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With an Intel I7-920 CPU -- am I wasting money buying DDR3 1600 RAM

AFTerry
AFTerry used Ask the Experts™
on
I just got a brand-new Gigabyte GA-EX58-UD3R motherboard with an Intel I 7-920 CPU. I went to the Gigabyte Website and checked out their approved list of triple channel memory RAM.

RAM above 1600 (i.e. DDR 3 1800) runs as one DIMM per channel only. DDR three 1600 runs as triple channel. I don't understand the technical difference. But I would like to.

But my question is, now that I have ordered two 6 GB (3 x 2 GB) OCZ PC3-12800  DDR#3 1600 triple-channel memory kits (OCZ3X1600R2LV6GK), which is approved on the gigabyte site, as tested triple channel memory. I have learned a blogger could not get his DDR 3 1600 modules to perform at that speed (using an Azus Motherboard with an Intel I7-920 CPU)

A representative of the RAM company defending the DDR 3 1600 modules wrote:
"we apologize for this inconvenience. however, the Intel I7 memory controller is not good to run with 6 modules installed. they need to have stronger single. if you use rated DDR3 1600 memory 6 modules, the best you can get is DDR3 1333. if you want to run DDR3 1600, you need to purchase DDR3 1800 or 1866 memory. there is nothing wrong with each memory modules, it just I7 doesn't support over DDR3 1066 if you check out the Intel I7 website."

http://www.intel.com/products/processor/corei7/specifications.htm

What should I do?  And why?  What will happen if I use the DDR3 1600 RAM, triple channel memory sticks, and even I should buy them, will I get a noticable bang for my buck by increasing to 1600 over 1333?  And what does "One DIMM Per Channel Only" mean?

Also, as an extra credit question, am I buying the right memory?  The OZC OCZ3X1600R2LV6GK memory is more expensive than similar, cheaper, G-Skill DDR3 1600 memory (that is not on Gigabytes list, but seems to be getting better reviews from G-Sill customers then the OCZ RAM is getting.

If I act fast enough, I could probably cancel the shipment of
OCZ:  1600MHz DDR3 CL 8-8-8-24 (CAS-TRCD-TRP-TRAS) 1.65 Volts
and get the
G-Skill: F3-12800CL9T-6GBNQ is 1600MHz and has CL 9-9-9-24 (don't know the voltage)
or find
great 1333 memory (by any maker you recommend)

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Gary CaseRetired
Most Valuable Expert 2013
Top Expert 2009

Commented:
The problem is simple:   With unbuffered RAM modules the signal degradation if you install 6 double-sided modules is really bad, so you either have to use slower modules;  increase the latency settings; bump up the voltage a bit;  or sometimes a combination of all three to get them to work with reasonable reliability.

The best solution is to NEVER install more than 3 double-sided modules on a triple channel board (or 2 modules on a dual-channel board).    That's why server motherboards use buffered RAM, which eliminates this problem (thus you can install as many modules as you want up to the board's capacity).

Back to your question:   If you want the memory system to run reliably and still want to use DDR3 1600 modules, then only install 3 modules.   If you want 12GB of RAM, use 3 4GB modules:  http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007611%20600006050%20600006078&IsNodeId=1&name=12GB%20%283%20x%204GB%29
Gary CaseRetired
Most Valuable Expert 2013
Top Expert 2009

Commented:
... on other comment:   You'll also have a more reliable memory subsystem if you buy modules that run at the DDR3 standard 1.5v      Your motherboard does allow adjusting the memory voltage, but this is not an SPD parameter, so you'll need to adjust it manually if you use modules that require a higher voltage (if you forget to do this, you may have unreliable memory operation).
Retired
Most Valuable Expert 2013
Top Expert 2009
Commented:
... while I'm writing this, I'll vent a bit: I REALLY wish the chipset makers would support buffered RAM on desktop chipsets. As systems migrate towards 64 bit CPUs, and home-based systems tend towards large amounts of installed RAM, it would be really nice if you could safely install as much as you want without concerns for bus loading. But the simple fact is that isn't the case, so if you want prodigous amounts of RAM you need to use a server-based motherboard with a Xeon CPU ==> you can still install a desktop OS (i.e. Windows 7) ... but then you can install as much RAM as you want :-)

Meanwhile, I consider 8GB the practical max for dual-channel systems (using 2 x 4GB modules) and 12GB the practical max for triple-channel systems (using 3 x 4GB modules).

