Computer Basics Page 4

Video Cards

The video card controls the quality of what you see on your monitor. It contains all the circuitry necessary for displaying graphics.  It usually is a separate card that fits into one of your motherboard's slots, but sometimes this circuitry is incorporated into the motherboard itself.

When buying a new video card it is very important to "match" it to your monitor. If you've got a fancy new video card and a puny monitor, you just won't be able to view the wonders of your card that you paid good money for. It is a good idea to buy the video card first, then buy a suitable monitor. Better yet, buy the monitor and the card as a set so they will be perfectly matched.

Today's software is increasing in graphics intensity. Even "mundane" business software uses icons, charts, animations, etc. When you add 3D games and educational software to the equation, one can see that there is a crunch in bandwidth for graphical information. With newer software and games getting much more graphics intensive, the PCI bus is maxed out. In fact, the PCI bus, once considered very fast, can now be considered a bottleneck.

Intel knew this. In response, they designed the Accelerated Graphics Port, or AGP. Intel defines AGP as a "high performance, component level interconnect targeted at 3D graphical display applications and is based on a set of performance extensions or enhancements to PCI." In short, AGP uses the main PC memory to hold 3D images. In effect, this gives the AGP video card an unlimited amount of video memory. To speed up the data transfer, Intel designed the port as a direct path to the PC's main memory.

AGP sounds groundbreaking, and it is, no doubt, the latest craze in the need for graphical speed. One reason it is faster than PCI is that, while PCI runs at 33MHz, the AGP bus runs much faster. A 4X AGP bus runs at 4 times 33MHz, or 133MHz! Also, a normally clocked PCI bus can achieve a throughput of 132MB/s. Yes, this is fast, but when compared to the throughputs of 3D games, one finds that it is not enough. AGP, running in 2x mode (2 x 33 = 66MHz), can achieve a throughput of 528MB/s! AGP pulls this off by constantly transferring data on both the rises and falls of the 66MHz clock cycle. Also, AGP makes use of sideband transfers and pipelining so it can constantly transfer data without depending on other components in the PC.

The pipelining ability of the AGP bus is a key point that explains why it provides a performance advantage. Since AGP pipelines operations it can process quicker and more efficiently than PCI bus can. AGP uses a special organization process for all pending and processing requests. In effect, the bus can process one instruction while still receiving the next instructions. This allows much more to be accomplished in a shorter amount of time.

One can easily see why the need for a new graphical interface is needed. While PCI served us well, and still continues to do so, it is bogged down by the demand of full screen 3D graphics. It works great for 2D business software and most games, but intense 3D challenges the bandwidth limitations. For true 3D, there is much information that must be transferred for a single image.

AGP, as stated above, uses the main PC memory to store all 3D information, including textures and the Z-buffer. This rids us of a prime problem of PCI video. Textures add reality to what we see on screen. The Z-buffer creates an illusion of depth. Both of these take up loads of memory, and they use the same chunk of memory. Therefore, manufacturers were forced to choose between textures or the z-buffer. Often, they had to design software that was weak in both areas in order to deal with the PCI bus. With AGP, this restriction is gone.

To create lifelike 3D images, the CPU must perform intensive 3D calculations. The graphics controller processes the texture data and bitmaps. In many cases, the controller must read elements from 7 or 8 different textures and average them into a single pixel on the screen. When this calculation is performed, the pixel must be stored in the memory buffer. Because these textures are so large, they cannot be stored on the video card's buffer. With AGP, they instead are stored in the main system memory. Because of this, it is recommended that you have a large amount of system memory in your machine. This should be no problem due to the low prices of RAM. Intel, no doubt, took this into account when they decided to use your RAM for graphics.

To access the texture data from the main memory, AGP uses a technique called Direct Memory Execute, or DIME. In short, this connects the memory directly to the AGP/PCI chipset. This lets the graphics card access the textures in the main memory, which is limited only by the amount of memory you have in your system.

Like PCI, AGP uses a 32-bit connector. But, there is a difference. The AGP connector has 64 contacts, just like the old MCA adapter. AGP uses a 64-bit wide data path. This extra contact provides new roadways for the pipelining and queuing of data requests. Another difference is that AGP uses an extra eight sideband address lines that allows the controller to issue simultaneous commands while also accessing all 32 of the main data pathways. This is called Sideband Addressing, or SBA. All this comes together to give AGP a faster throughput then PCI.

