AMD K6-2

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AMD K6-2 logo
Production: 1998 to 2000?
Producer: AMD
Processor clock: 266 MHz to 550 MHz
FSB cycle: 66 MHz to 100 MHz
L1 cache size: 64 KiB
Instruction set : x86
Base: Super socket 7
Names of the processor cores:
  • Chomper
  • Chomper-XT
Mobile version of the AMD K6-2.

The K6-2 is an x86 - microprocessor from AMD , the clock speeds from 233 to 550  MHz was produced. It has a 64 KiB level 1 cache (32 KiB each for data and instructions), requires 2.2  volts of operating voltage and was manufactured using a 0.25 micrometer process. It has 9.3 million transistors and uses a socket 7 or super socket 7 to connect to the motherboard . The K6-2 is a further development of the K6 .

The K6-2 and its competition

The K6-2 was positioned as a competitor to the slightly older and much more expensive Intel Pentium II . The performance of the two CPUs is similar: While the K6-2 runs faster for general tasks, the Intel CPU is clearly superior for floating point calculations. The K6-2 was a very successful CPU that gave AMD the notoriety and financial stability to launch the Athlon .

The K6-2 is the first CPU with a floating point SIMD instruction set ( 3DNow! ), Which in theory can significantly improve the performance of 3D applications. AMD had this technology on the market for several months when Intel followed suit with the similar but more complicated iSSE instruction set.

Almost all K6-2s are designed for operation at 100 MHz FSB and thus for Super Socket 7 motherboards, which at the time brought a significant improvement in system performance. At the beginning of the K6-2 line, the K6-2 / 300 was the best-selling variant. It quickly earned AMD an excellent reputation in the marketplace and competed fiercely with Intel's Celeron 300A . This one has a smaller but faster L2 cache and a more powerful floating point unit; the K6-2 offers faster main memory access (thanks to Super Socket 7) and the 3DNow! command extensions. Both processors sold well and were able to attract loyal buyers (at the time the fastest Pentium II available was slightly faster than these two processors, but at a much higher price).

AMD later built a number of faster K6-2s, with the 350, 400, 450 and 500 MHz variants being the most successful. At the time of the 450 and 500 MHz models, newer and faster chips had already taken over the high-performance market, while the K6-2 was still competing with the Celerons, but only in the class of cheap CPUs. The 100 MHz fast front side bus allowed the K6-2 to keep up with the much higher clocked competition for a long time.

The versions with the Chomper XT core were particularly popular with overclockers and those willing to upgrade. These are usually quite easy to overclock and with older motherboards that do not support multipliers above 3.5 ×, the fact that the Chomper XT interprets a set 2 × multiplier as 6 × proves to be beneficial. There are also special CPU adapter sockets that adjust the voltage and multiplier so that e.g. B. a K6-2 / 400 in Pentium 1 motherboards with socket 7 at 66 MHz FSB and the multiplier 6 run. On the front of the CPU there is a number in the lower left corner of the ceramic housing. Processors with a Chomper XT core have the number 26351, processors with a Chomper core have the number 26050.

The little-known K6-2 + is actually not a K6-2 at all, but an extended version of the AMD K6-III for laptops.

The CPUs of the AMD K6-2 series with a speed of 350 MHz or more are not compatible with Windows 95 without a patch because a time loop is implemented in the Windows 95 driver IOS.VXD, which increases due to the high speed of the processor is processed quickly and then divides by zero. The patch was developed by Microsoft and AMD and was available from AMD on the homepage. To execute the patch, the CPU has to be clocked below 350 MHz, in practice mostly at 300 MHz. After the patch has been executed, the CPU can be clocked up to its nominal clock again, so that full performance can be used. Starting with Windows 98 , this patch was no longer required, and higher-clocked K6-2s were supported from the start.


