AMD's K6-2 Challenges Intel for 3D

by Alan Zisman (c) 1998. First published in Canadian Computer Wholesaler, August 1998

Ironically, at almost the same time that the US government announced that it was investigating chipmaker Intel for monopoly practices, one of Intel competitors announced its latest and greatest CPU.

Advanced Micro Devices (AMD? officially announced its K6-2 processor at Atlanta?s Electronic Entertainment Expo, releasing 300 and 333 MHz models, with plans to boost performance to 350 and eventually 400 MHz in the third and fourth quarters of the year. (Intel Pentium IIs already available running at 400 MHz). The new product line features a number of enhancements in addition to raw CPU speed.

This chip marks the first time that one of Intel?s competitors has gone beyond simply cloning the feature set of an existing Intel product. The K6-2 is the first chip to offer 3DNow!, a set of multimedia and 3D enhancements that go well beyond the MMX instructions offered by Intel and current clone-chips. "For the first time, AMD has introduced a processor that is differentiated not solely by megahertz or price but by innovative technology that delivers a new level of 3D performance and realism," said S. Atiq Raza, AMD executive vice president and chief technical officer. The 3DNow! instructions will also be available in upcoming chips from Cyrus and Centaur, as well as AMD.

While Intel is working on a similar set of 3D instructions, they will not be compatible with 3DNow!. The result is a window of opportunity for Intel?s competitors, where they will be offering products that are, in this way, at least, more advanced than Intel?s offerings. But there is a catch?3DNow!, like MMX, only provides improved performance in software that is written to take advantage of it. Microsoft has promised support for 3DNow! in their next-generation, DirectX 6.0; as a result, any programs (primarily games) written to use DirectX 6.0 will automatically provide 3DNow! support. Software written to take advantage of the OpenGL 1.2 and 3DFx Glide programming specifications will also support 3DNow!.

3DNow! offers 21 new processor instructions, characterized as Single Instruction Multiple Data, directed at speeding up the interaction between the CPU and a 3D accelerator card, and promising to deliver up to four floating point instructions per clock cycle.

In addition, the K6-2 will, like the newest Pentium-II offerings, support motherboards running at 100 MHz bus speeds. This results in increased performance across the board, not just for CPU-intensive tasks. (Note, however, that best performance at 100 MHz, regardless of the CPU, requires faster RAM, which is currently more expensive that RAM that only has to keep up with 66 MHz motherboards). Expect performance increases of 15% or more, moving to a 100 MHz motherboard.

Like its predecessors from AMD and the other Intel competitors, the K6-2 relies on the Pentium-style Socket 7 design, but the new product will require an updated version, known as the Super7 Platform. Along with the high-speed bus, Super7 designs will support AGP graphics adapters, until now, only available on designs based on Intel?s Slot 1 for Pentium-II and Celeron processors.

Despite the enhancements, AMD?s product continues to lag behind Intel?s Pentium-II line in a number of ways. While AMD claims the K6-2 benchmarks as much as four times as fast as a P-II in 3D-intensive operations (with properly written software), and while its integer instructions (used in typical business software) are comparable to the P-II?s, the K6-2 remains inferior to the P-II line in running standard floating point instructions, lagging behind by as much as 50% on standard benchmark tests.

As a result, many popular games that have not been written to take advantage of the K6-2?s new instructions will run better using Intel iron. Even Intel?s low-priced Celeron offers all the floating point power of a full P-II (as was pointed out to me by reader Art Prufer).

And while, given a 100 MHz bus (and high-speed RAM), systems built around either a P-II or a K6-2 will access memory at full bus speed, a Pentium-II has the advantage in the speed that it accesses its L2 cache. With the cache built onto the P-II?s cartridge, it is accessed at half the processor speed?175 MHz for a 350 MHz processor. On K6-2 systems, the cache is on the motherboard, and is accessed at the motherboard?s speed?100 MHz regardless of the processor speed. In many cases, the difference in cache speed will result in a noticeable difference in overall system performance.

Recently, a shootout was set up between similarly priced K6-2 and P-II systems, comparing performance on a number of cutting edge games. (

Rather than comparing systems with the same speed processors and motherboards, the test team put a 333 MHz K6-2 on a 100 MHz motherboard up against a 300 MHz P-II in a 66 MHz motherboard?this enabled them to compare systems that were roughly at the same price-point. (The 100 MHz BX motherboard required for the higher-speed P-II systems costs about twice as much as the 66 MHz LX boards, which are about the same price as the Super7 motherboards). They used pre-release versions of DirectX 6 and tested games such as the upcoming Quake2, offering 3DNow! Support, as well as others that lacked such support.

Their results? About 10% better performance for the K6-2 when running games (such as Quake2) offering direct support for its features. When software support was not built into the game, however, 3DNow!, still provided the K6-2 more or less parity with the Intel system, evidence of the effects of DirectX 6.

AMD believes that it has overcome the production difficulties that have sometimes limited supplies of its processors; all K6-2s are being produced at on .25 micron wafers, offering increased yield.

Looking for still more evidence that the market has opened up more fully for Intel?s competitors? With HP?s announcement that it will ship AMD CPUs in some of its Pavillion-series computers, virtually all of the major brand name computer manufacturers offer one of the non-Intel processors in at least part of their product lines.

And with the K6-2 as the first non-Intel 80x86-type CPU to go beyond Intel?s feature set, there?s evidence that the one-time cloners are no longer contents to stay a generation behind Intel, aiming for the bottom-end of the market.

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Alan Zisman is a Vancouver educator, writer, and computer specialist. He can be reached at E-mail Alan