PREFACE:
The video card converts the digital image information generated by the operating system or application to an analog signal that is provided to the monitor. Six primary factors are weighed in the selection of a video card, RESOLUTION, COLOR DEPTH, VESA COMPLIANCE, VESA COMPATIBILITY, EMERGING STANDARDS, 3D and PERFORMANCE.
RESOLUTION:
The size of the monitor is usually selected based on a trade-off between cost and size. Larger monitors can display more useable horizontal and vertical pixels (resolution) which translates into more useable, visible information without scrolling. The larger the monitor, the higher the cost. A 14" monitor can adequately display 640X480 pixels, a 15" can adequately display 800X600 pixels, a 17" can adequately display 1024X768 pixels, and 20" or larger can adequately display 2048X1024 pixels. Running a 14" monitor at 2048X1024 pixels results in text and icons being so small and jagged that the image is unreadable and therefore unusable.
COLOR DEPTH:
COLOR DEPTH refers to how many colors can be represented on the monitor. TRUE COLOR refers to 24 bits per pixel (bpp). 24bpp represents 14.7 million different colors, more than the human eye is capable of resolving. There has been a recent move to replace 24bpp with 30bpp as the definition of TRUE COLOR. HIGH COLOR refers to 16 bpp which translates into 64000 colors. 8bpp provides for VGA (Video Graphics Adapter) compliance of 256 colors along with 640X480 pixels. 4bpp provides for CGA or MGA compliance of 16 colors. Super VGA (SVGA) refers to anything above 640X480 pixels or 256 colors. TRUE COLOR either 24bpp or 30bpp is the most common and recommended supportable color depth.
VESA COMPLIANCE:
The combination of color depth and resolution determine the minimum performance measures for both the monitor and graphics adapter card. This video information has to be displayed in such a manner as to be flicker free to avoid eye strain headaches. the Video Electronics Standard of America (VESA) provides a compatibility standard for both the monitor and the video card. The VESA standard calls for a Horizontal Scan Frequency of no less than 70Hz non-Interlaced. The Horizontal Scan Frequency is a measure of how many times per second the entire screen is redrawn. A technique called Interlacing effectively halves the entire screen redraw rate by redrawing odd numbered rows on one pass and then even numbered rows on the next. A monitor and graphics card manufacturer can claim to be VESA compatible and can claim to support a very impressive maximum resolution and can claim to support a very impressive maximum Horizontal Scan Frequency all in the same advertisement without specifically saying it supports all those maximums together at once. E.G. a 15" monitor can be advertised to be VESA compliant, has a maximum resolution of 2048X1024 pixels and has a maximum Horizontal Scan Frequency of 80Hz but that does not mean that the monitor provides the maximum 80Hz Horizontal Scan Frequency at the maximum 2048X1024 resolution, so read the ad carefully and specifically ask before buying either the monitor or the video graphics adapter card.
VESA COMPATIBILITY:
Since SVGA covers such a broad range of resolution and color depth, VESA devised a scheme of screen modes. Programmers utilize these screen modes in the development of their products. There is VESA 1 and VESA 2.0 compatibility modes. Most video graphics adapter card manufacturers develop drivers for the major operating systems such as Microsoft Windows. Game developers typically use VESA 2.0 for DOS based games. Not all video cards support VESA 2.0 100%. The VESA standard may be supplanted or updated by the new MMX technology being produce by Intel in their new CPU designs.