AMD K6-2 architecture block diagram

In retrospect, the K6 and its derivatives were a double-edged sword for AMD in terms of performance. Due to its slow floating point unit (because it does not have a pipeline ), the K6 does not stand a chance against its direct competitors, the Intel processors Pentium MMX and Pentium II , in FPU-heavy applications such as the then emerging 3D games. In addition, the Pentium II could access the fast L2 cache directly on the processor module, while the processors of the K6 and K6-2 series still used the L2 cache of the (super) Socket 7 mainboard. This bandwidth disadvantage made to create the AMD CPUs, only the K6-III and the mobile versions K6-2 + and K6-III + ran at the end of K6 era thanks to the The integrated Level 2 cache to top form. These clearly show the advantages of the K6 architecture: A fast integer unit with a very short pipeline, an intelligent branch prediction unit and a translation lookaside buffer that was very large for the time, gave it a high level of efficiency ( instructions per cycle ). In a test against the successor architecture K7 with the same clock frequency, the K6-2 + emerged as the winner in many integer-heavy benchmarks. But while the only six-stage integer pipeline made the K6 design largely independent of software optimizations, on the other hand, this low-latency design significantly limited the maximum clock frequency: the K6 architecture reached its maximum at 570 MHz, while the successor K7 design over-scaled the years to well over 2 GHz.

Model data

K6-3D (chomper)

K6-2 with 300 MHz (chomper)
  • CPUID: Family 5, Model 8, Stepping 0
  • L1 cache: 32 + 32 KiB (data + instructions)
  • MMX , 3DNow!
  • Super socket 7 with 66 and 100 MHz
  • Operating voltage (VCore): 2.2 - 2.4 V.
  • Release DATE: May 28, 1998
  • Manufacturing technology: 0.25 µm
  • The size: 81 mm² with 9.3 million transistors
  • Clock rates (power consumption):
    • 233 MHz (13.50 W)
    • 266 MHz [28. May 1998] (14.70 W)
    • 300 MHz [28. May 1998] (17.20 W)
    • 333 MHz [28. May 1998] (19.00 W)
    • 350 MHz [27. August 1998] (19.95 W)

K6-3D (Chomper-XT)

K6-2 with 533 MHz (Chomper-XT)

Has the improved CPU core of the K6-III , but without a level 2 cache.

  • CPUID: Family 5, Model 8, Stepping 12
  • L1 cache: 32 + 32 KiB (data + instructions)
  • MMX , 3DNow!
  • Super socket 7 with 66, 95, 97 and 100 MHz
  • Operating voltage (VCore): 2.2 - 2.4 V.
  • Release DATE: November 16, 1998
  • Manufacturing technology: 0.25 µm
  • The size: 81 mm² with 9.3 million transistors
  • Clock rates (power consumption):
    • 266 MHz
    • 300 MHz
    • 333 MHz
    • 350 MHz
    • 366 MHz [16. November 1998] (20.80 W)
    • 380 MHz [16. November 1998] (21.60 W)
    • 400 MHz [16. November 1998] (16.90 - 22.70 W)
    • 450 MHz [26. February 1999] (18.80 - 28.40 W)
    • 475 MHz [5th April 1999] (19.80 - 29.60 W)
    • 500 MHz [30. August 1999] (20.75 W)
    • 533 MHz [29. November 1999] (20.75 W)
    • 550 MHz [22nd February 2000] (25.00 W)

See also

Web links

Commons : AMD K6-2  - collection of pictures, videos and audio files

Individual evidence

  1. ^ Andreas Stiller: Architecture Contest - Design comparison: AMD K7 Athlon versus Pentium III ( English ) February 1, 1999. Archived from the original on September 27, 2008. Retrieved on February 2, 2013: “ Additionally AMD made a significant change [to the Athlon] compared to the K6-2. After the disaster with the much to fast loop instruction it was slowed down to the sleeping pill level of the Pentium-II. Sloppily programmed software with naïve time loops (like Windows 95 uses for example) could not deal with such fast loops - and of course the user blamed the processor. Instead one should have blamed Microsoft ... "
  2. Andreas Stiller: INSPECTION . In: c't . No. 18 . Heise-Verlag, 1999, p. 154 ff . ( Fee-based download of the journal article , backup in the Internet Archive ( Memento from January 12, 2009 in the Internet Archive ) [accessed on January 12, 2009] Performance comparison of various CPUs, including K6-2 and K6-III with the same clock frequency).
  3. Nero24: AMD K6-2 + against AMD Duron - meeting of the generations. Planet 3DNow !, December 6, 2000, accessed October 19, 2011 .