The Big Processor Guide - Families
While "microarchitectures" would be a more technically correct term, the function of this page is to enumerate the major groups of processors that have come to market.
A "family" of only one core, and that core owing much to the 486, Am5x86 was sold by AMD to bolster their sales as the K5 design process drug on. While history has largely forgotten these chips, they were in their time a solid and generally compatible upgrade for 486 owners, escaping the 2x multiplier limit of 486 boards by simply interpreting that 2x multiplier setting as a 4x multiplier. Only one chip in this "family" was ever mass-produced; it rates a mention here largely because it was the very first chip to be marked with a P-rating.
Trivia: While it is listed here as a Socket 3 part, the Am5x86 was compatible with Socket 1, 2, and even 486 with the addition of a voltage regulator. Some third parties sold packages that included the voltage regulator and a socket converter. The chip continues to this day to enjoy popularity in embedded products, and AMD continues to manufacture a version targeted at the embedded market.
The K5 was AMD's first major attempt at a 486 successor. And it was a flop. Delivered late to market, without a clear performance or price advantage, the market turned its nose up at it. The K5 was a very ambitious design, and on paper it was radically superior to the Pentium on a technological basis. But flaws in the implementation and AMD's unremarkable manufacturing facilities caused the K5 to lag behind.
There were two K5 cores, and the second generation improved performance quite a bit—in AMD's reckoning, pushing it ahead of the Pentium. However, the improved performance was not enough to regain much marketshare.
Trivia: The "K" is purported to stand for Kryptonite. That is, something capable of stopping the otherwise unstoppable.
Based (very heavily) on the Nx686 design by NexGen, a company AMD had recently acquired, the K6 was technologically a complete and total break from the K5. Launched a month before the Pentium II, and performing similarly for less money, the K6 family may well have saved AMD from being shoved out of the processor market.
The K6 family includes the original K6, K6-2, K6-III, and "plus" versions for laptops.
Trivia: K6 family core names include "Little Foot", "Chompers", and "Sharptooth", all of which are purportedly references to the children's movie series, The Land Before Time. The NexGen design that was the basis of the K6 was co-developed by Vinod Dahm, who invented the Pentium processor.
A substantially reworked K6, the K7 family was a very lucky group. Launched originally (in the form of the Athlon) to compete with the Pentium III, K7s would continue to hit the market through much of the Pentium 4's very long lifespan. Manufacturing difficulties with the Pentium III gave AMD an excellent opportunity to expand their market. Later K7s would demonstrate substantially better performance per clock than Pentium 4 competitors, leading AMD to revive the "P Rating" system. While the first few generations of K7 processors suffered much more severe heat concerns than their competition, by the end of their cycle the situation had reversed, and it was Intel struggling to keep cool its Pentium 4 Prescott. K7 chips initially had off-die L2 cache (they used a slot configuration), but later designs moved the cache on-die. All K7s have quite large amounts of L1 cache.
The K7 family includes the Athlon, Athlon XP, Duron, and some Semprons.
Trivia: Several K7 cores are named for horses, including the entire Athlon XP series.
AKA Hammer. In the eyes of many, K8 is the golden goose. K8 marked a major technological coup for AMD as they greatly leapfrogged Intel. The K8 microarchitecture added the 64-bit AMD64 instruction set, which Intel was soon pressured into implementing. But more to the point, K8 chips performed very, very well. A major part of that performance is the integrated memory controller: all K8 chips have the memory controller integrated into the CPU itself, and not on the Northbridge. K8s also have relatively large L2 caches for AMD: initially all had 1 MB, but subsequently processors have been available with both 512 KB and 1 MB. K8 brought a lot of firsts: first x86 chips with an integrated memory controller, first 64-bit desktop processor, and first use of Silicon On Insulator technology in a processor.
The K8 family includes the Athlon 64, Athlon 64 FX, Athlon 64 X2, Opteron, and many Semprons.
Trivia: The first grouping of K8 parts were named for types of hammers to reinforce that this was the Hammer architecture. Reportedly, the name Hammer was chosen to imply the ability to crush the competition. In later generations the Opterons were named after countries (mostly), while other series were named after cities.
A revision of K8, K8L brings a variety of mostly-small changes. The L is generally taken to be for Low power. The introduction of K8L will coincide with a die shrink to 65 nm, and is expected to facilitate a jump to quad core chips; K8L is supposedly a native-quad-core design.
K10 is believed to be the name for AMD's future microarchitecture. K9 was skipped, supposedly to avoid confusing people about the Athlon 64 X2. My personal theory is that they didn't want to deal with a lot of K-9 (canine) jokes. There are all sorts of rumors about whether K10 will actually come to market, and it is often claimed that the original project bearing the name has in fact been cancelled, and it was reassigned. This is all speculation.
Intel's 586, the P5 had a number of advantages over the 486. Chief among these was its superscalar nature: it had multiple pipelines to execute multiple instructions per clock cycle.
The P5 family includes the Pentium and Pentium MMX.
Trivia: The name "Pentium" derives largely from the prefix pent-, which indicates 5. The Pentium was essentially a 586.
The Phoenix of microarchitectures, the P6 is an impressively durable design. It is noted mainly for excellent energy efficiency. Originating with the Pentium Pro, it was adapted for use in the Pentium II, then the Pentium III, and then shelved for a time in favor of NetBurst. However, it was revived for the Pentium M, and then became a part of the new Core microarchitecture.
The P6 family includes the Pentium Pro, Pentium II, Pentium III, Pentium M, and Core Solo/Duo chips. It also includes some Celerons and Xeons (all Xeons not noted as Xeon DP or Xeon MP on these pages are P6-based).
Arguably, the bet that didn't pay off. NetBurst's primary distinguishing factor is a very long pipeline: at introduction 20 stages, peaking out at 31. This compared to the Pentium III (P6 family) and its 10 stages. This lengthy pipeline makes NetBurst cores excellent at tasks such as encoding, but becomes a hindrance in tasks where branch prediction errors are more frequent.
The NetBurst family includes the Pentium 4, Pentium D, Celeron D, and many Celerons and Xeons.
Trivia: Most of the NetBurst family is named after rivers and towns in the Pacific Northwest.
Taking the best of P6 and NetBurst, or perhaps splitting the difference between them, Core is aimed at pushing back AMD's advances. While principally quite similar to P6, Core centers on a somewhat different design philosophy: designed for low power and also multiple cores. Core features more advanced power management, linked L1 and shared L2 caches, and macro-ops fusion. It achieves much better performance at lower clock speeds than Netburst, while also demanding much less power.
The Core family includes the Xeon Woodcrest and the Core 2 line.
Future? Nehalem was originally a code name for some breed of Pentium 5. But then that core (which would have followed also-cancelled Tejas) was scrapped. More recently, the name has been used to refer to a future microarchitecture utilizing the Common System Interface. Or maybe a Xeon of some description. Is there anything to it? Maybe, maybe not. Stay tuned.