28 Will my video speed up enormously with a VLB/PCI upgrade?
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This article is from the comp.sys.ibm.pc.hardware.video Frequently Asked Questions, by Michael Scott with numerous contributions by others. (v1.0).
28 Will my video speed up enormously with a VLB/PCI upgrade?
This is another question which can be answered by "it depends on your application". If you require high bandwidth on your system bus because of intensive video demands, then VLB (for 486's) or PCI (for Pentium/586's) is a must. Examples of high bandwidth applications include most VGA (sometimes incorrectly called DOS) games, full-motion video or other VGA-intensive operation.
You may think that a pseudo-OS like Windows 3.1 would require a video card with high VGA speed, but that isn't necessarily the case. The problem with VGA is that almost all of the work must be done by the CPU. This, coupled with the fact that each refreshed pixel must be transported across the system bus means that VGA is slow for OS's like Windows or OS/2. Fortunately many operations in GUI environments (like move a window, for example) can be implemented right on the video card, and are handled by the video coprocessor rather than the system CPU. This reduces both the time required to complete such tasks and the amount of data that has to flow over the system bus. An implementation like this is often called video acceleration (see "How does a video accelerator work, and will one help me?").
With this background, we can now see that most general operations within a GUI environment can be handled right on the video card. As a result, it's possible to have a card that is fast for Windows operations, but runs on the ISA bus. In fact, for most operations, it's quite possible that the ISA-based card will respond just as quickly as an equivalent VLB or PCI card.
To summarize, high-bandwidth applications like full motion video or VGA games will benefit from a fast bus like VLB or PCI. For most GUI operations (like in Windows 3.1, Windows 95, OS/2, XFree86, etc) an accelerated ISA card might be the most economical upgrade path.
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