Hardware Secrets
Home | Camera | Case | CE | Cooling | CPU | Input | Memory | Mobile | Motherboard | Networking | Power | Storage | Video | Other
Content
Articles
First Look
Gabriel's Blog
News
Reviews
Tutorials
Main Menu
About Us
Awarded Products
Compare Prices
Datasheets
Dictionary
Download
Drivers
Forums
Links
Manufacturer Finder
Newsletter
On The Web
RSS Feed
Test Your Skills
Twitter
Newsletter
Subscribe today!
Search




Recommended
The Winn L. Rosch Hardware Bible, 6th Edition (2 Vol. Set)
The Winn L. Rosch Hardware Bible, 6th Edition (2 Vol. Set), by Winn L Rosch (Que), starting at $2.31
Home » CPU
Inside Intel Core Microarchitecture
Author: Gabriel Torres
Type: Tutorials Last Updated: April 12, 2006
Page: 6 of 7
$ Check REAL-TIME pricing for Intel Core i7-860 Lynnfield 2.8GHz 8MB L3 Cache LGA 1156 95W Quad-Core Processor - Retail BX80605I7860 i7 $.
Newegg: $289.99 CircuitCity: $279.99
TigerDirect: $279.99 Directron: $297.99

Memory Disambiguation

Memory disambiguation is a technique to accelerate the execution of memory-related instructions.

All Intel CPUs since Pentium Pro have an out-of-order engine, which allows the CPU to execute non-dependant instructions in any order. What happens is that memory-related instructions are traditionally executed in the same order they appear on the program, otherwise data inconsistency could appear. For example, if the original program has an instruction like “store 10 at address 5555” and then a “load data stored at 5555”, they cannot be reversed (i.e. executed out of order) or the second instruction would get wrong data, as the data of address 5555 was changed by the first instruction.

What the memory disambiguation engine does is locate and execute memory-related instructions that can be executed out of order, accelerating the execution of the program (we will explain how this is accomplished in a minute).

On Figure 3 you have an example of a CPU without memory disambiguation (i.e. all CPUs not based on Core microarchitecture). As you can see, the CPU has to execute the instructions as they appear on the original program. For example, “Load4” isn’t related to any other memory-related instruction and could be executed first, however it has to wait all other instructions to be executed first.

Core Microarchitecture
click to enlarge
Figure 3: CPU without memory disambiguation.

On Figure 4 you see how the program shown on Figure 3 works on a CPU based on Core microarchitecture. It “knows” that “Load4” isn’t related to the other instructions and can be executed first.

Core Microarchitecture
click to enlarge
Figure 4: CPU with memory disambiguation.

This improves the CPU performance because now that “Load4” is executed, the CPU has the data required for executing other instructions that need the value of “X” to be executed.

On a regular CPU, if after this “Load4” we had an “Add 50”, this “Add 50” (and all other instructions that depend on that result) would have to wait all other instructions shown on Figure 3 to be executed. With memory disambiguation, these instructions can be executed early, since the CPU will now have the value of “X” early.

Pages (7): « 1 2 3 4 5 [6] 7 »
Print Version | Send to Friend | | Bookmark Article | Comments (0)

Related Content
  • IDF Fall 2005 Coverage
  • IDF Tel Aviv 2005 Coverage
  • Core 2 Duo E6700 and Core 2 Extreme X6800 Review
  • All Core 2 Models
  • Everything You Need to Know About The Centrino Platform

  • Recommended Deal.
    Power Supply VX450W 450W ATXCorsair CMPSU-450VX VX450W ATX12V & EPS12V Power Supply 450w VX Series 12v ATX 80 Plus Certified C3PLRL


    Buy.com: $74.42 Wal-Mart: $89.98
    Newegg: $64.99 TigerDirect: $79.99

    RSSLatest News
    IN WIN LAN Party in Southern California
    November 20, 2009 - 12:37 PM PST
    Patriot Announces PS-100 SSD Series
    November 19, 2009 - 7:30 AM PST
    Antec Launches TPQ-1200 PSU
    November 18, 2009 - 11:30 AM PST
    AMD/ATI Launches Radeon HD 5970
    November 18, 2009 - 10:18 AM PST
    OCZ Launches Colossus SSD Series
    November 17, 2009 - 1:39 PM PST
    NZXT Unleashes Tempest EVO Mid-Tower Case
    November 17, 2009 - 1:06 PM PST
    nVidia Launches GeForce GT 240
    November 17, 2009 - 10:18 AM PST
    Arctic Cooling Announces Accelero TWIN TURBO PRO VGA Cooler
    November 16, 2009 - 11:46 AM PST
    PowerColor Announces PLAY! HD5770 Video Card
    November 13, 2009 - 12:51 PM PST
    G.Skill Announces Falcon II SSD Series
    November 11, 2009 - 3:31 PM PST
    .:: More News ::.

    RSSLatest Content
    Ultra X4 500 W Power Supply Review
    Seagate Barracuda XT 2 TB Hard Disk Drive Review
    Nintendo Wii Fit Plus Review
    AMD ATI Chips Comparison Table
    nVidia Chips Comparison Table
    Gigabyte G41M-ES2L Motherboard
    Netflix on Playstation 3 Review
    CM Storm Sentinel Advance Mouse Review
    Titan Skalli CPU Cooler Review
    Nexus RX-6300 630 W Power Supply Review
    Gigabyte P55-UD6 Motherboard
    Nintendo Wii Review
    SilverStone Grandia GD04 Case Review
    Can We Trust the 80 Plus Certification?
    NZXT Gamma Case Review

    Our Most Popular Articles
    Maximum CPU Temperature
    1,078,668 views
    How to Find Out Your Motherboard Manufacturer and Model
    706,689 views
    nVidia Chips Comparison Table
    679,448 views
    Connecting Two PCs Using a USB-USB Cable
    593,764 views
    How To Correctly Apply Thermal Grease
    562,766 views
    AMD ATI Chips Comparison Table
    560,358 views
    ATI Radeon X1300 Pro Review
    488,021 views
    ATI Radeon X1600 XT Review
    477,178 views
    How To Perform a BIOS Upgrade
    394,733 views
    Sempron vs. Athlon XP
    338,600 views

    Latest Threads in Our Forums
    Dell Inspiron 6000 Powers but will not boot...
    by Merman
    Ultra X4 500 W Power Supply Review
    by Merman
    IN WIN LAN Party in Southern California
    by Hardware Secrets Team
    Getting A Hard Copy
    by Trevorrross
    Am I Making The Right Choice?
    by need2know
    Is it available to mount the Zalman cooler?
    by Olle P
    dsl modem prob
    by Sherry
    Seagate Barracuda XT 2 TB Hard Disk Drive Review
    by Hardware Secrets Team
    Overclocking a dell xps 410
    by 6dracing
    How to recover mp3's, pdf & chm files, applications from formated harddrive partition
    by tomahawk 1705
    .:: Visit Our Forums ::.


    © 2004-9, Hardware Secrets, LLC. All rights reserved.
    Advertising | Legal Information | Privacy Policy
    All times are Pacific Standard Time (PST, GMT -08:00)