Big Question

[Tradesman]

In the DDR3 forum you provided the following response to a user asking about running 12GB, wher you suggest against running 6 sticks, you do the same quite often with DDR2 and running 4 sticks. I posted a reply also shown below, and rather than tie up the other users thread, thought this should be separate. My response is based on working with systems for some 25 years now. Am I totally off base here with my explanation or is your response off base. I can provide a number of reference material from which I gleaned my knowledge of how dual channel/memory controllers/chipsets/etc work. Have I been wrong all this time, mislead by Intel, among others?

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GSKILL TECH
Administrator

Join Date: Jul 2008
Posts: 117

well, i would not recommend to run 6 modules. it is not just the heat issue.
the problem is the memory controller.
tri-channel memory controller has a very weak channel. YEAH, YOU SEE EVERY MOTHERBOARD WANTS YOU TO USE 1-3-5 OR 2-4-6. why? because other channel is WEAK.
if you want to use 6 modules, you might need to

1. increase the QPI volt. (make memory controller stronger)
2. increase the memory volt (make memory signal stronger)
3. decrease the speed of memory. (prevents memory controller overload)

NO3 is the best way to do because 1 and 2 might cause overheat problem





Join Date: Feb 2009
Posts: 96
Default
Actually on most mobos, say with 4 RAM slots (P43, P45, most chipsets), SLOTS 1 and 2 are physically connected to Channel A, slots 3 and 4 are physically connected to Channel B. Each Channel has 64 bit access, hence when you install in slots 1-3 or 2-4 you are putting a stick in each channel thus enabling DUAL-CHANNEL mode or 128bit access. There is nothing to do with a 'weak' channel.

Also note, I used the 4 slot boards as an example, because the excuse you offer above about tri-channel is the same exact thing you tell people all the time about dual channel have a 'weak' controller.

If what you are saying is true, then what is the 'weak' channel? is it channel A or Channel B, particularly in light of the fact you NEED both channels to run DUAL-Channel and get the 128 bit access

Would appreciate a reply.

[G.SKILL]

we have replied you in the original thread, please check it
any advice is welcome


G.S

[Tradesman]

Reply to other thred

Below is my replyI posted on the other thread for those interested:

I realize that the CPU contains the memory controller, but disagree on your explanation of channels, the architecture is similar to dual channel, except for there are channels A(1-2), B(3-4), and C(5-6), hence slots 1-3-5 and 2-4-6, essentially the same as dual channel, but with as additional channel, this allows for 192 bit access vs 128 in dual channel. Even at this with today's mobos, it has not reached the limits of the memory controller inside of the i7 series. It is entirely feasible under the specs for the i7, and how it is designed, to run 9 slots instead of the common 6. Unfortunately the X58 chipset is still experiencing growing pains, thus the continued BIOS upgrades by the various manufacturers.

Bellow is possibly a better explanation:

With the coming of Core i7 we've seen the integration on-CPU integrated memory controllers for DDR3 SDRAM with 1 to 3 -- 64-bit memory channels (physically four only three active though). You read it right, a tri-channel memory controller. Therefore total memory bus width goes up from 128 bits to 192 bits allowing a massive bandwidth increase as they ar no longer tied to the FSB.

Intel eliminated those "FSB brakes" by designing Nehalem's architecture to use 64-bit memory controllers which are connected directly with the processor's silicon. As a result this new design should bring a bandwidth utilization of as much as 90%, a nice jump from today's 50-60% utilization for sure. The new controller of course supports both registered (server market) and unregistered (consumer) memory DIMMs. The controller is fast ... very fast, and supports DDR3-800, DDR3-1066, DDR3-1333 JEDEC standards, yet has room for future scalability. The memory controller is able to handle 64GB/s, a full tri-channel DDR3-1333 implementation will only amount to 32GB/s maximum bandwidth utilization.

Do the math and conclude that even DDR3-2000 will not max out the controller.

So then, three memory channels per processor, each channel supports a maximum of 3 DIMMs. Again do the math and a single processor can support a maximum of 9 memory slots. You are of course free to use one or two DIMMS, but for optimal performance, the minimum would however be three, one DIMM per channel. So depending on the motherboard class of use, the board can come configured with three, six or nine memory slots.

[GSKILL TECH]

DDR2 and DDR3 are different. don't mix those two

[jack00980]

My response is based on working with systems for some 25 years now.

i read all ur posts, doesn't look like u have 25 yrs of exp.

[Tradesman]

To Gskill,

Don't understand your response - nothing was said about mixing DDR2 and DDR3. You do repeatedly say with both dual and tri channel that both have a 'weak' channel yet with dual channel RAM you have to have a stick in each channel, same with tri, a stick in each channel, so I'm just trying to understand where this 'weak channel' is you speak of.

[Tradesman]

To jack00980,

Just trying to get gskill to explain why most every time anyone has problems running more than 2 sticks of RAM the want to blame it on a 'weak channel' or a 'weak' memory controller. For instance on, say a P45 mobo (dual channel - DDR2), there are 2 channels - Channel A, which occupies slots 1-2 and Channel B which occupies slot 3-4, to get the full bandwith of dual channel you need to pair up your sticks in 1-3 or 2-4 to get 128 throughput. If you put two sticks in 1-2, it will work, albeit at 64.

