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Processor Benchmarks And Comparing Performance

Upgrading And Repairing PCs 21st Edition: Processor Specifications
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Processor Benchmarks

People love to know how fast (or slow) their computers are. We have always been interested in speed; it is human nature. To help us with this quest, we can use various benchmark test programs to measure aspects of processor and system performance. Although no single numerical measurement can completely describe the performance of a complex device such as a processor or a complete PC, benchmarks can be useful tools for comparing different components and systems.

However, the only truly accurate way to measure your system’s performance is to test the system using the actual software applications you use. Although you think you might be testing one component of a system, often other parts of the system can have an effect. It is inaccurate to compare systems with different processors, for example, if they also have different amounts or types of memory, different hard disks, different video cards, and so on. All these things and more skew the test results.

Benchmarks can typically be divided into two types: component or system tests. Component benchmarks measure the performance of specific parts of a computer system, such as a processor, hard disk, video card, or optical drive, whereas system benchmarks typically measure the performance of the entire computer system running a given application or test suite. These are also often called synthetic benchmarks because they don’t measure actual work.

Benchmarks are, at most, only one kind of information you can use during the upgrading or purchasing process. You are best served by testing the system using your own set of software OSs and applications and in the configuration you will be running.

I normally recommend using application-based benchmarks such as the BAPCo SYSmark to measure the relative performance difference between different processors or systems.

Comparing Processor Performance

A common misunderstanding about processors is their different speed ratings. This section covers processor speed in general and then provides more specific information about Intel, AMD, and VIA/Cyrix processors.

A computer system’s clock speed is measured as a frequency, usually expressed as a number of cycles per second. A crystal oscillator controls clock speeds using a sliver of quartz sometimes housed in what looks like a small tin container. Newer systems include the oscillator circuitry in the motherboard chipset, so it might not be a visible separate component on newer boards. As voltage is applied to the quartz, it begins to vibrate (oscillate) at a harmonic rate dictated by the shape and size of the crystal (sliver). The oscillations emanate from the crystal in the form of a current that alternates at the harmonic rate of the crystal. This alternating current is the clock signal that forms the time base on which the computer operates. A typical computer system runs millions or billions of these cycles per second, so speed is measured in megahertz or gigahertz. (One hertz is equal to one cycle per second.) An alternating current signal is like a sine wave, with the time between the peaks of each wave defining the frequency (see the figure below).

Note: The hertz was named for the German physicist Heinrich Rudolf Hertz. In 1885, Hertz confirmed the electromagnetic theory, which states that light is a form of electromagnetic radiation and is propagated as waves.

A single cycle is the smallest element of time for the processor. Every action requires at least one cycle and usually multiple cycles. To transfer data to and from memory, for example, a processor such as the Pentium 4 needs a minimum of three cycles to set up the first memory transfer and then only a single cycle per transfer for the next three to six consecutive transfers. The extra cycles on the first transfer typically are called wait states. A wait state is a clock tick in which nothing happens. This ensures that the processor isn’t getting ahead of the rest of the computer.

Alternating current signal showing clock cycle timing.Alternating current signal showing clock cycle timing.

The time required to execute instructions also varies:

  • 8086 and 8088—The original 8086 and 8088 processors take an average of 12 cycles to execute a single instruction.
  • 286 and 386—The 286 and 386 processors improve this rate to about 4.5 cycles per instruction.
  • 486—The 486 and most other fourth-generation Intel-compatible processors, such as the AMD 5x86, drop the rate further, to about 2 cycles per instruction.
  • Pentium/K6—The Pentium architecture and other fifth-generation Intel-compatible processors, such as those from AMD and VIA/Cyrix, include twin instruction pipelines and other improvements that provide for operation at one or two instructions per cycle.
  • P6/P7 and newer—Sixth-, seventh-, and newer-generation processors can execute as many as three or more instructions per cycle, with multiples of that possible on multicore processors.

Different instruction execution times (in cycles) make comparing systems based purely on clock speed or number of cycles per second difficult. How can two processors that run at the same clock rate perform differently, with one running “faster” than the other? The answer is simple: efficiency.

