The QuantiSpeed architecture is one of AMD used name of the microarchitecture of its processors on K7 basis. Originally the architecture was known under the name "K7 architecture", but this was revised with the introduction of the Athlon XP, so that AMD - also for marketing reasons - introduced a new name.
Just like the Intel Core microarchitecture meanwhile , AMD uses Quantispeed, a more efficient architecture with which, however, only moderate clock rates can be achieved.
The architecture has the following characteristics:
- A nine-tier, superpipelined and superscalar x86 microarchitecture that has been optimized for increased IPC .
- A fully-pipelined FPU that also executes all MMX , SSE and 3DNow commands.
- A data "prefetch" unit, which optimizes and accelerates the execution of applications
- A two-stage translation lookaside buffer (TLB)
CPUs with QuantiSpeed architecture
- AMD Geode NX
- AMD Athlon XP
- AMD Athlon XP-M
- AMD Athlon MP
- AMD Duron (from Morgan)
- AMD Mobile Duron (from Morgan)
- AMD Sempron (K7)
However, Duron and Mobile Duron do not have a QuantiSpeed rating.
Along with the new name for the microarchitecture, AMD also introduced a rating system for its QuantiSpeed processors. The background to this measure is the fact that Intel had optimized the NetBurst architecture of the Pentium 4 (and its offshoots Celeron , Mobile Pentium 4 and Xeon ) to the highest possible clock rate, but at the expense of the computing power per clock. AMD processors, on the other hand, use a low clock rate, but execute more instructions. Corresponding processors are effectively equally fast for many tasks. The higher clock frequency of the Pentium 4, however, meant an advantage for Intel processors in marketing, as the technically inexperienced customers were often led to believe that it had a higher performance. AMD responded with the QuantiSpeed rating for Athlon XP and Sempron, which ensures direct comparability with the Pentium 4 processors. The "+" in the name should even turn the tables and make it clear that the processor is actually even faster than the associated rating, i.e. faster than the respective competing product.
AMD as well as Cyrix and Centaur already used a system called P-Rating in the 1990s to put the performance of their CPUs in relation to the respective Intel CPUs. However, the CPUs of that time were mostly far superior to their Intel counterparts in terms of integer performance, while the FPU performance was drastically worse. Depending on the application, the P-Rating was set either too high or too low, which brought a negative aspect to the whole system. As the FPU performance became more and more important, the imbalance of the P ratings continued to worsen. AMD got rid of it with the AMD K6 , although these CPUs also had advantages over the respective Intel CPUs in terms of integer performance.
Definition of the numbers for the Athlon XP
According to AMD, the QuantiSpeed rating is not related to Intel products, but is intended to describe the performance compared to an Athlon Thunderbird. An Athlon XP-3200 + would have the same performance as an Athlon Thunderbird with 3200 MHz. In reality, however, the QuantiSpeed rating is set in relation to Intel's clock rate for the Pentium 4 processors, which is certainly also desired by AMD. Since AMD reached its limits with the timing of the Athlon XPs, the QuantiSpeed rating was stretched more and more upwards. While an Athlon XP-1500 + with 1333 MHz was almost exactly the same as or faster than an Athlon Thunderbird with 1500 MHz or a Pentium 4 1500, an Athlon XP-3200 + with 2200 MHz was by far not as fast as a Pentium 4 3200, and also a hypothetical Athlon Thunderbird 3200 would have been much faster. This effect was ultimately caused by AMD's decision to include both the size of the L2 cache and the front side bus in the rating. Both factors have an influence on the performance of the CPU, but do not have a general effect, but are limited to certain types of application. There are many Athlon XPs with widely different quantispeed ratings, but with roughly the same clock frequency, which only differ in the L2 cache and FSB.
Definition of the numbers for the Athlon 64
Since the framework conditions did not change significantly when the Athlon 64 was launched, AMD also used a rating system for these CPUs that takes into account the clock frequency, size of the L2 cache and the number of memory channels. AMD no longer officially calls these numbers Quantispeed Rating, but only model numbers, but the methodology and the intention behind them have remained the same.
Determination of the numbers at Sempron
Since the AMD Duron the same problem as previously occurred when Athlon - the clock frequency between AMD Duron and Intel Celeron gaped far apart, although both CPUs in effect comparable performance had - led AMD to pressure large manufacturer a new CPU family named AMD Sempron one and named the processors also after the QuantiSpeed rating. In reality, this rating is based on the direct Sempron competitor Celeron, and not on the faster Pentium 4.