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What is tri channel memory?
Robert Hallock
November 19, 2008 4:52 PM ET in Tech
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.
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.
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 3×1GB or 3×2GB 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 3×2GB 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.
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