Hardware Reference
In-Depth Information
terface to create a drop-in Pentium-compatible chip called the K6, which actually outper-
formed the original from Intel.
The Nx586 had all the standard fifth-generation processor features, such as superscalar
execution with two internal pipelines and a high-performance integral L1 cache with sep-
arate code and data caches. One advantage is that the Nx586 includes separate 16KB in-
struction and 16KB data caches, compared to 8KB each for the Pentium. These caches
keep key instructions and data close to the processing engines to increase overall system
performance.
TheNx586alsoincludes branchprediction capabilities, whichareoneofthehallmarks of
asixth-generationprocessor.Branchpredictionmeanstheprocessorhasinternalfunctions
to predict program flow to optimize the instruction execution.
The Nx586 processor also featured a RISC core. A translation unit dynamically translates
x86 instructions into RISC86 instructions. These RISC86 instructions were designed spe-
cifically with direct support for the x86 architecture while obeying RISC performance
principles. They are simpler and easier to execute than the complex x86 instructions. This
type of capability is another feature normally found only in P6 class processors.
The Nx586 was discontinued after the merger with AMD, which then took the design for
the successor Nx686 and released it as the AMD-K6.
AMD-K6 Series
The AMD-K6 processor is a high-performance sixth-generation processor that is physic-
ally installable in a P5 (Pentium) motherboard. It essentially was designed for AMD by
NexGen and was first known as the Nx686. The NexGen version never appeared because
AMD purchased it before the chip was due to be released. The AMD-K6 delivers per-
formance levels somewhere between the Pentium and Pentium II processor because of its
unique hybrid design.
The K6 processor contains an industry-standard, high-performance implementation of the
new multimedia instruction set, enabling a high level of multimedia performance for the
period. The K6-2 introduced an upgrade to MMX that AMD calls 3DNow!, which adds
even more graphics and sound instructions. AMD designed the K6 processor to fit the
low-cost, high-volume Socket 7infrastructure. Initially,itusedAMD's0.35-micron,five-
metal layer process technology; later the 0.25-micron process was used to increase pro-
duction quantities because of reduced die size, as well as to decrease power consumption.
AMD-K6 processor technical features include the following:
• Sixth-generation internal design, fifth-generation external interface
• Internal RISC core, which translates x86 to RISC instructions
