Core i7 Memory Performance and Choices

Core i7 Memory Performance and Choices

When the Core i7 was released weeks ago, the new triple-channel memory feature was a big shock to everyone.  Also shocking was the 1.65V limit set forth by Intel.  Thus, all memory on the market was unfit for use and everything we learned from the Core 2 line had to be relearned for Core i7.  Thus, this article will try and explain how the memory subsystem works and how to choose the best memory for your intended computer application.

Relearn the Memory

Everything we know about the Core 2 line is different in terms of memory.  Here is a basic outline of what has changed.

Integrated Memory Controller - There is no more FSB.  The Northbridge is now just a glorified PCI-E controller used to connect to the video cards.  Thus the task of controlling the memory now lies with the processor.  However this is much better as memory bandwidth is much improved and timings make more difference then ever before.

Triple Channel - With triple channels, bandwidth is almost 3x to 4x higher then in previous generations.  Also, now greater ranges of memory capacities can be added then ever before.  This means there is a memory kit to fit your budget and application.

Voltage Limits - Intel has stated that the DDR3 memory must operate at or below 1.65 volts.  Most DDR3 memory on the market was operating at around 1.8 volts, which meant it could not be used with the new processors.  However, many memory manufacturers jumped aboard quickly and there are now literally dozens and dozens of memory kits available.

Timings Mean Everything - Timings now mean more then the actual frequency of the memory.  Due to the direct connection, memory running at 1066 MHz can outperform 1600 MHz memory if the timings are aggressive and if the application at hand does not need massive bandwidth.

Performance Benchmarks

I know, you guys are begging for some memory benchmarks.  Here are some benchmarks previously done to see what memory works best.  Please click on any image to show a bigger image.

Memory Benchmarks - Sandra 2009   Sandra shows some big bandwidths compared to the Core 2 line and some great latencies as well.  The lowly 800 MHz memory at around 16 GB/s even beats the top Core 2 bandwidths by almost 50%.  While this performance seems amazing, it makes almost no difference later on.

 

Gaming Benchmarks - 3DMark Vantage   While many people dispute the reputability of 3DMark, fact is, it is pretty consistent.  Otherwise we would have to test 30+ games to get a true feel of 3D capabilities.  As you can see, memory makes no effect at all in relation to memory.  It is the connection between CPU and GPU that matters along with what CPU and GPU.  Thus like in real games, memory makes almost no effect.

 

3D Rendering - 3DS Max 2009 and POV-Ray 3.7   As with our gaming benchmarks, the OpenGL based 3D design studio programs were not able to take advantage of the higher bandwidths.  Instead, there was only slight differences which many people would not notice.

 

Media Encoding/Decoding - ProShow Gold and Sandra Multi-Media   Again there is little difference in relation to the memory.  ProShow did show some difference, but not by much.  It may be a few more years before programmers can take direct advantage of all the extra bandwidth headroom.

The general consensus is that the new memory bandwidths are too high to be taken advantage of.  Until programmers come out with different applications to take advantage of Core i7 bandwidth, there is no reason to use extreme memory frequencies.

What Memory To Use

According to a previous article that can be found here, the 920/940 processors cannot use above 1066 MHz and the 965 cannot use higher then 1800 MHz.  However, certain motherboards were able to bypass those Intel restrictions and OC locked multipliers.  However, we cannot know for certain if a 920/940 CPU can safely run those frequencies for extended periods of time.  Only time will tell if they last.

Another thing to note is that Intel does not recommend fully populating all 6 DIMMs when using Intel XMP memory or running memory at 1600 MHz and above. 

32-bit OS Systems:

32-bit operating systems cannot see more then 4GB of memory.  Thus you must use only 3GB (3 x 1GB) kits at any speed rating that you desire.

 

64-bit OS Systems:

Depending on the OS, you may be limited to how much memory you can use.  These limits were taken directly from Microsoft. Windows XP 64 - 128 GB Windows Vista Home Basic 64 - 8 GB Windows Vista Home Premium 64 - 16 GB Windows Vista Business 64, Ultimate 64 - 128 GB   We recommend 6 GB with most Vista 64 installations that encompass any sort of performance applications (CAD, Gaming, Database).

 

Gaming:

As stated above, memory bandwidth makes no difference at current gaming technologies.  Software will not be able to take advantage of this for at least a few more years, so you can rest assured you will not be limited by memory for quite some time.  Please be aware recommendations are also including the fact that many gamers like to tweak or overclock by moderate amounts.  Games will see more of a benefit from tighter timings more then higher frequencies.   Recommended for 920/940:  1066 MHz  7-7-7-21 (Stock)  1333 MHz 9-9-9-24 (OC) Recommended for 965:         1333 MHz 8-8-8-24 (Stock)  1600 - 1800 MHz  9-9-9-24 (OC)

 

Overclocking:

If you are trying to overclock, you will want to stay away from aggressive timings and memory that requires higher voltages so that you can overclock higher without over-volting.  These recommendations are for the serious Enthusiasts who regularly overclocks higher then 20%.  Also, please use only 3 DIMM kits as overclocking ability is hindered when all slots are filled.  To maintain stability, it is also recommend to use a 3 GB (3 x 1GB) kit as the lower capacity modules put less stress on the system as well.   Recommended for 920/940:   1333 - 1600 MHz  9-9-9-24 @ 1.5V Recommended for 965:          1800 - 2000 MHz  9-9-9-24 @ 1.6V

 

3D Cad or Workstation:

Depending on your application, higher bandwidth may lead to an increase in application performance.  Also, to keep the system stable, we do not recommend overclocking on your system.  Tight timings will also lead to an increase in performance as well.  Please keep in mind that Intel recommends 1333 MHz and below when using all memory slots. Recommended for 965:          1333 MHz 9-9-9-24 (12, 24 GB)       1600 MHz 9-9-9-24 (6 GB)

 

Office or Home Desktop:

Going with Core i7 at the moment is overkill for any standard office or home desktop.  The Core i7/X58 combination of hardware is currently targeted for high-end users and gamers.  However, this the following recommendation for this system type. Recommended for 920/940/965:  1066 MHz  9-9-9-24