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AMD K6-III
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The K6-III, code-named "Sharptooth", was an x86 microprocessor manufactured by AMD, which was the last and perhaps fastest of all Socket 7 desktop processors. It was released on February 22, 1999, with 400 and 450 MHz models.
For an extremely short time after its release, the fastest available desktop processor from Intel was the Pentium II 450 MHz. However, the K6-III also competed against the Pentium III "Katmai" line, released just days later on February 26.
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Encyclopedia
The K6-III, code-named "Sharptooth", was an x86 microprocessor manufactured by AMD, which was the last and perhaps fastest of all Socket 7 desktop processors. It was released on February 22, 1999, with 400 and 450 MHz models.
For an extremely short time after its release, the fastest available desktop processor from Intel was the Pentium II 450 MHz. However, the K6-III also competed against the Pentium III "Katmai" line, released just days later on February 26. "Katmai" CPUs reached speeds of 500 MHz, slightly faster than the K6-III 450 MHz. K6-III performance was significantly improved over the K6-2 due to the addition of an on-die L2 cache running at full clock speed. When equipped with a 1MB L3 cache (on the motherboard) the 400 and 450 MHz K6-IIIs is claimed by Ars Technica to often outperform the hugely higher-priced Pentium III "Katmai" 450- and 500-MHz models, respectively.
The K6-III 450 MHz is sometimes touted, especially on the internet, as the first AMD processor to out-perform the top model offering from Intel. However, this is a difficult claim to support, for two principal reasons: Firstly, although the official launch of the K6-III preceded that of the faster Pentium III, the date of actual market availability may have come slightly later; second, processor performance across architectures is not perfectly scalar, and so although the Pentium II 450 MHz performed slower in certain areas, it was faster in others.
Architecture
In conception, the design is simple: it was a K6-2 with on-die L2 cache. In execution, however, the design was not simple; with 21.4 million transistors, it was a very large chip to manufacture with early 1999 technology, and the K6 core design did not scale well past 500 MHz. Nevertheless, the K6-III 400 sold well, and the AMD K6-III 450 was clearly the fastest x86 chip on the market on introduction, comfortably outperforming AMD K6-2s and Intel Pentium IIs.
The K6-III implemented the x86 instruction set by translating x86 instructions into RISC86 operations internally and had separate multiplier and ALU for additional instructions to improve multimedia and 3D graphics performance. It also contained internal L1 cache with the full-speed L2 cache on the chip and could be supported by L3 cache on the ordinary motherboard.
Enhanced RISC86 microarchitecture
- two-level branch prediction
- speculative execution
- out-of-order execution
- dual instruction decoders, each decodes up to two x86 instructions per clock
- up to 6 RISC86 operations per clock
- 10 parallel specialized execution units, 6-stage pipelined
- register renaming and data forwarding
3DNow!
A single instruction multiple data (SIMD) operations by a packed single-precision floating-point data format. It was an enhancement to the MMX instruction set, which contained 21 new instructions that support SIMD floating-point operations and includes SIMD integer operations, data prefetch, and faster MMX-to-floating-point switching. The K6-III+ had the "Enhanced 3DNow!"(Extended 3DNow! or 3DNow+) which added 5 new DSP instructions, but not the 19 new extended MMX instructions.
TriLevel Cache
The original K6-2 had a 64 KiB primary cache and a much larger amount of motherboard-mounted cache (usually 512 KiB or 1024 KiB but varying depending on the choice of main board). In contrast the competing Intel parts used 32 KiB of primary cache and either 128 KiB of full-speed secondary cache integrated into the CPU itself (Celeron) or 512 KiB of half-speed cache mounted on a processor daughter board (Pentium II, Pentium III).
The K6-III, however, used both methods: it had 64 KiB primary cache, a 256 KiB on-chip full-speed secondary cache (similar to the Celeron-A's but twice the size), and the variable size motherboard mounted cache on the Socket 7 or Super7 main board became L3 cache, so called "TriLevel Cache". (up to 2 MB)
Market performance
Intel's Pentium II replacement was not yet available but, as a stop-gap, Intel introduced a modestly revised version of the Pentium II and re-badged it as the "Pentium III". The base design was unchanged (the addition of SSE instructions was at that time of no performance significance) but Intel's new production process allowed clockspeed improvements, and it became difficult to determine which company's part was the faster. Most industry observers regarded the Intel part as superior for floating-point intensive tasks (such as most 3D games), but the K6-III as better for mainstream integer work.
