AMD K6, K6-2, K6-III, K6-III+
The first K6 were intended as a direct competition for Pentium MMX and later Pentium II. Looking at the results, it is clear the K6 is a good match for the Pentium MMX, even in applications few years younger than the processors in question. K6 is somewhat faster in multimedia encoding, photo editing and file compression. Pentium on the other hand has the lead in games and rendering.
On the other hand K6 is rather weak when compared to the P6 architecture. On average 200 MHz Pentium Pro is 30% faster than K6 233 and Pentium II 233 enjoys massive 70% lead. While K6-2 brings some improvement, it is merely 10% over the original K6 clock to clock. This is not enough to compete with Mendocino Celerons. 450 MHz K6-2 is 33% slower than Celeron 433.
According to some contemporary reviews K6-III was supposed to be equal to Pentium III or even beat it in some applications. This is not the case here, not by far. The fast on-die L2 cache adds about 20% more performance when compared to the K6-2. But even then 450 MHz K6-III can only match Celeron 333 and ends up 37% behind PIII 500.
The whole K6 line fell behind rather quickly and couldn't keep up with Pentium II/III and Celeron. Athlon on the other hand did very well back in 1999 and can compete with Pentium III even now. Just like P6, K7 also was long-lived architecture and lasted many years. Therefore most applications were optimized for both K7 and P6. Athlon is very strong in synthetic benchmarks, rendering and games. Athlon started long lasting domination of AMD in gaming segment - it lasted for the rest of PIII generation and for the whole NetBurst era.
There aren't many weak spots on the first generation of K7. But they are rather significant. The worst problem is high power consumption. By today's standards 40 - 50 W Athlon could be described as power-efficient. But at the time 50 W was a lot, especially for classic (non-heatpipe) aluminum heatsink with pair of 50mm fans. Even bigger issue is lack of good chipsets (just like in case of Socket 7). There are just two for the Slot A platform - AMD-750 and VIA KX133. The first one was launched along with the first Athlons and for some time there was no other choice. AMD-750 is limited to AGP 2x and PC100 SDRAM. This limits the performance to some extent. VIA KX133 address these issues but at the cost of not so good AGP compatibility and problematic southbridge VT82C686A.
Intel Pentium, Pentium MMX
Surprisingly, the difference between Pentium Classic and Pentium MMX is rather small. Despite the fact tested applications are several years younger than Pentium MMX, it seems they can't take advantage of MMX inctruction set. The only exception is Ulead Video Studio which simply doesn't run without MMX at all. Even then the performance difference in only 20%, for which to some extent the doubled L1 cache is responsible. The most significant advantage of Pentium MMX is no doubt the more advanced manufacturing process. Every MMX can reach at least 250 MHz overclock and the better pieces even 300 MHz.
Intel Pentium Pro, Pentium II, Pentium III
The P6 architecture turned out to be very future-proof, even in its forst implementation, the Pentium Pro (1995). In relatively modern applications beat much younger competitors. Synthetic benchmarks and cache / RAM benchmarks aren't the strong suite of Pentium Pro. On the other hand in rendering and games it really shines. The best suited load for Pentium Pro seems to be compression and file operation - here overclocked 233 MHz Pentium Pro almost matches K6-III 450.
Pentium II despite the slower L2 cache (1/2 of core speed) is faster in most of the applications. Most definitely some part of the performance uplift is due to the much stronger i440BX chipset and also SDRAM memory. Later Pentium II 450 and Pentium III 500 most of the time has no problem to beat any K6 processors. PIII Coppermine raises the bar even higher, with higher frequency, fast on-die cache, 133 MHz bus speed and RDRAM memory, it dominates file compression and photo edit categories. Surprisingly it is not that great in games. Perhaps this is caused by conservative BIOS settings of the Intel VC820 motherboard.
Cyrix 6x86, MII, IDT Winchip C6
Cyrix 6x86L PR166+ is by far the worst processor of the whole test. Updated Cyrix MII (or 6x86MX) perform somewhat better, but this is most likely due to increased frequency and not architectural improvements. The resulst clearly indicate the Pentium Rating is exaggerated. MII PR233 runst at 187.5 MHz (2.5x75), yet it ends up equally fast as Pentium 166 MMX and K6 166.