Behind the Core i7Core i7 and Memory Controller Detailsour review of the Core i7 processors, we have a brief re-cap of the major changes that the Core i7 has over the Core 2 series CPU.Ever since the introduction of the PC, the system memory has been located on a separate bus. This bus has been connected to the system using a dedicated chipset called a Northbridge. This chipset really was the heat of the system as it connected the CPU to the memory and to the other integrated and discrete components through different buses that the system had. Many of these buses included ISA, PCI, AGP and now PCIe.Back in 2003 AMD revolutionised the way the CPU and memory communicated. AMD's K8 processor integrated its DDR memory controller onto the CPU itself. The Socket 754 integrated a single channel DDR memory controller supporting up to 400MHz memory for a grand total of 3.2GB/s of bandwidth. The impressive part of this was that the CPU was able to use up to 3GB/s of the total 3.2GB/s and only 200MB/s was wasted on overheads. While impressive, it wasn't able to keep up with Intel using Dual Channel DDR memory, so Socket 939 popped up supporting an extra DDR memory channel, allowing for a grand total of 6.4GB/s memory bandwidth. When tested, 6.12GB/s was available with only a little wasted on overheads and the rest of the system. AM2 popped up later on supporting DDR2 memory on a dual channel basis, giving up to 8.5GB/s total with around 7 to 7.5GB/s available depending on the speed and latency of the DDR2 modules.Intel's Core i7 is the first generation CPU from Intel to have an integrated Northbridge on the CPU, which is known as the UNCORE. This is connected to the CPU through the request queue; this is the same bus/interface that all four cores use to communicate with each other as well as the level 3 cache. Rather than a single channel first generation such as AMD's first instance, Intel has gone all out. Three separate 64-bit memory channels have been set on the UNCORE for a grand total of a 192-bit memory interface. Further to this, Intel has abandoned DDR2 with Core i7 and goes with DDR3 memory rated for 1066MHz initially. With three channels of memory using this spec we get a total of 25GB/s memory bandwidth. This is shared amongst all of the cores along with the system and so far we have seen that up to 24GB/s can be claimed in tests.This is a huge amount of data that can be transferred between the CPU and the memory controller. However, does the system really need all this extra bandwidth? Can the system survive on two channels of DDR3 memory, leaving the system with 17GB/s to use?
Test System Setup and EverestTest System Processor: Intel Core i7 956 (24x133MHz)Motherboard: ASUS P6T Deluxe OC Palm (Supplied by ASUS)Hard Disk: Intel SSD X25-M80GB (Supplied by Intel)Graphics Card: GIGABYTE 9800GX2 (Supplied by GIGABYTE) Cooling: Stock Intel LGA1366 CoolerOperating System: Microsoft Windows Vista X64 SP1Drivers: Intel INF 126.96.36.1997, Forceware 178.24Today's tests are performed on a single board; we are pushing the limits with the memory system to determine whether or not DDR3 in triple channel will provide a huge benefit over running in dual channel mode. We have completed tests at both 1066MHz and 1600MHz XMP in dual and triple channel arrangements.EVEREST Ultimate EditionVersion and / or Patch Used: 2006Developer Homepage: http://www.lavalys.com Product Homepage: http://www.lavalys.comBuy It Here
Benchmarks - Sisoft SandraSiSoft SandraVersion and / or Patch Used: 2009Developer Homepage: http://www.sisoftware.co.ukProduct Homepage: http://sisoftware.jaggedonline.com/index.php?location=home&a=TTA&lang=enBuy It Here
Benchmarks - Adobe Premiere Elements 4.0Adobe Premiere Elements 4.0Version and / or Patch Used: 4.0Developer Homepage: http://www.adobe.com Product Homepage: http://www.adobe.com/products/premiereel/Buy It Here
Benchmarks - CrysisCrysisVersion and / or Patch Used: 1.1Timedemo or Level Used: Custom TimedemoDeveloper Homepage: http://www.crytek.com/ Product Homepage: http://www.ea.com/crysis/Buy It Here
Final ThoughtsFinal ThoughtsCore i7 is a remarkable CPU. Intel has really outdone itself on the Core series of CPU and not one has been a disappointment. Each time Intel has an iteration of it, there is more power and more features to surface.Core i7, while sharing the Core name is a whole different animal; fast, feature packed and designed for a totally new platform, making it Intel's big jump away from familiarization. One of the biggest things that everyone has been looking forward to with Core i7 was the removal of the aging and antiquated FSB, allowing the CPU to finally live up to its potential. And the integration of the memory controller onto the CPU was the biggest leap forward in performance of all. However, Intel really didn't need to worry about a triple channel memory controller at this stage.We have seen today that dual channel memory on the Core i7 is more than enough to keep it fed with bandwidth, especially since the CPU and memory are communicating with each other directly. There is very little lost bandwidth and it makes better use of all of the dual channel memory than the triple channel memory. However, with Intel's plans to increase speeds and allow heavier memory usage, especially with IGP based systems, the extra bandwidth will end up being welcomed.Our moral to this story is if you're planning on a Core i7 system, don't just go out and buy triple channel memory straight away. If your budget allows for it, then by all means more memory will help, especially in Vista. However, with today's results you can see that dual channel memory is more than capable of keeping up with the Core i7.
Last updated: Apr 7, 2020 at 12:27 pm CDT
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