The Requirements

AGP is still in the preliminary stages. Although it works, the support for it is not adequate for most users.

In order to use AGP with the P2, you must have a motherboard with Intel's 440LX or BX chipset. All such boards offer SDRAM support, an absolute must have for AGP. If you want to use AGP with a Socket 7 processor, you'll find yourself using chipsets like the Via Apollo VP3 and the ALI Alladin V.

AGP also requires software support, including both the OS and graphics drivers. Windows 95 and NT4 can be modified to support AGP, but Windows 98 has built-in support. NT5 will have built-in support for AGP. Windows 95 users can get the Windows 95 OEM Service Release 2.1 or a patch program called USBSUPP.EXE. Your current Win95 PCI device driver will support AGP, but you will need to get DirectX5, which is the only version of DirectX to support DIME. You must make sure your video drivers include VGARTD.VXD as well. This is a virtual device driver that turns on the DIME feature.

Most mainstream graphics card vendors have produced AGP versions of their PCI based video cards. Among these are ATI, Diamond, Matrox, NVidia, STB, and Number Nine. These AGP cards are not always all they are cracked up to be. Each vendor implements a different set of 3D instructions and effects. Some vendors implement these effects through software, a practice that negatively effects performance.

Often, these AGP cards come with a large amount of video memory. 4 MB is minimum, with 8 MB being more standard. Some offer support up to 16 MB of RAM. This video memory gives a large amount of space for texture storage.

The Reality

At this point in the development of AGP, I would not recommend going out of your way to upgrade your system to AGP. The benefits over PCI video are definitely staggering, but the hardware required to support it in the first place can be rather staggering to the typical PC user still using a low-end Pentium PC.

Reviews indicate that many AGP video boards do not perform significantly better than their PCI counterparts. With some boards, AGP makes no difference at all. But, these reviews sometimes do not make mention of the fact that, like MMX, AGP requires software to actually take advantage of it. Without proper software support or software that would ever benefit, AGP will provide little improvement.

Installing Video Cards

Installing a video card is pretty simple. You can do it yourself easily. All you need is a screwdriver and your video card installation instructions. You may want to also create a system disk to rescue your system in case of trouble, although it is unlikely you will get into trouble.

1. First you have to remove the old video card. Unplug the monitor and any other connectors from the back of the video card. Then take the case off and find the video card. If you don't know which one is the video card, find the one the monitor plugs into. That's it. Unscrew the screw that fastens it to the computer. Save the screw. Then gently pull the card from its slot. It may be easier to rock the card back and forth a little to pry it loose, but don't break the slot (if I really need to say that).
2. If you have a separate video card, you can skip this step. This applies to you guys with integrated video circuitry on your motherboard. Some computers don't have a video card, but instead the monitor plugs into the motherboard. In this case, you must disable this circuitry before installing a separate card. You may need your motherboard's manual for this one, but most of them have a small switch or jumper to flip that disables this. 
3. Next, pick the slot you are going to use for the card, and remove the corresponding slot insert from the back of the computer.
4. Now you can insert the new card. Move any cables out of the way. Position the card over the slot, with the monitor connection facing the back of the computer. Line up the pins on the card with the slot. Then push down. It may help to insert one side of the card first, then the other. Don't be afraid to push. It sometimes takes some force to get the card in. Just use your own judgment. Don't break anything.
5. Screw that screw you saved down into place to secure the card. The screw just needs to be snug. You don't want to strip it.
6. Put the case back on, plug everything back in. If your card comes with any external parts, like the Matrox G400 video card does, connect this stuff now.
7. Turn the system on. Hopefully you see the boot screen. That means it works. When you go into Windows, it should automatically detect the new hardware and ask for drivers.  Don't let Windows install stock drivers. Always click "Have Disk" and use the manufacturer provided drivers.
8. Go through the installation routine and install all the drivers according to the software prompts.
9. Optional: After everything is done and working, you probably won't want to mess with it. But, you may want to eventually go to the manufacturer web site and download the latest video drivers for your card. Since video drivers are so key to the system, buggy ones can cause your system to do many strange things from wavy lines to random reboots.

