By Marc Spiwak

Only about a year ago, a 128-bit graphics accelerator was something of a rarity. If you did get your hands on one, you had to have plenty of processing power to realize the benefits of the high-end graphics card. But now, a Pentium machine is the de facto standard, and fast graphics have become a necessity, not a luxury. I tested two of the newest high-performance graphics accelerators available, the STB Lightspeed 128 and the TwinTurbo 128P4 from Integrated Micro Solutions.

A 128-bit graphics accelerator can transfer huge amounts of display data between different parts of the card's circuitry. It can enhance a Pentium's 32-bit performance and get the information to the monitor fast so images will be displayed quickly and smoothly.

The two cards I tested take different approaches to speedy graphics acceleration.

The STB Lightspeed 128 is based on the Tseng ET6000 graphics controller chip. The chip accelerates 256 raster operations, including stretch, compress, rectangular, trapezoidal, transparent BLTs, aligned and nonaligned operations, YUV-to-RGB color space conversion, color expansion, area fill, vector line drawing and 64-color hardware cursor support. The integrated digital video engine allows for enhanced software MPEG I playback. The Lightspeed 128 also uses new multibank DRAM (MDRAM)-memory broken upinto multiple, individual banks, which allows data to be accessed with less latency-rather than VRAM or EDO RAM.

I tested a Lightspeed with 2MB of memory, but a 4MB version is also available. Perhaps the most affordable 128-bit card on the market, the Lightspeed has one limitation: It's a 2-D only accelerator. With the recent developments in, and imminent acceptance of, 3-D imaging, that limitation could prove to be significant.

The Plug-and-Play Lightspeed 128 can support a maximum 1024x768 resolution with 65,000 colors and an 85Hz refresh rate. (The 4MB version supports resolutions up to 1280x1024 and refresh rates up to 160Hz.)

I was very pleased with the Lightspeed 128's image quality, and performance tests indicated that the card accelerates 2-D images quite well. The Lightspeed provided good .AVI playback performance in any size window. Software-based MPEG playback was also very good in a small window, but was too jerky to watch in full-screen mode.

The STB Vision control panel software installed as easily as the card did. The Vision control panel lets you change resolution and refresh rate on the fly, and color depth with a reboot. Other useful features include a zoom function and a virtual desktop feature that lets you work with an image area larger than your monitor's screen.

Though familiar to Mac users, Integrated Micro Solutions (IMS) is the new kid in the PC arena. The TwinTurbo 128P4 is its first offering for PCs. In it, IMS uses its own accelerator chip, the TwinTurbo 128 Plus. The chip is a high-performance GUI accelerator for PCI-based machines. It contains two 64-bit data pipelines operating in parallel and an interleaved VRAM interface, and can also take advantage of PCI bus mastering.

I tested a 4MB TwinTurbo, which is also available with 2MB and 8MB of VRAM. The 4MB model can display at resolutions up to 1600x1200 in 65,000 colors with a 75Hz refresh rate. For true color (16.7 million colors) you'll have to stick to resolutions of 1280x1024 and lower, or opt for the 8MB version.

The TwinTurbo is a Plug-and-Play card, and it installed under Windows 95 with no problem. The software that comes with the card offers a functional, easy-to-use control panel, but it doesn't let you adjust the refresh rate-a feature that you'd expect from the software.

The TwinTurbo 128P4 fared somewhat better than the Lightspeed 128 in my performance tests. The card's .AVI playback was good overall, as was its software-based MPEG. MPEG playback was superior when viewed in a window, and full-screen playback was watchable at all resolutions. Few graphics accelerators offer better software MPEG playback than the TwinTurbo 128P4. But an accelerator this powerful is pricey-a TwinTurbo with 2MB costs about $150 more than a Lightspeed with the same memory.

Either of these cards delivers high-quality, high-speed graphics that should satisfy even the most demanding users. If you need a little more speed and have a few more bucks to spend, the TwinTurbo is the right choice. Judging by how well the IMS TwinTurbo 128P4 accelerated MPEG video to full-screen size compared to the STB card, the TwinTurbo would be my pick if multimedia were a paramount concern. However if you're willing to give up a little speed to save money, you can't go wrong with the Lightspeed 128.

--Info File--
STB Lightspeed 128
Price: $249
Pros: Price
Cons: 2-D acceleration only
Platforms: Windows 95, 3.1x, NT
STB Systems
888-234-8750, 214-234-8750
WinMag Box Score: 3

IMS TwinTurbo 128P4
Price: $599
Pros: Speed
Cons: Price
Platforms: Windows 95, 3.1x, NT
Integrated Micro Solutions
408-369-8282,
fax 408-369-0128
WinMag Box Score: 3.5