... but 4GB modules are fairly pricey, so for many that translates to 4GB for dual-channel and 6GB with triple-channel, using the more affordable 2GB modules.

Note:   Your OCZ modules should work fine as long as you only install one kit (3 modules).

Author

Commented:
The "venting" was worth the price of admission... The cloud lifts and dust settles.  3 x 4 GB = 12 GB max in a tripple channel system (though costly) and keeping the RAM at 1.5v makes sense because that allows room to finagle.  I still don't understand what one DIMM per channel means, or if getting 1600 RAM is still preferable to 1333, but I have the idea that getting 1333 at 1.5 with tighter timings trumps 1600 at 1.65v being loose.  Right?
Gary CaseRetired
Most Valuable Expert 2013
Top Expert 2009

Commented:
One DIMM per channels means exactly what it says.    Your motherboard has 6 slots -- 2 per memory channel;  but if you install double-sided modules (any 2GB module will be double-sided) the loading on the address and data bus is simply too much to run at the higher speeds [the waveform is very degraded with that much loading -- you'd need an Oscilliscope to see it, but you can get an idea by watching item #10 here: http://www.corsair.com/memory_basics/index.html ]

That's why I recommend only using one module per channel.

There's really nothing wrong with using higher speed memory that requires a slightly higher voltage (e.g. 1600 at 1.65v) ... you just have to be aware that the memory requires the higher voltage and make the adjustment in the BIOS.    I've also seen some cases where the higher voltage modules have caused issues after several months at the higher voltages.    Personally, I always stay with the standard voltages (1.5v for DDR3).

Author

Commented:
garycase, thank you for your time and gift of experience, and the link.  No joke.  I took your advice and ordered:
  • G.SKILL Ripjaws Series 12GB (3 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Desktop Memory Model F3-10666CL9T-12GBRL
  • for an inexpensive 349 & tax.
My other affordable choice was
  • OCZ Reaper Edition 12GB (3 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Low Voltage Desktop Memory Model OCZ3RPR1333C9LV12GK  
  • for 349 & tax (marked down from $399, with a $30 rebate)
The reason I want with G.Skill is because of your 1.5v advice.
  • G.Skil 9 9 9 24      1.5v      $349 plus tax or $384.11
  • OCZ   9 9 9 20      1.65v    $349 plus tas or $384.11 (with a $30.00 rebate)
I hope I did well taking the G.Skil over the OCZ.
  I had ordered, from Amazon, but am sending back:
  • OCZ DDR3 1600 12GB
  • 2 packs of (3 x 2GB) or 6 modules
  • OCZ    8 8 8 24       1.65v                              $387.98 (all in).

Gary CaseRetired
Most Valuable Expert 2013
Top Expert 2009

Commented:
A good choice :-)

I've not used any G.Skill modules, but they get good reviews, and I'd expect it will work fine.    Once you install it, boot a copy of MemTest86+ and let it run for a couple passes (with that much memory I suspect that will be a couple hours or more) ... always a good idea with any new memory to give it a thorough test when you install it.
http://www.memtest.org/

That will be a VERY nice system :-)
Gary CaseRetired
Most Valuable Expert 2013
Top Expert 2009

Commented:
... I was going to look up the manual to tell you which 3 slots to install the modules;  but I'm sure you can do that -- HOWEVER, in doing so I noticed that the EX-58-UD3R has only 4 memory slots [a weird combo for a triple channel board]  ==> but the X-58-UD3R has six slots (the board I had assumed you had).

Which model do you have?

Author

Commented:
Garycase, I was going back over answered questions and I found this gem. I can't believe what I'd paid back then!

If you get a chance look at my new question on upgrading from the G skill modules to Corsair dominator.  Thanks for the years of good health and help.
Gary CaseRetired
Most Valuable Expert 2013
Top Expert 2009

Commented:
"...  I can't believe what I'd paid back then! ..."  ==>  Computing gear these days is practically FREE ... or at least it seems that way to some of us old-timers.

... I once bought an 8KB memory card (not a typo) for ~ $1200 => and that was a $200 savings over the assembled price, so I had to solder all the sockets and chips on the board (an early S-100 computer)

... My first hard drive held 26MB (also not a typo) ... and I got it for 10% off -- so it only cost me $4500