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Top Comments
  • 11 Hide
    DelightfulDucklings , October 14, 2013 10:22 PM
    Very interesting article, I quite enjoyed the part about Cache memory
Other Comments
  • 5 Hide
    xkm1948 , October 14, 2013 9:13 PM
    Really nice intro article!
  • 11 Hide
    DelightfulDucklings , October 14, 2013 10:22 PM
    Very interesting article, I quite enjoyed the part about Cache memory
  • 2 Hide
    kindiana , October 14, 2013 10:27 PM
    nice article
  • 9 Hide
    burnley14 , October 14, 2013 10:29 PM
    One of the most interesting and informative articles I've ever read on the site. Great job!
  • 2 Hide
    aredflyingbird , October 14, 2013 10:41 PM
    Agreed, excellent article.
  • 2 Hide
    palladin9479 , October 14, 2013 10:55 PM
    Really good article, actually was spot on with how caching works.
  • 3 Hide
    AndrewJacksonZA , October 15, 2013 12:22 AM
    "Forward From The Editor"
    Shouldn't that be "Foreword?"
  • 3 Hide
    iam2thecrowe , October 15, 2013 2:23 AM
    I need more cache in my kitchen.
  • 0 Hide
    LalitMotagi , October 15, 2013 2:25 AM
    Great Article.
  • -1 Hide
    Rex Romero , October 15, 2013 2:30 AM
    Andrew. It's so advanced so it's forward. lol
  • 1 Hide
    groundrat , October 15, 2013 4:04 AM
    Excellent article.
  • 0 Hide
    ojas , October 15, 2013 5:22 AM
    Quote:
    For example, if you live on a street in which the address is limited to a two-digit (base 10) number, no more than 100 distinct addresses (00–99) can exist for that street (102). Add another digit, and the number of available addresses increases to 1,000 (000–999), or 103.

    Should be 10^2, 10^3, and in the next para, 2^x.
  • 0 Hide
    ojas , October 15, 2013 6:11 AM
    Quote:
    Note: Early versions of EM64T-equipped processors from Intel lacked support for the LAHF and SAHF instructions used in the AMD64 instruction set.

    This was very interesting, considering both instructions were supported even by the humble 8086.
  • 3 Hide
    spookyman , October 15, 2013 6:20 AM
    I have one still from 18 years ago. Still one of the best tech books I own. Though mine was just starting to touch the Intel Pentium processor. It even covered IBM's PS/2 computers and technology. Its amazing how much more hardware intensive PC's were back then they are now.
  • 0 Hide
    ojas , October 15, 2013 6:50 AM
    I ended up buying the 19th edition after last year's excerpts on Tom's Hardware, the 20th wasn't available in India then.

    These sections seem more or less unchanged, except for the mention of Ivy and Vishera, and i think the CPU-z screenshots are new as well.
  • 0 Hide
    AndrewJacksonZA , October 15, 2013 6:54 AM
    Quote:
    Quote:
    Note: Early versions of EM64T-equipped processors from Intel lacked support for the LAHF and SAHF instructions used in the AMD64 instruction set.

    This was very interesting, considering both instructions were supported even by the humble 8086.
    Apparently they were missing from the early 64bit CPUs from AMD and Intel. They appeared in March 2005 for AMD CPUs and June 2005 for Intel CPUs
    https://en.wikipedia.org/wiki/X86-64#Older_implementations

    Yet at the very least the 80386 supported them:
    http://css.csail.mit.edu/6.858/2011/readings/i386/LAHF.htm

    So it appears that it was an early-64 bit CPU issue only.
  • 0 Hide
    ta152h , October 15, 2013 9:04 AM
    I could only get to page three before being thoroughly disgusted by the lack of knowledge of the writer. How can he be writing books, without actually knowing the material?

    The Prescott introduced 64-bit to the Intel world, not the Core 2. Kind of common knowledge. The Athlon XP had a 36-bit address bus? I don't remember ever seeing that.

    Then we go to the misinformation about the 8086/8088 to 386.

    In actuality, there were four modes in the 80386. Real, Virtual 86, Protected 286, and Protected 386. Yup, four. And no, Windows 3.0 was not expected to run on an 8088 or 80286, because it DID use Virtual 86, which those processors could not support. You know, the part where they let you go from one DOS task to another. That was in the hardware. And that hardware started with the 80386.

