AMD K6 Review

by Anand Lal Shimpi on April 3, 1997 4:51 PM EST

AMD had a knockout on their hands with the K5, unfortunately manufacturing problems and lagging delays kept them from grabbing a significant amount of the market. By the time the K5 was performing up to speed Intel had already announced and released their much faster Pentium MMX series of processors and Cyrix was already working on a successor to the 6x86. AMD's answer? A high powered yet low cost alternative to Intel's Pentium Pro and Pentium II, otherwise known as the K6.

The K6's main advantages include:

  • A highly advanced RISC86 core which decodes complex instructions into much smaller RISC86 operations for greater performance
  • 64KB of L1 Cache
  • 8.8 Million transistors piled up on a die 162 mm2 die using IBM's patented "flip-chip" technology
  • The smallest 6th generation processor out today!
  • High scalability from .30 micron fab process to a .25 micron fab process for use with upcoming K6 processors
  • Excellent price to performance ratio when compared to slower and more expensive Intel processors
First Generation AMD K6 Series Microprocessor
Chip Name P-Rating Clock Speed Bus Speed x Multiplier
AMD K6-PR2/166 PR2/166 166MHz 66 MHz x 2.5
AMD K6-PR2/200 PR2/200 200MHz 66 MHz x 3.0
AMD K6-233 N/A 233MHz 66 MHz x 3.5

After its introduction in April, AMD quickly dropped the PR2 rating of the K6 in favor of actual clock speed ratings.  An intelligent decision on AMD's part, since the PR2 ratings were confusing to many interested in the K6.

Under Windows 95, the performance of the K6 is nearly identical to Intel's more expensive Pentium II. The major differences between the K6 and the Pentium II are its FPU performance and 32 bit Windows NT performance. If neither of those matter to you (I should mention here that the K6's FPU is very well made, and extremely fast contrary to popular belief) then the AMD K6 is a superb choice for a microprocessor. What does the future hold for the K6? Lets take a look at some of AMD's future plans...

AMD K6 266 (a.k.a. AMD K6+)

This bad-boy will be AMD's successor to their first generation K6 processor, although it has been referred to as the AMD K6+ for some time now, the K6-266 will be a normal AMD K6 with a few interesting improvements on the original design.  The FPU of the K6-266 won't be a pipelined FPU, contrary to popular belief, however AMD has made some improvements to the K6's core which will result in faster FPU performance overall.  Currently, the K6's FPU isn't as great as it could be however it is in no way a "poor" FPU.  The Winbench98 FPUMark scores indicate that the AMD K6 isn't nearly as fast as the Pentium MMX in Floating Point operations, however if your main use for a computer is business applications with a few FPU intensive applications/games on the side the AMD K6 is still an excellent processor.

The AMD K6-266 will not be the power consuming daemon its predecessors were, requiring a core voltage of ~2.5v and producing a mere 8W of heat the K6-266 will be a prime candidate for mobile systems as well as desktops.  Expect some nice overclocking options with the K6-266, especially when coupled with the 83.3MHz bus speed setting found on some of the most stable Socket-7 motherboards.


AMD has decided to take the proprietary route with the K6 in the first half of 1998 with the introduction of the K6-3D.  The K6-3D will essentially be a K6, with a few new features, such as a proprietary set of 3D instructions designed to aid in speeding up 3D geometry calculations.  Unfortunately these instructions will be rivaled by Intel's MMX2 instruction set as well as Cyrix's own set of 3D functions, meaning that unless a standard is adopted by all of the manufacturers, both hardware and software, these instructions will remain un-used...much like our current set of MMX instructions.

Along with the addition of a proprietary set of 3D instructions, the K6-3D will be the first Socket-7 processor to embrace a 100MHz bus speed officially, and likewise will be introduced with a minimum clock speed of 300MHz.   Naturally, the K6-3D, although maintaining full compatibility with the Socket-7 specification, will require a new motherboard with support for the 100MHz bus speed in order to achieve its full performance potential.  It may be possible, although not very intelligent, to run the K6-300 at 66 x 4.5 provided that AMD does built in support for the 4.5x clkmul internally on the K6-3D, however with the K6-3D expect your next motherboard purchase to be based on a non-Intel chipset since Intel still refuses to support any bus speeds greater than the good 'ole 66MHz setting we've put up with for the past 2 years.

Physically the AMD K6-3D will feature a total of 9.3 million transistors, on a die size approximately 81 square mm.  Whether or not AMD will continue to use IBM's Flip-Chip technology with future K6 processors, including the K6-3D, is unknown however it would seem very unlikely that AMD would completely discontinue their current manufacturing methods in favor of a new procedure, especially this late into the year.  The manufacturing process which will be used to implement the K6-3D will of course, be a 0.25 micron process like Intel's new Tillamook processor as well as their upcoming additions to the Pentium II series.

