question regarding ddr dual channel mode

thenewguy001 · Jan 17, 2008, 03:31 PM

Can a system run in dual channel mode if you are using an odd number of memory modules? or do you need to have matching (capacity/speed/timing) modules on both slots of each memory bank that is occupied on your mobo? Does this vary from mobo to mobo?

Specifically, I'm wondering if a system can run in dual channel mode if you have two sticks of 512mb and one stick of 1gb.

Thanks in advance!

Zelig · Jan 17, 2008, 03:39 PM

Quote:

Originally Posted by thenewguy001

or do you need to have matching (capacity/speed/timing) modules on both slots of each memory bank that is occupied on your mobo?

Bingo. All modules must be running at the same speeds and timings. Sticks in a dual channel arrangement must be the same size.

So there's no combination of 3 sticks that can be run in dual channel.

IEMC · Jan 17, 2008, 03:40 PM

You need to use 2 EXACTLY the same sticks of memory. Same timings, capacity, company, etc.

Dual channel isn't necessarily great, either. Simply having 2 gigs is enough for a performance change.

mike2h · Jan 17, 2008, 03:52 PM

dual channel sticks should be purchased in kits. & im not convinced that performance of 1 gb dual channel(meaning i would go with i gig dual but it is debatable depending on your setup & usage) vs 2gb single channel is effective either. especially if they have different chips on the modules.

thenewguy001 · Jan 17, 2008, 04:12 PM

That's what I thought. Someone mentioned to me that one set of memory banks (512+512) can be set to run in dual channel, while the other memory bank (1gb+empty) can simultaneously run single channel on the same system. My understanding is that to achieve dual data rate you need to have both slots occupied, and if not, the memory controller will operate at the slowest module data rate, which is the single channel bank. Correct me if I'm wrong?

Thanks for the quick replies

CDsDontBurn · Jan 17, 2008, 04:24 PM

actually, you can run dual channel mode with mixed sticks. but they have to be of the same capacity still. for optomized performance, you need to buy a memory kit.

mike2h · Jan 17, 2008, 05:07 PM

Quote:

Originally Posted by CDsDontBurn

actually, you can run dual channel mode with mixed sticks. but they have to be of the same capacity still. for optomized performance, you need to buy a memory kit.

while this is mostly true, it does not always work & can create problems from very minor to non working due to variances in mb, chipsets & mem chips. but basically as long as speed, timings, & volt are (set)all the same it will work.

& newguy you got it right on the nose

CDsDontBurn · Jan 17, 2008, 09:32 PM

@ mike: sorry for the lack of details in my previous post. i was at work whe i made the post

. now i'm at school posting from my smartphone

mike2h · Jan 17, 2008, 11:14 PM

lol, no worries we are all just trying to help. you are doing a better job than i would under those circumstances.

PangingJr · Jan 18, 2008, 01:17 AM

Quote:

Originally Posted by thenewguy001

Can a system run in dual channel mode if you are using an odd number of memory modules? or do you need to have matching (capacity/speed/timing) modules on both slots of each memory bank that is occupied on your mobo? Does this vary from mobo to mobo?

Specifically, I'm wondering if a system can run in dual channel mode if you have two sticks of 512mb and one stick of 1gb.

Thanks in advance!

answer to your question is, yes, you can run the system memory in a Dual Channel Asymmetric mode if your motherboard's chipset supports the memory configuration. however, your system will not achieve maximum performance.

below is an example of a chipset that supports the memory configurations.
taken from Intel 965 Express Chipset Family Memory Configuration White Paper.
- For the Intel® 82Q965, 82Q963, 82G965 Graphics and Memory Controller Hub (GMCH) and Intel 82P965 Memory Controller Hub (MCH).
July 2006.

this information may have been updated from the information that i have with me now.

Quote:

Memory Organization and Operating Modes

The (G)MCH memory interface is designed with Intel® Flex Memory Technology so that it can be configured to support single-channel or dual-channel DDR2 memory configurations.
Depending upon how the DIMMs are populated in each memory channel, a number of different configurations can exist for DDR2:

• Single Channel – only one channel of memory is routed and populated, or if twochannels
of memory are routed, but only one channel is populated; can be either
channel A or channel B.

