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1.1.1. |
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1.1.1. |
Windows 3.1 on a standard PC, even one with a 486 processor, can be tediously slow unless its graphics performance is accelerated in some way, either with a faster processor or a special add-on graphics card (or both). When heavy duty applications (eg Authorware Pofessional) are added to this, performance can verge on the unacceptable. For this reason, many manufacturers are now offering "Windows acceleration" as a feature of some of their products, which usually means that the machines are equipped with fast graphics cards (often these days based on the S3 processor) that handle screen re-draws and graphics movements with greater efficiency.
| Graphics acceleration is recommended for multimedia CBL. |
There are no universally accepted standards for graphics acceleration on PCs, with the result that some accelerator cards are likely to work better with your applications and add-ons than others. The cause of this variation is often the variable quality of the software drivers supplied with the cards rather than the cards themselves, so it is important to check these carefully before committing yourself.
Drivers vary considerably with respect to the range of resolutions and colour depths they support, and have a habit of throwing up problems when you least expect them. For example, some S3-based accelerators have a tendency to conflict with Authorware Professional applications, almost certainly because of inadequate drivers.
| Always check the software drivers that come with the graphics card you are considering, particularly with respect to resolution, colour depth and their effect on your favourite Windows applications. |
Enhanced graphics performance under Windows is commonly achieved these days by combining acceleration with Video Local Bus (VL-Bus), a bit of bypass surgery that enables the central processing unit (CPU) of the PC to circumvent the serious communications bottleneck imposed by the standard ISA (Industry Standard Architecture) expansion bus and talk to peripherals at something approaching optimum speed. This communications "fast lane" can greatly improve graphics-related activities (see section 6.1.1B).
| VL-Bus may be the solution for now if all you need is low cost Windows acceleration. But test the card you like with your applications. |
A number of VL-Bus solutions have been proposed, but only one is an accepted standard: VESA VL-Bus, a local bus architecture defined by the Video Electronic Standards Association (VESA). As a consequence, VESA VL-Bus is increasingly the flavour of local bus most frequently offered by PC manufacturers, though some manufacturers continue to offer their own proprietary VL-Bus solutions. In the face of competition from Intel's own local bus architecture - PCI (see below) - the announcement of a VESA 2 VL-Bus standard is imminent. This is designed mainly for Pentium machines, embodies a 64-bit architecture and supports processor speeds of up to 150 MHz (see section 6.1.1B).
| If VL-Bus is the solution for you, go with VESA. But remember, VL-Bus is designed for 25 and 33 MHz machines (or doubled-up versions of them). It will therefore be unstable on 50 MHz systems. |
At the high end of graphics acceleration are boards such as Diamond's Viper VLB and Matrox's MGA Impression, but it is as well to remember that high end cards may not necessarily be the most suitable for your particular application. For example, our Authorware Benchmark, which tests the multimedia capabilities of PCs and Macs running Authorware Professional, tends to return higher scores on PCs with low-end rather than high-end graphics cards. The very opposite may of course be the case for other authoring systems.
Two other local bus architectures are on the way, one imminently, the other on the horizon: respectively Peripheral Component Interconnect (PCI) from Intel, widely acknowledged to be a better design solution to the ISA bottleneck problem than VL-Bus; and QuickRing from Apple, the most advanced of the three architectures and approximately three times faster than VL-Bus (see section 6.1.1). The first machines to support PCI are now on the market, but they are high end machines and likely to remain so for at least a year. Also, PCI is still buggy and unstable. Apple has announced support for PCI despite the superiority of its own solution, so it may well be that PCI and QuickRing will eventually co-exist on the PowerPC Macs.
| PCI is a better design solution if you can afford the price premium. But don't rush in until it is a proven technology in your own applictaion area. |
Whatever graphics enhancement solution you opt for, watch out for incompatibility problems. Local bus architectures, for example, are incompatible with Intel's ActionMedia II digital video adapter. Intel has designed a three-way adapter cable that enables local bus machines to work with ActionMedia boards, but it is expensive (enquiries to Multiteq).
This fix also circumvents another ActionMedia II problem, namely its inability to work with video cards set at more than 256 colours. If local bus proves to be a problem in compatibility terms, it may be possible to revert to conventional ISA connections to circumvent the problem. However, all local bus graphics enhancements will be lost by doing this.
| VL-Bus can significantly improve Windows performance, but is too new to have revealed all its incompatibility potential, especially in multimedia machines. Be sure to test for compatibility with your essential devices. |
This is the newest of the expansion bus standards, and specifically addresses multimedia - ie the problem of moving large digital audio and video files around the PC without subverting performance (see section 6.1.1.E).