    Moreover, the 80286 did NOT have the same instruction set as the 8086. Only in real mode did it. And why do you suppose it was called real mode? Maybe because the addresses were not virtualized? The 80286, as mentioned above, did have virtual addresses in what was called the 80286 Protected Mode. It not only ran Real Mode apps much faster, but when in Protected Mode was very capable of running multitasking Operating Systems, something that could not be done well on the 8086. It also increased the memory bus to 24-bits, albeit still using 64K bit segments.

    OS/2 1.x was the best example of an OS using 286 Protected mode, although any software using "Extended Memory" was taking advantage of the greater addressing of the 286, albeit in an inelegant way.

    I stopped reading after page three, as it's just discouraging to think people are writing books without being accurate. OK, so we have the author that got it wrong, fair enough, but what about the people who are supposed to error check it. I certainly don't know everything, and I know this stuff, and it's pretty basic. No one caught this? Are you kidding me? The 286 stuff might be a bit far away, but not knowing that x86-64 first appeared in the Prescott line is really difficult to understand, and is very basic. This is made more so because of all the rumors that the processor was made to support it, but Intel was hiding it so as to not undercut the Itanium. In time, it was proven true.

    Please, don't spread misinformation. Someone will repeat this stuff, and then someone else will, and it becomes 'fact' despite being wrong. If you publish a book, make a friggin effort! I'm sure I could errors the rest of the way, but it's just too annoying for me to wade through this rubbish.

    By the way, the term CPU bus is an ambiguous one. The CPU has multiple buses, and if you used that term with me, I'd wonder which one you were referring to. Find a more accurate term, like PCI-E bus if that's what you are trying to say.
  • -2 Hide
    ezorb , October 15, 2013 9:22 AM
    I feel that this is bellow the level of this website, even below the level of Maximum PC (which has a great podcast), this is the book my grandfather would buy if he wanted to try his hand at build a PC
  • -1 Hide
    hardrock40 , October 15, 2013 10:08 AM
    Really nice article well worth the read for sure.
  • -2 Hide
    ta152h , October 15, 2013 10:42 AM
    I could only get to page three before being thoroughly disgusted by the lack of knowledge of the writer. How can he be writing books, without actually knowing the material?

    The Prescott introduced 64-bit to the Intel world, not the Core 2. Kind of common knowledge. The Athlon XP had a 36-bit address bus? I don't remember ever seeing that.

    Then we go to the misinformation about the 8086/8088 to 386.

    In actuality, there were four modes in the 80386. Real, Virtual 86, Protected 286, and Protected 386. Yup, four. And no, Windows 3.0 was not expected to run on an 8088 or 80286, because it DID use Virtual 86, which those processors could not support. You know, the part where they let you go from one DOS task to another. That was in the hardware. And that hardware started with the 80386.

    Moreover, the 80286 did NOT have the same instruction set as the 8086. Only in real mode did it. And why do you suppose it was called real mode? Maybe because the addresses were not virtualized? The 80286, as mentioned above, did have virtual addresses in what was called the 80286 Protected Mode. It not only ran Real Mode apps much faster, but when in Protected Mode was very capable of running multitasking Operating Systems, something that could not be done well on the 8086. It also increased the memory bus to 24-bits, albeit still using 64K bit segments.

    OS/2 1.x was the best example of an OS using 286 Protected mode, although any software using "Extended Memory" was taking advantage of the greater addressing of the 286, albeit in an inelegant way.

    I stopped reading after page three, as it's just discouraging to think people are writing books without being accurate. OK, so we have the author that got it wrong, fair enough, but what about the people who are supposed to error check it. I certainly don't know everything, and I know this stuff, and it's pretty basic. No one caught this? Are you kidding me? The 286 stuff might be a bit far away, but not knowing that x86-64 first appeared in the Prescott line is really difficult to understand, and is very basic. This is made more so because of all the rumors that the processor was made to support it, but Intel was hiding it so as to not undercut the Itanium. In time, it was proven true.

    Please, don't spread misinformation. Someone will repeat this stuff, and then someone else will, and it becomes 'fact' despite being wrong. If you publish a book, make a friggin effort! I'm sure I could errors the rest of the way, but it's just too annoying for me to wade through this rubbish.

    By the way, the term CPU bus is an ambiguous one. The CPU has multiple buses, and if you used that term with me, I'd wonder which one you were referring to. Find a more accurate term, like PCI-E bus if that's what you are trying to say.
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