Ep. 23 Expansion Buses-pt 1: System Resources
27th August 2008
Author’s Note: I am breaking this blog posting into two parts. The first part is about System Recourse. The second part is about the types of Expansion Buses.
In the old days of computers the only way to get video, sound or anything else we take for granted in today’s computers required a trip to the computer store. You would have to purchase an expansion card and add it to your computer.
Mr. Ford’s Rambling:
When I was at USF (Tampa), back in the early 90’s we had a suite mate in our dorms (Iota Hall) that had a computer. He bought some type of Mech video game. Later in the semester he went to the computer store and bought a sound card. Once he had the card installed he went back to the software store to buy the expansion pack for the game that added sound. The game did not original come with sound because sound cards were not on the typical system. Sadly, he also did nothing but play video games in his dorm room, so he had to go away the following semester.
When I bought my first computer (the 486) I had to buy an expansion card so I could install a serial mouse. I also had to buy a video card, a sound card, and a modem. My computer only came with a keyboard interface (the old DIN connection) and cost around $2,500.
What does any of this have to do with our topic?
When IBM put together the first PC back in the 80’s they knew that they needed to create in their computers, the ability to add features. This goal was accomplished by the concept of expansion buses.
Expansion Buses are places in the motherboard were the user could install Expansion Cards that add functionality (more bells and whistles) to their computer. Some of the more common expansion cards are sound cards, video cards, network interface cards, etc…
Before we get into the different types of expansion buses, we need to take a quick look at System Resources.
System Resources
In the world of the computer, the CPU acts like a brain. In the computer the CPU and all components must have a way to talk to each other. This method of communication is collectively known as System Resources.
There are four separate methods of communication, each with their own purpose, and job.
The four methods:
- IRQs
- I/O Addresses
- DMA Channels
- Memory Addresses
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