Here's a decent article about how Dual Channel works:

http://www.hardwaresecrets.com/article/133/1

[GSKILL TECH]

To Gskill,

Don't understand your response - nothing was said about mixing DDR2 and DDR3. You do repeatedly say with both dual and tri channel that both have a 'weak' channel yet with dual channel RAM you have to have a stick in each channel, same with tri, a stick in each channel, so I'm just trying to understand where this 'weak channel' is you speak of.

tri channel is for ddr3, dual channel is for ddr2 and ddr3. you question is mixing the DDR2 and DDR3 memory controller.

let me tell you this.

nvidia 680i / 650i claims they can run DDR2 1066.
yes if you have DDR2 1066 in one channel.
but 4 modules can only run at DDR2 800 or 667.
you know why? it is because their memory controller is no good.
when you have both channel fill with memory, you are stress out the memory controller.
if motherboard is very well design, the signal is strong enough for cpu to read.
but most the case, NO this is not happening to all the motherboard.

also the layout of the motherboard makes different
one channel has longer line (i don't know what is correct term) than other channel.
short line to memory controller has better signal and that calls stronger channle.

memory controller can handle DDR2 800 4 sticks very good now because the technologe of NB
but one the speed of memory increase, memory controller cannot handle it more. so for DDR2 1066+ to DDR3 1333, MC can only handle one channel well but not both channel.

[Tradesman]

No I haven't questioned mixing the DDR2/DDR3 memory controller? I simply explained how dual and tri channel work.

Interesting you bring up the 680i, I have an XFX 680i mobo, 2 8800 GTSs, an E8500 CPU, setup w/ 4x2GB 1066 OCZ and it runs just fine, sees all 8GB (at stock timings and voltage, except when OCing), have also run 8GB 1066 on ASUS 680i's before on a few builds.

[GSKILL TECH]

No I haven't questioned mixing the DDR2/DDR3 memory controller? I simply explained how dual and tri channel work.

Interesting you bring up the 680i, I have an XFX 680i mobo, 2 8800 GTSs, an E8500 CPU, setup w/ 4x2GB 1066 OCZ and it runs just fine, sees all 8GB (at stock timings and voltage, except when OCing), have also run 8GB 1066 on ASUS 680i's before on a few builds.

wooow that is good to hear. want to share your 8GB setup to us and we will love to check it out. cuz even DFi, Evga, Asus, Gigabyte RD cannot make it work

[jack00980]

No I haven't questioned mixing the DDR2/DDR3 memory controller? I simply explained how dual and tri channel work.

Interesting you bring up the 680i, I have an XFX 680i mobo, 2 8800 GTSs, an E8500 CPU, setup w/ 4x2GB 1066 OCZ and it runs just fine, sees all 8GB (at stock timings and voltage, except when OCing), have also run 8GB 1066 on ASUS 680i's before on a few builds.

dude Tradesman if u like ocz just go there ask TONY LOL

[Tradesman]

Originally the 680i was rated to 800 on the factory boards since that was the highest rated RAM by JEDEC Standards, then as the designs and BIOSs matured the front side bus (originally 1066) was upped to run at 1333, JEDEC put out 1066 Standards and the RAM ratings went up to 1066 (1200 in some instances) - it was then that some (not all, not sure if Gigabyte of the 680i mobos started taking the higher RAM i.e. the Striker (ASUS), the LanParty NF680I (DFI), also heard that others have run 1066 on the MSI P6N Diamond, but I personally haven't), XFX, EVGA and BFG, the boards I primarily used and built with are shown below:

http://www.xfxforce.com/en-us/produc...ies/680.aspx#2

http://www.evga.com/support/motherboard/

http://www.bfgtech.com/bfgrinf680is.aspx


As with any mobo, it might take some tweaking, but generally you can get 8GB to work (with Intel anyway), AMD is another story.

It's interesting you choose to pick on nVidia, which has been noted for a weak controller in the early 680i chipset, but you also provide the weak controller excuse on many other motherboards of different chipsets as to why people can't get 8 or more to work, i.e. P35, 43, 45, etc. yet people get them to work.

I would think with the current trend in systems towards 64bit computing and the use of more RAM, you would be testing your RAM in higher quantity configuration. Seems most of the support requests revolve around 8GB or more setups.

Also could cite an available technical reference as to what you are talking about when you say one channel is weaker than another, particularly in light of the fact for dual channel to work you HAVE to have a DIMM in each channel. See the Intel doc below

http://www.intel.com/support/motherb.../cs-011965.htm

[Tradesman]

Jack

As a matter of fact, I do like OCZ, also Mushkin, Corsair, Kingston and GSkill, not real thrilled with Patriot or Geil. Never dealt with a Tony, there's a Sean in tech support I've dealt with via e-mail/telecon that is rather well versed in their RAM, he's the one that suggested their SLI Ready series for the 680i boards, their Fatality series also worked well with the 680i boards.