The Processor Performance Rating (P-rating) specification defines a methodology created by several companies including: AMD, Cyrix, IBM Microelectronics, and SGS-Thomson. The specification is designed to provide a credible, consistent, and easy-to-understand method for rating processor performance. Earlier methods of rating processors relied on a combination of architecture (e.g., 5-class, 6-class) and clock speed - a system that was confusing and failed to provide a good measure of real application performance. This system provides a single rating number for a processor (the P-rating) that gives a true measure of application performance and allows an "apples-to-apples" comparison among different processors on the market.
The goals of the processor performance rating specification are:
This methodology is judged to be a credible and accurate method as determined by all parties as of January 25, 1996. As newer benchmark tools become available and as the industry evolves to adopt newer OS and application programs this specification will need to be modified accordingly.
The process for obtaining a performance rating for a processor is as follows:
The following table lists the hardware components that must be disclosed in the final results as well as examples for each component. All configuration parameters in the vendor and reference platforms must be disclosed in the test results.
COMPONENT EXAMPLE Motherboard Asus P/I - P55SP4 rev 1.4 Chipset SiS 5511 Disk drive and drive controller Quantum Fireball 1280A drive, ATA-2 PCI controller Video card, video resolution, software driver Diamond Stealth 64 3200XL PCI graphics card with 2 Mbytes of VRAM. First production release of Diamond Stealth driver. 1024 x 768 resolution, 256 colors at 75 Hz. Main memory type and speed 16 Mbytes of EDO DRAM (60ns) L2 cache type and speed 256-Kbyte synchronous pipeline burst SRAM 3,1,1,1 (8 ns) PCI bus speed 33 Mhz(Speed of PCI bus must match clock rates defined in PCI 2.1 specification)
The hardware components listed in the table above are examples only. Individual vendors may choose to substitute other components as required. This allows the rating system to accommodate architectural, design, and positioning requirements for the processor being rated, ensuring a credible "apples-to-apples" comparison.
Note that both the vendor system and the reference system must have identical components. If identical systems cannot be provided due to architectural differences (i.e., processors with different bus interface protocols), like components can be substituted. Any substitutions should be fully documented.
When running the benchmark tests on both the vendor and reference platforms, use the operating system and software configuration parameters listed in the table below:
COMPONENT CONFIGURATION Operating System Windows 95 first production release File System 32-bit with 4 Mbytes of cache Virtual Memory 32-bit Disk Compression Not installed Virtual Memory Maximum 32 Mbytes, minimum 32 Mbytes Read-Ahead Optimization Full
This particular configuration was chosen in order to minimize deviations of the benchmark testing. No performance advantage or disadvantage has been observed by using this configuration relative to the Windows 95 default settings.
Testing is based on Ziff-Davis's Winstone 96 benchmark. The process used to obtain a benchmark number is as follows:
1. Use the reference platform equipped with various Pentium microprocessors (e.g., Pentium-75, Pentium-90, Pentium-100, etc.) to obtain an index table using the methodology described in section 5.
Pentium Frequency 75 MHz 90 MHz 100 MHz 120 MHz 133 MHz Winstone 96 score 46.1 52.9 55.8 59.3 63.4
Adjust the values in the index table down by 1.5% to compensate for the natural variation in the Winstone 96 test (no greater than 3% total variation as specified by Ziff-Davis Benchmark Operation). This results in the following table:
Pentium Frequency 75 MHz 90 MHz 100 MHz 120 MHz 133 MHz Winstone 96 score 45.4 52.1 55.0 58.4 62.4
2. Using the vendor platform, run the benchmark with the processor you want to rate. Note that the vendor platform and the reference platform must have the same hardware configuration.
The vendor then runs the benchmark on their processor and obtains a score of 57.1.
3. The P-rating number as currently defined is chosen to conform to a standard Pentium microprocessor frequency. To obtain the P-rating, compare the vendor processor benchmark score to the table of adjusted values obtained in step 1. The P-rating for the vendor processor is assigned according to a score that is greater than or equal to the scores listed in the adjusted table.
Since 57.1 is greater than 55.0 but less than 58.4, the processor has a P-rating of P100.
Once the P-rating is defined, it can be used to describe the processor's performance in collateral material, on the processor chip, and when providing rating information to the press.
When a vendor reports P-rating results in published literature like collateral, press releases, and web sites, the literature must disclose all configuration parameters used to generate the P-rating. Configuration parameters are the rows in the tables in section 3. Additionally, any deviations from this specification must be clearly documented.
Reporting P-rating results in this manner will allow OEMs, the press, and consumers to reproduce and validate the P-rating for the processor. This ensures credibility for both the vendor's P-rating numbers and for the overall P-rating system.
Issued jointly by Advanced Micro Devices, Cyrix Corporation, IBM Microelectronics Division, SGS-Thomson