Up To 32 MB Of Onboard Memory At Clock Speeds Of Way Over 100 MHz
The onboard memory of each 3D-card has a very high impact on the overall 3D-performance. 16 MB is enough to run 3D applications at up to 1024x768 in 32 bit color depth (this is not valid for PVRSG, which needs less memory for that). Realistic 3D scenes at 1280x1024x32 bit color require 32 MB and that's what is state-of-the-art today. The memory clock still varies a lot between the different chips and so does the width of the memory interface, where currently 128 bit is state-of-the-art, moving towards 'dual-256 bit' = 2 interfaces with 128 bit or real 256 bit soon. The graphics memory bandwidth is an important limiting factor of the 3D-performance and you can say that a vendor who can safely handle highest memory clocks is well prepared for future developments.
More and more games are offering a true-color mode due to quality reasons, meaning that the displayed frames are using a 24 bit deep color depth (RGB, 16.7 million colors). This means that a huge amount of data needs to be computed for each frame, but the performance of the latest 3D-chips is starting to be capable of supplying this kind of computing power. A 3D-architecture that is limited to only 16 bit, as in case of the Voodoo3 requires a reduction of color information and is thus decreasing the quality and reality level. 32-bit color rendering with 32-bit Z-buffering will stay the optimal implementation for quite some time to come.
Fast RAMDACs With At Least 250 MHz Or Digital Flat Panel Support
The RAMDAC is the link between the digital display information stored in the frame buffer and the analog CRT. The higher the bandwidth of the RAMDAC, the higher is the number of pixels that can be displayed on the CRT each second. This means that a faster RAMDAC is crucial for decent refresh rates, its quality is crucial for the quality of the displayed picture on the screen and only fast RAMDACs can supply really high resolutions of more than 2000x1500, which is most important for 2D applications. If the user prefers a flat panel screen, he should make sure that there is no digital-analog-converter (DAC) and then a analog-digital-converter (ADC) between the graphics memory (or frame buffer) and the flat panel, because it is not only a waste of silicon, but it also decreases the display quality by a serious amount. A flat panel requires digital data and should thus be supplied with nothing else than that. That requires a digital output of the graphics card, where DFP is one of the standards. For optimal 2D-quality you should therefore either look for a fast RAMDAC for a CRT or a digital output for a flat screen.
AGP vs. PCI is a question that doesn't need to be asked anymore today. AGP has succeeded in the upper performance area quite a while ago already. When AGP 4x will be released later on this year, we may finally see the visible advantage that many of us are still missing. A today's 3D-card should support AGP 2x to be at least able to handle the data bandwidth that's required for 'several million polygons/s'. Games with large textures are coming up, FlightSim 99 is only one example, so that the 3D-chip should also be able to do AGP-texturing, which is one of the things that Voodoo3 is not able to do.