AMD K6+ 3D

In order to take some of the lime light away from Intel when they release their long awaited successor to the Pentium Pro, the Deschutes, AMD will be releasing a Deschutes of their own in a sense.  In the late Third Quarter of 1998, AMD will be introducing the product of most of their efforts, the AMD K6+ 3D (what is it with companies and 3D these days?) The AMD K6+ 3D will feature all of the goodies the K6-3D will, as well as some "Pro-like" features which should have Intel shaking. Why?

AMD will supposedly introduce the K6+ 3D, with a full 256KB of 4 way set associative L2 cache, ON CHIP, running AT clock speed.  

The K6+ 3D will also feature an optional Level 3 Cache (L3) commonly found in high end processors such as Digital's 21264, commonly known as the Alpha. The actual size of the L3 cache has yet to be determined, however expect it to be in the range of 1MB - 8MB in order to stay competitive with the market's demands and Intel's offerings with their Deschutes.  The L1 cache size of the K6-3D and the K6+ 3D will most likely be at least 128KB, with the possibility of it being as great as 256KB although more than 256KB of L1 cache will quickly become a manufacturing limitation and will eventually drive the cost of the processor beyond what most are willing to pay for a non-Intel solution.   The K6+ 3D's die size, somewhat larger due to the L2 cache, of 135 square mm will house a whopping 21.3 million transistors.  I wouldn't become too happy about that number since the 21.3 million transistors include those required for the onboard L2 cache and not the processor exclusively.

Marketing 101

AMD's marketing angle for the K6-266, K6-3D, and K6+ 3D will be their price to performance ratio.  If AMD can deliver the chips the market demands, on time, and in great quantities at an affordable cost, they will gain the 30% of the market they are looking for.  However, if AMD is plagued once again by distribution problems, and if the price of the next generation K6 chips isn't what the market is willing to pay for a low cost alternative, then Intel will once again cast their dark shadow over the microprocessor industry.

1998 will be the year for competition, most of which Intel plans to eliminate with the introduction of their 64-bit masterpiece, the Merced a year later in '99.  AMD will continue to pursue their high goals even after the K6 processor dies out, especially with the rumored compatibility between Slot-1 and AMD's upcoming K7 to be released in 1999.

AMD K6 Performance

The following tests were conducted using the same configuration used in all AMD K6 motherboard tests, and can be found on the Socket-7 Motherboard Comparison Guide from which these scores were extracted.  Expect more scores to be up later this week, including a full set of Business Winstone 98 scores.

Windows 95 Performance of the AMD K6
Chip Business Winstone 97
K6-166 (66MHz x 2.5) 52.1
K6-188 (75MHz x 2.5) Not Run
K6-200 (66MHz x 3.0) 54.5
K6-208 (83MHz x 2.5) 58.9
K6-225 (75MHz x 3.0) 57.5
K6-233 (66MHz x 3.5) 57.0
K6-250 (83MHz x 3.0) 59.9

The Business Application performance of the AMD K6 is outstanding, expect more scores in this category later, especially Business Winstone 98 scores which test multitasking/task switching capabilities, a feature not found in Winstone 97.

AMD K6 Performance
Chip FPU Mark CPU Mark32
K6-166 (66MHz x 2.5) 540 492
K6-188 (75MHz x 2.5) 606 554
K6-200 (66MHz x 3.0) 647 524
K6-208 (83MHz x 2.5) 673 609
K6-225 (75MHz x 3.0) 728 604
K6-233 (66MHz x 3.5) 753 558
K6-250 (83MHz x 3.0) 807 675

The performance of the AMD K6 under Windows 95 is excellent, however the FPU Mark scores are a bit low compared to Intel's Pentium MMX and Pentium II processors.

From these scores you can easily tell (or you will be able to tell) that the K6 is not the world's best Quake performer, however, when coupled with a Diamond Monster 3D, it isn't all that bad.  The 3D Winmark 98 scores indicate that the K6's 3D performance, which is very FPU intensive, is not as strong as that of the Pentium II, however it is very competitive when compared to the Pentium MMX.

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  • darkewaffle - Friday, October 22, 2010 - link

  • BOLt - Thursday, November 25, 2010 - link

    Second, I guess. Old article! Still high-quality writing, though.
  • tipoo - Tuesday, February 8, 2011 - link

    Throw these in Anandtech Bench, lol
  • seepranavg - Saturday, July 15, 2017 - link

    wow first ever article
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    Only 4 comments on AT’s first article?
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