Both firms were keen to establish a clear lead, and both experienced manufacturing problems with their higher-frequency parts. AMD chose not to sell a 500 MHz or faster K6-III after the rare 500 MHz K6-III had been immediately recalled; it was found to be drawing enough current to damage some motherboards. AMD preferred to concentrate on their soon-to-be-released Athlon instead. Intel produced a 550 MHz Pentium III with some success but their 600 MHz version had reliability issues and was soon recalled.
With the release of the Athlon, the K6-III became something of an orphan. No longer a top-of-the-line CPU, it nevertheless required substantial manufacturing resources to produce: at 21.4 million transistors, it was almost as expensive to make a K6-III as a 22-million-transistor Athlon, and the same area of silicon could make more than two of the 9.3 million-transistor K6-2 CPUs. For a time, the K6-III was a low priority part for AMD—something to be made only when all orders for high-priced Athlons and cheap-to-produce K6-2s had been filled—and it became difficult to obtain in significant quantities.
The original K6-III went out of production when Intel released their "Coppermine" Pentium III (a much improved part that used internal, on-die cache like a Celeron or a K6-III) and, at the same time, switched to a new production process. The changeover was fraught with difficulties and Intel CPUs were in global short supply for 12 months or more. This, coupled with the outstanding performance of the Athlon, resulted in even many former Intel-only manufacturers ordering Athlon parts, and stretched AMD's manufacturing facilities to the limit. In consequence, AMD stopped making the K6-III in order to leave more room to manufacture Athlons (and K6-2s).
By the time the global CPU shortage was over, AMD had developed revised versions of the K6 family: the K6-2+ and the K6-III+. Essentially, both parts were K6-IIIs (the 2+ with a 128 KiB cache, the III+ with the full 256 KiB) made on a new 180nm production process. They were also the first processors to be available with the PowerNow! power saving technology. Essentially, the power savings were achieved with a combination of frequency (through adjusting multipliers) and voltage reduction.
Although targeted at notebook computers, both parts were also used by enthusiasts in desktop systems. AMD continued to devote their marketing resources to the Athlon and neither part became well-known outside the industry, but both had modest success and became firm favourites with the overclocking community. K6-III+ 450 MHz CPUs routinely overclocked to almost 600 MHz. Unfortunately, even with the 180 nm process, the K6 architecture's short 6-stage pipeline was stretched to the limit with regards to clock speed ramping. While the new "Coppermine" Pentium III was able to rise up to a final 1.13 GHz clock speed, K6 III+ and 2+ never clocked higher than 570 MHz officially, with overclockers using air cooling achieving around 600 MHz at best.
Models
K6-III ("Sharptooth", K6-3D+, 250 nm)
- CPU ID: AuthenticAMD Family 5 Model 9
- L1-Cache: 32 + 32 KiB (Data + Instructions)
- L2-Cache: 256 KiB, fullspeed
- MMX, 3DNow!
- Socket 7, Super7
- Front side bus: 66/100, 100 MHz
- VCore: 2.2 V, 2.4 V
- First release: February 22, 1999
- Manufacturing process: 0.25 µm
- Clockrate: 400, 450 MHz
K6-III-P (250 nm, mobile)
- CPU ID: AuthenticAMD Family 5 Model 9
- L1-Cache: 32 + 32 KiB (Data + Instructions)
- L2-Cache: 256 KiB, fullspeed
- MMX, 3DNow!
- Socket 7, Super7
- Front side bus: 66, 95, 96.2, 66/100, 100 MHz
- VCore: 2.0 V, 2.2 V
- First release: May 31, 1999
- Manufacturing process: 0.25 µm
- Clockrate: 350, 366, 380, 400, 433, 450 MHz
K6-III+ (180 nm, mobile)
- CPU ID: AuthenticAMD Family 5 Model 13
- L1-Cache: 32 + 32 KiB (Data + Instructions)
- L2-Cache: 256 KiB, fullspeed
- MMX, Extended 3DNow!, PowerNow!
- Super7
- Front side bus: 95, 100 MHz
- VCore: 2.0 V, (1.6 V, 1.8 V low voltage types)
- First release: April 18, 2000
- Manufacturing process: 0.18 µm
- Clockrate: 400, 450, 475, 500 MHz. (550 MHz, undocumented)
External links
- AMD
- AMD
- AMD
- at sandpile.org
- at Tom's Hardware
- at AcesHardware.Com
- at AcesHardware.Com
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