MONITOR INTERFACE
Most graphics adapters provide a single vi
deo connection based on the standard D-shell, 15-pin VGA connector. Some high-end boards offer RGB (i.e., BNC) connectors. Some boards have multiple active video connectors, allowing multiple monitor attachments.
GRAPHICS ACCELERATOR
Provides low-level graphics operations. A 64-bit chip can transfer data in and out of its internal frame buffer 64 bits at a time. DRAM, VRAM, and the local bus accept only 32 bits of data at a time. A 32-bit interleaved architecture prepares one bank of memory while transferring to a second bank, reducing the transfer to a single clock cycle. Look for 64- or 32-bit interleaved architectures.
VIDEO MEMORY
VRAM-based boards have the reputation of being dramatically faster than DRAM-based boards, but DRAM designs have improved to the point where they're not much slower. Choose DRAM for economy if you mainly operate in 1024- by 768-pixel resolution with 256 colors. VRAM is a must for refresh rates that provide clear im
ages at higher resolutions and color levels.
BUS INTERFACE
We tested only PCI and NuBus adapters in this review. PCI's throughput is better than that of ISA and EISA; in addition, with its flexibility and ease of use, it's becoming the local-bus standard. For Macintosh systems, NuBus is the current accepted standard; it has been self-configuring for years.
VIDEO BIOS
At start-up, your system looks to the video BIOS (i.e., ROM) for the start-up code that identifies the graphics card and its software interrupt (which is almost always INT 10h) to control video actions. Sometimes the video BIOS is shadowed to system RAM for improved performance.
