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What is tri channel memory?

What is tri channel memory?

The release of Intel’s new Nehalem-based Core i7 CPU has brought the demand for tri-channel memory to the desktop for the first time. In this short number, we’ll explore what it is, how it works, how to buy it, and how to avoid getting burned by Windows.

What is tri-channel memory?

Tri-channel memory overcomes the bandwidth limitations of individual memory modules by combining the bandwidth of three sticks at a time.

As the name might suggest, tri-channel memory requires that memory added to the system must be installed three (or in a rare case, four) sticks at a time. These sets of DDR3 modules must be installed in specific groups of memory slots, called channels, to enable dual or tri-channel functionality.

Activating tri-channel functionality requires that DRAM must populate DIMM#2 in channels A, B, and C, or all available DIMM slots.

At a minimum, DIMM#2 in channels A, B, and C must be populated to activate tri-channel bandwidth.

For other memory configurations, follow this simple table which outlines your options:

Installing different quantities of memory in different slots can change the channel configuration.

Installing different quantities of memory in different slots can change the channel configuration.

More broadly, any future chipset capable of supporting tri-channel memory must follow these rules:

  • All modules should be of the same speed.
  • All modules should be of the same capacity.
  • All modules should be of the same latency.
  • All memory configured in the system will run at the frequency and latency of the slowest DIMM. As an example, if one stick of PC3-1066 with timings of 10/10/10 is paired with two sticks of PC3-1333, the PC3-1333 will run at PC3-1066 speeds using that stick’s 10/10/10 latency.

How does it work?

We are at the point where enhancements to clockspeeds are not enough to satisfy the voracious appetites today’s most demanding applications have for system bandwidth. While just one of today’s DDR3 modules has enough bandwidth to transfer the contents of 18 CDs in a second (12800MB/s with DDR3-1600), we still need more.

Just as dual channel memory debuted to address yesteryear’s dearth of system bandwidth, tri-channel memory allows three sticks of DRAM to access a system’s memory controller at the same time. This technique, called parallelism, enhances performance without significantly adding to the cost or complexity of the system.

Other examples of the benefits of parallelism can be found in dual core CPUs, quad core CPUs, RAID arrays for hard drives, and even in the fire department’s decision to bring more than one hose. It’s clear that performing tasks in parallel can often be more beneficial than doing them with a single, larger device. Why let the back of the house burn down when you’re quelling the fire in the front?

How to buy tri-channel memory

It is important to keep in mind that tri-channel is not a feature granted to memory modules. Rather, tri-channel capabilities are strictly governed by the chipset featured on a motherboard. In theory, any three modules of an identical speed and capacity will properly function if paired in a tri-channel configuration on any chipset that supports this feature.

Practically speaking, however, most performance memory manufacturers are now selling convenient 3x1GB or 3x2GB kits of memory which can arm the Core i7 with up to 12GB of DRAM. Helping to avoid bizarre issues that untested sets can unleash, these modules have been factory-tested for compatibility.

Wrap-up

Remember that — with no exceptions — can x86-32 editions of Windows address and use more than 3.2GB of memory. While those 3x2GB kits are deliciously tempting, be sure you’re running a 64-bit edition of Windows so the new capacity is not wasted on the limitations of 32-bit’s aging addressing scheme.

Three identical sticks of memory installed to talk to the memory controller at the same time: it’s that easy! While DDR3 carries a price premium over our beloved DDR2, the increasing availability of Core i7 systems is sure to reduce the price over time.

Comments

  1. Marco Saillant
    Marco Saillant I need to know if it is the same to use ddr3 dual or ddr3 tri in memory slots.
  2. Thrax
    Thrax To use dual channel you need to install 2 sticks of memory. The two sticks must be installed in DIMM#2 of channels A and B.
  3. RWB
    RWB Thanks Thrax, i had seen kits at newegg recently but becuase I dont have a computer anymore or internet at home or work(i have to use my phone like now) I figured it was a gimmick and didn't look into it. This is definitly a nice new toy to play with whenever i can get back on my feet ;)
  4. Thrax
    Thrax I have updated this guide to be more specific regarding possible tri channel configurations, and I have also added information regarding dual channel.
  5. Barsju
    Barsju Thanx for a very nice and to the point guide! Just one question though. Does "All modules should be of the same capacity" mean that it is not possible to run a 3x2GB + 3x1GB = 9GB configuration? Or does it simply mean that you must have the same capacity within each of the 2 DIMM channels?
  6. tomas
    tomas I also very confused on this. On your table, 4 dimms will work in tri-channels. How about 5 dimms? If I use 3*2GB+2*1GB, will it work on tri-channels?

