• Choose a category
• All
• Classic-Fiction

* * *

NOTE Bus mastering devices ignore the DMA controller; they don’t have DMA channels.

If you want to see your DMA usage, head back to the Device Manager and change the view to Resources by type. Click on Direct memory access (DMA) and you’ll see something like Figure 8-25. This system has only two DMA channels: one for the floppy drive and one for the connection to the CPU.

Figure 8-25 DMA settings in the Device Manager

One interesting note to DMA is that neither PCI nor PCIe supports DMA, so you’ll never find a DMA device that snaps into these expansion buses. A hard drive, floppy drive, or any other device that still wants to use DMA must do so through onboard connections. Sure, you can find hard drive and floppy drive cards, but they’re not using DMA.

Memory Addresses

Some expansion cards need memory addresses, just like the system RAM. There are two reasons a card may need memory addresses. First, a card may have onboard RAM that the CPU needs to address. Second, a few cards come with an onboard ROM, the so-called adapter or option ROM you read about in Chapter 5, “Microprocessors.” In either of these situations, the RAM or ROM must steal memory addresses away from the main system RAM to enable the CPU to access the RAM or ROM. This process is called memory addressing. You can see memory addresses assigned to expansion cards by clicking on Memory in the Device Manager when viewing resources by type.

The key fact for techs is that, just like I/O addresses, IRQs, and DMA channels, memory addressing is fully automatic and no longer an issue.

Installing Expansion Cards

Installing an expansion card successfully—another one of those bread-and-butter tasks for the PC tech—requires at least four steps. First, you need to know that the card works with your system and your operating system. Second, you have to insert the card in an expansion slot properly and without damaging that card or the motherboard. Third, you need to provide drivers for the operating system—that’s proper drivers for the specific OS. Fourth, you should always verify that the card functions properly before you walk away from the PC.

* * *

NOTE Some manufacturers insist on a different order for device installation than the traditional one listed here. The most common variation requires you to install the drivers and support software for an expansion card before you insert the card. Failure to follow the manufacturer’s directions with such a card can lead to hours of frustration while you uninstall the card and reinstall the drivers, sometimes manually removing some drivers and software from the system. The bottom line? Read the instructions that come with a particular card! I’ll provide more specific examples of problem devices in later chapters.

Step 1: Knowledge

Learn about the device you plan to install—preferably before you purchase it! Does the device work with your system and operating system? Does it have drivers for your operating system? If you use Windows, the answer to these questions is almost always “yes.” If you use an old operating system such as Windows 98 or a less common operating system such as Linux, these questions become critical. A lot of older, pre-XP hardware simply won’t work with Windows XP or Vista at all. Check the device’s documentation and check the device manufacturer’s Web site to verify that you have the correct drivers. While you’re checking, make sure you have the latest version of the driver; most devices get driver updates more often than the weather changes in Texas.

For Windows systems, your best resource for this knowledge is the Windows Logo’d Products List. This used to be called the Hardware Compatibility List (HCL), and you’ll still hear lots of people refer to it as such. You can check out the Web site (http://winqual.microsoft.com/hcl/Default.aspx) to see if your product is listed, but most people just look on the box of the device in question (Figure 8-26).all Windows-certified devices proudly display that they work