CST8174_Lecture_22_Expansion_slots

CST8174_Lecture_22_Expansion_slots - Algonquin College...

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Unformatted text preview: Algonquin College CST8174 CST8174 Computer Technology Basics Expansion Bus Wednesday, May 6, 200 8 - 2 Algonquin College CST8174 Expansion Bus Every device in the computer connects to the external data bus and the address bus The internal components run on the front side bus usually at the system clock speed All components need to run at the same speed at the bus that is accessing them Since system clock speeds vary, an extension to the external data bus that runs at a standardized speed was needed Wednesday, May 6, 200 8 - 3 Algonquin College CST8174 Expansion Bus This was accomplished through the expansion bus or I/O bus The expansion bus has its own clock speed, much slower than that of the front side bus The chipset acts as a divider between the two busses, compensating for the speed difference Enables you to add devices to your computer to expand its capabilities Wednesday, May 6, 200 8 - 4 Algonquin College CST8174 8-Bit ISA Bus Industry Standard Architecture Designed for use with the 8088 processor Expansion slot has an 8-Bit external data bus connection Originally ran at a set speed of 4.77MHz Provides 8 data lines and 20 address lines enabling slot to address 1MB of memory IBM enabled competitors to copy the PC bus without having to pay a licensing fee or royalty Wednesday, May 6, 200 8 - 5 Algonquin College CST8174 Wednesday, May 6, 200 8 - 6 Algonquin College CST8174 16-Bit ISA New bus for the 286 that took advantage of the new 16-bit external data bus Uses the same 8-bit connector of the original ISA bus with an optional 16-bit extension Fully backwards compatible allowing you to plug an 8-bit card into it Used the same crystal as the 8-Bit ISA bus to ensure total compatibility Increased speeds to 8.33MHz Wednesday, May 6, 200 8 - 7 Algonquin College CST8174 Wednesday, May 6, 200 8 - 8 Algonquin College CST8174 Limitations of ISA It was slow, running around 7MHz and a top speed of 8.33MHz It was unable to handle the 32-bit and 64-bit external data busses or more modern processors Some vendors attempted creating their own proprietary 32-bit busses The release of the 386 created a huge demand for a superior bus Wednesday, May 6, 200 8 - 9 Algonquin College CST8174 MCA Bus Micro channel Architecture Had a 32-bit bus to match the 386 and 486 Runs at a faster speed of 12MHz Had the capabilities to self-configure devices The slot layout was different then ISA, making it not backwards compatible IBM strictly licensed the technology Wednesday, May 6, 200...
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CST8174_Lecture_22_Expansion_slots - Algonquin College...

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