EMERGING 3D STANDARDS:
If you are using Microsoft Windows 95 or later, DirectX is becoming more an issue. WIN95 game developers are producing games that use DirectX 1.0, 2.0, and 3.0. The video card manufacturers are scurrying to catch up and write drivers for their products to support these standards. DirectX refers to a whole list of issues including input devices and sound cards as well as video cards. But in the video graphics area, DirectX also includes DirectDraw and Direct3D. Before DirectX video card manufacturers developed drivers and their hardware around obscure Microsoft Windows based functions, not standards. The result was an endless trail of driver updates, bugs, and video card vendors maximizing their products to get the best Windows performance scores. Game developers could not expend the programming expertise to develop drivers for each and every video card manufacturer and the video card manufacturers could not expend the resources to develop drivers for each and every game developer. Instead, each video card manufacturer wanted their own proprietary scheme to be the standard and thereby clinching the entire market. Microsoft, Intel, and VESA have tried and are continuing to try to establish a standard for both the video card manufacturers and the game developers. Intel's approach is interesting. For years, game developers relied on using CPU based graphics routines to avoid the graphics card industries. Performance of their games could only be enhanced by processor upgrades. Microsoft and Intel both want to move away from the old 16bit based operating environment to the new 32 or 64 bit environment, but that means ending the backward compatibility trail. What Microsoft and Intel are both yearning for is that video card manufacturers and application and game developers will start using DirectX and MMX standards. Intel wants to sell more processors, Microsoft wants to sell more copies of operating systems, they both have a mutual interest in this area. Even with the emerging 3D technology and market focus, I believe that application and game developers will ultimately migrate to DirectX and MMX. This will force the video graphics adapter market to design their products to excel in DirectX and offload the functions provided by MMX to the CPU. I believe both of these emerging standards is inevitable, and good for the consumers. I for one am tired of the video graphics card adapter manufacturers causing me problems in their greed to be the only one left standing. In a way, the decision has been made for them, instead of every manufacturer having a low, medium and high range card, I think we will see a trend to certain manufacturers wanting to capture the high end market and others that want to capture the mid and low end market. We have already begun to see this. The rate at which this will occur depends on Microsoft and Intel continuing to pour efforts into this area.
PERFORMANCE:
The primary components on the video card that do these things are the video card BIOS, video card processor, video card memory, and RAMDAC. This product has a combined video card processor and RAMDAC.
The video card BIOS supplies the compatibility modes. A video card that requires the loading of a Terminate and Stay Resident (TSR) program will not perform as well as a card that has the modes in the video card BIOS which is used by the video card processor. Meaning that the CPU has to process the TSR before the video card processor can process the data. The video card processor can use the video card BIOS directly independent of the CPU.
The video card processor can offload video functions from the CPU and thereby "accelerate" the graphics output or screen drawing including 3D effects. The amount of processor power required is determined by the amount of data that needs to be processed which is affected by Color Depth, Resolution, and Horizontal Scan Frequency as well as 3D effects.
The video card processor needs it's own memory to process data just like the CPU on the motherboard needs RAM. This same RAM is used to hold the information for the RAMDAC to convert and subsequently provide to the monitor for displaying. Since RAM has dropped radically in price, video cards that used to cost $400 are now available for $200. The amount of memory that a video card needs depends on the resolution and color depth. If you intended to purchase a 17" monitor, you will want to run 24bpp TRUE COLOR at 1024X768 pixels which translates into you buying a video card with 4MB of RAM. A 15" monitor running at TRUE COLOR and 800X600 means you need 2MB of RAM. Two primary types of RAM are being used on video cards, EDO and VRAM. VRAM cards are still more expensive and still are faster.
The RAM Digital to Analog Converter (RAMDAC) takes the digital screen data in the RAM and converts it into an analog signal to be provided to the monitor. The speed with which the RAMDAC does this will determine the Horizontal Scan Frequency. The resolution and color depth determine how much information needs to be converted along with a 70Hz VESA Horizontal Scan Frequency determines how fast the RAMDAC needs to be. Typically this is specified in a measure of Bandwidth as is the monitor, a value of 200MHz or more is required.
Wrapping this all up, the speed with which a graphics adapter card can send the compatible information to the compliant monitor is what separates low end and high end cards.
3D standards include Microsoft Directx, OpenGL and Glide. All other symbols you hear about are trademark items, not universal standards. These include 3dfx, RIVA, TNT, etc. The different video card companies are all trying to corner the market with their own proprietary 'standard'. The one that has come closest to accomplishing this is 3dfx. But 3dfx was bought out. Don't let that deter you from buying a 3D card though. I have bought ATI and 3dfx cards and have thoroughly enjoyed them. Whatever you buy, just make sure it supports Directx.
