A+ Hardware/Software - 10/9/2007

Today we covered Chapters 4 and 5, which dealt with the I/O (input/output) system of our computers and mass storage in our computers.

Three things I'd like you to remember are IRQs, I/O Addresses, and DMA settings.

• IRQ - How devices talk to the processor. Remember, the interrupt is simply a request and the processor can say no if it needs to (maskable interrupt). However, the device can say NOW! with a non-maskable interrupt. (NMI) Oh, KNOW YOUR IRQ TABLES!! :)
  
• I/O Address - How the processor talks to devices. Processors, despite being the kings of the computers, are pretty polite and can wait on a device if necessary -- the processor just can't do anything else until the device responds.
• Direct Memory Address - These are paths that allow devices to bypass the processor altogether and directly access the RAM. Most of these are obsolete, but make sure that you know that the floppy drive uses DMA 2.

In Chapter 5, we talked about ways to store mass amounts of data, and typically this will mean the hard drive (although we did cover lots of other alternatives). Make sure you know your hard drive "geometry" and be able to identify what tracks, sectors, platters, and cylinders (we didn't go over cylinders today -- make sure you look over your notes from previous classes!)

I also introduced the idea of hard disk arrays, which are collections of hard disks designed to keep our data in one of several methods -- each with their own benefits and drawbacks. Make sure you know the differences between RAID0, RAID1, and RAID5.

Homework:

• Chapter Four - Exam Questions 1-10
• Chapter Five - Exam Questions 1-10