    Also, how to see if the memory working in tri-channels? Can CPUZ->SPD judge this?
  7. Thrax
    Thrax Five sticks is an unsupported memory configuration for the X58 chipset and may yield unpredictable results. You will certainly not get tri-channel. You might get dual channel with that configuration.

    CPU-Z > memory tab will reveal the current, running configuration.
  8. alex
    alex hi i would like to ask can i upgrade my 4gb (2x2gb) dual channel ddr3 ram to tri-channel by buying and adding one more stick of 2gb ddr3 to the current 4gb set? and must the speed and latency of the 3 rams to be same to work?
  9. Thrax
    Thrax Yes, if you follow the three DIMM installation procedure listed in the article, you can get tri-channel working on your system. It is IDEAL that all the memory be the same speed, but it's not required.
  10. alex
    alex so after i installed another stick to my 2x2 4gb ddr3 it will detect the tri-channel itself or do i need to change anythings in the bios?

    thanks ^^
  11. Thrax
    Thrax It will do it automatically. :)
  12. Jack Gilvey
    Jack Gilvey Great stuff!

    How is that 4th DIMM used in tri-channel?

    I've order a refurb Dell Studio XPS (Core i7 920) that comes with 4 1GB DIMMs. If the BIOS doesn't recognize 4 as tri-channel (it's listed as dual in the specs), am I better off re-purposing just 3GB in tri-channel?
  13. navid
    navid I am planning to buy an Intel DX48BT2 motherboard. What if I wanted to use up to 8GB of RAM, what would be the best to do to take advantage of the dual or the tri channels feature? Is it possible to combine 4x 2GB dual channels and be able to actually use this feature? Based on your article, I guess buying 4x 2GB tri channel would not make sense, right?
  14. BuddyJ
    BuddyJ X48 only does dual channel.
  15. tufftaeh
    tufftaeh I have 8GB RAM (2x2GB + 4x1GB) in my Dell Studio XPS 435. Can this really run in tri-channel (as CPU-Z states)?
  16. TC Soon
    TC Soon My Dell XPS 9000 comes with 2X2GB & 1X1GB (total 5GB). In order to activate the Tri channel I add 1X2GB & 2X1GB making a total of 9GB. According to your digram the the ram must be paired with each and other. That is to say I have to fix 1X2GB and 1X1GB as a set at DIMM 1&2 ? Thank you
  17. Shipy2002
    Shipy2002 hey just bought a system heres the specs that you may need to know

    Intel® Core™ i7 930 Quad Core Processor (2.80GHz,8MB Cache) - LGA1336
    Microsoft® Windows® 7 Home Premium
    700W PSU
    ASUS P6T SE Mainboard - Intel Coreâ„¢ i7 & i7 Extreme Edition - ATX
    8GB 1333MHz Dual Channel DDR3 SDRAM - ( 4x2GB )

    Now heres my question . The 8gb of ram is running at dual channel which is fine for now , however could i just buy another 2x2gb of the same ram put it in and bish bash bosh it will be running at tri-channel ? as all the 6 slots will be taken up . Or do i have to do something in the bios ?

    One further question .. could I run tri channel with the 8gb(4x2) by just changeing the position of the ram as in the guide?
  18. Paul
    Paul "Remember that — with no exceptions — can x86-32 editions of Windows address and use more than 3.2GB of memory"

    No exceptions? Baloney. Check out Windows Server 2000 Enterprise and Dataserver editions. Same for the 32 bit version of Windows Server 2003 Enterprise & Dataserver. The use PAE. Look it up.

    I've seen patches for Windows 7 32-bit and Windows Vista 32-bit to enable PAE to use more than 4 GB, but, these are hacks, obviously unsupported by Microsoft.

    Why doesn't MS support PAE for consumer 32-bit OS'es? Don't know for sure. The "official" reason to my knowledge is that 32-bit drivers might not be tested in PAE and therefore work fine with 4 gigs or less, but not with more. Though I would think that certification of 32-bit PAE compliant drivers would be doable. The other reason is that MS wants people to move to 64-bit and therefore do not want to enable larger address spaces for 32-bit OS'es.
  19. Thrax
    Thrax We are well aware. We are, however, a consumer-oriented site. Those OSes and that information are not relevant to our readers or this topic. Thank you.

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