Installing Video RAM

Most of the time, you will never need this tutorial. Let's make that clear from the start. Video cards are changing so fast that by the time you want more memory, you guy a new card. Plus, most modern cards don't come with slots for additional memory.

That said, upgrading your video RAM is relatively easy. The biggest thing to consider is whether it is worth it for you. On most business systems, as little as 1MB of video RAM is enough, although all cards come with more than this now. This will allow you to display 65,000 colors at a 640x480 resolution or a 800x600 resolution. If you try to jack the resolution up to 1024x768, though, you can only show 256 colors. In a case where you want higher resolution AND more colors, you may want to add VRAM to your video card. But, also, before deciding you want more resolution, consider your monitor. Some older monitors can only support 800x600 or lower. Besides, a higher resolution may not be good for the size screen you have. Usually, a 1024x768 resolution only looks good with a 17" or larger monitor.

Also, adding more video RAM will not necessarily make your video card run any faster. It will only allow it more colors at higher resolutions. If you're out for speed, you need to upgrade your entire video card to a graphics accelerator. Many companies, such as Matrox and Diamond, make great SVGA graphics accelerators. For gaming, buy a high-end PCI or AGP video card with 16 MB or more of memory. If you have the supporting hardware, you should get an AGP card.

Installing the VRAM

1. Turn off the system and unplug it. Remove the case cover. Locate your video card. Ground yourself, and remove your video card. Lay the card on a flat surface.
2. Get the RAM chips. VRAM chips are small, rectangular chips with pins on each of the longer sides. Each of the chips will have a small dot on one corner. Likewise, each VRAM socket will have one beveled corner. Match the chips dot into the same corner as the beveled corner on the socket. Make sure the pins on the RAM chip line up with the grooves on the side of the socket.
3. Press the chip into the socket firmly. Don't push too hard to damage the card. Press just hard enough to get it in. You may need to rock it a bit. The chip should not fall out of the video card if turned upside down.
4. Install any other VRAM chips the same way.
5. Reinstall the video card and boot the machine. Run some tests to see if the new memory is being used. You could try running a diagnostic utility to see if it senses it. You could also try pumping up your colors or resolution and see if it works. If not, try reinstalling the RAM. If this doesn't fix it, call the manufacturer. There may be something wrong with the new VRAM or video card.

Video Optimization

Your video settings can influence the performance the entire machine. But also there are factors of video performance and video quality. Often, you must sacrifice one for the other, but it is possible to find the correct balance for you and the demands you place on your system.

There are several ways to optimize the video on your computer. The easiest way is simply to upgrade your video drivers. In many cases, the manufacturer will release new drivers for a particular card in order take advantage of certain features or to work with specific programs or operating systems. Windows 95 comes with many stock video drivers, but these are old, and if possible, you should upgrade to the latest driver directly from the manufacturer.

When shopping for drivers, get the latest that are programmed for your particular video card. This ensures you get the most out of your card's capabilities. The best way to get drivers is to go to the web site of the manufacturer, download them, and follow the instructions to set them up. Many systems, though, have a no-brand card, one that is not a name-brand. In these cases, look at the maker of the video chipset, often Trident, S3, or Cirrus.

Adjusting your video settings can help increase performance. For example, high resolutions have the ability to show more screen area, thus having more windows open and seeing more stuff in general. But, a larger resolution, on slower systems, can be a drag on overall performance, plus it reduces the number of colors your video card can display. The number of colors, similarly, can be a drawback. More colors increase image quality, but can be a performance lag. It also decreases available resolutions.

Changing your video settings is pretty easy. Many name-brand video cards come with their own program to adjust the settings. You can use this. Or, go to Control Panel, click on Display, Settings tab, then you can adjust them there.

Besides this, if you're within a certain memory range, say 1MB or video RAM on a 64-bit video card, increasing the memory to 2MB will help performance. This simply because 1MB only allows it to be 32-bit, but 2MB allows it to take the full 64-bit advantage. Other than this, adding memory to the card will not significantly increase video performance.

Computer Basics Page 5