newer PCI bus Bus Transmission time Data volume per transmission ISA 375 ns 16 bit PCI 30 ns 32 bit Clearly there is a vast difference between the capacity of the two buses. The ISA bus uses a lot of time for every data transfer and it only moves 16 bits in one operation. The other problem with the ISA bus is the lack of intelligence. This means that the CPU has to control the data transfer across the bus. The CPU cannot start a new assignment until the transfer is completed. You can observe that when your PC communicates with the floppy drive while the rest of the PC is waiting. Quite often the whole PC seems to be sleeping. That is the result of a slow and unintelligent ISA bus. Problems with IRQs http hardware 2 of 5 7 27 2004 4 06 04 AM An illustrated Guide to I O-buses The ISA bus can be a tease when you install new expansion cards for example a sound card . Many of these problems derive from the tuning of IRQ and DMA which must be done manually on the old ISA bus. Every component occupies a specific IRQ and possibly a DMA channel. That can create conflict with existing components. Read module 5 about expansion cards and these problems. The ISA bus is out As described the ISA bus is quite outdated and should not be used in modern pcs. There is a good chance that this outdated legacy technology quoting Intel will disappear completely. The USB bus is the .