• Dual Channel Asymmetric – both channels are populated, but each channel has a different amount (MB) of total memory.

• Dual Channel Symmetric – both channels are populated where each channel has
the same amount (MB) of total memory.

The following sections explain and show the different memory configurations that are supported by the Intel 965 Express chipset family.

Single-Channel
The system will enter single-channel mode when only one channel of memory is routed on the motherboard, or if two-channels of memory are routed, but only one channel is populated. In this configuration, all memory cycles are directed to a single channel.

<pic>

Dual-Channel Asymmetric
This mode is entered when both memory channels are routed and populated with different amounts (MB) of total memory. With the aid of Intel Flex Memory Technology this configuration allows addresses to be bounced between channels in interleaved mode until the top of the smaller channel’s memory is reached, allowing for full dual channel performance in that range. Access to higher addresses will all be to the channel with the larger amount of memory populated; thus giving single channel performance through those addresses.

<pic>

Dual-Channel Symmetric
This mode allows the end user to achieve maximum performance on real applications by using the full 64-bit dual-channel memory interface in parallel across the channels.
The end user is only required to populate both channels with the same amount (MB) of total memory to achieve this mode. The DRAM component technology, device width, device ranks, and page size may vary from one channel to another. Addresses are bounced between the channels, and the switch happens after each cache line (64-byte boundary). If two consecutive cache lines are requested, both may be retrieved simultaneously, since they are ensured to be on opposite channels.

System Memory Mode Styles

<pic>

Mixed DRAM Memory Speeds
The (G)MCH will accept mixed DDR2 speed populations, assuming the SPDs on the DIMMs are programmed with the correct information and the BIOS is programmed as outlined in Intel’s BIOS reference code.
In all operating modes (Single-Channel, Dual Channel Asymmetric, and Dual-Channel Symmetric) the frequency of the System Memory will be set to the lowest frequency with its supported speed bin timings of all DIMMs populated in the system, as determined through the SPD registers on the DIMMs. For example, a DDR2-667 DIMM with supported 5-5-5 speed bin timings installed with a DDR2-533 DIMM with supported 4-4-4 speed bin timings should run at 533 MHz with supported 4-4-4 speed bin timings. The DDR2-667 DIMM should downshift to DDR2-533 timings, thus allowing the system to run at 533 MHz with supported 4-4-4 speed bin timings. The DDR2-667 DIMM will only downshift to DDR2-533, if the timings for DDR2-533 are programmed in the DDR2-667 DIMMs SPD.

Matth · Jan 19, 2008, 12:00 PM

In the Intel chipset documentation, equal capacity but unequal physical configuration (eg. 2x 512MB on one channel and 1 x 1GB on the other), is a SYMMETRIC mode. Other chipsets may not be so accommodating.

With the Intel chipsets, a machine with 1GB as a pair of 512's could be upgraded to 2GB with another pair of 512's, or by moving the two 512's to 1 channel and putting a 1GB on the other, with the possibility of upgrading to 3GB by returning to a 2 pair layout.

Quote:

Dual-Channel Symmetric
This mode allows the end user to achieve maximum performance on real applications by utilizing
the full 64-bit dual-channel memory interface in parallel across the channels with the aid of Intel®
Flex Memory Technology. The key advantage this technology brings is that the end user is only
required to populate both channels with the same amount (MB) of total memory to achieve this
mode. The DRAM component technology, device width, device ranks, and page size may vary
from one channel to another.

The accompanying diagrams show a fully paired 512 / 512 and a 256 + 256 / 512 configuration under "symmetric".

hakujin · Sep 14, 2008, 11:18 AM

Quote:

Originally Posted by Matth

In the Intel chipset documentation, equal capacity but unequal physical configuration (eg. 2x 512MB on one channel and 1 x 1GB on the other), is a SYMMETRIC mode. Other chipsets may not be so accommodating.

With the Intel chipsets, a machine with 1GB as a pair of 512's could be upgraded to 2GB with another pair of 512's, or by moving the two 512's to 1 channel and putting a 1GB on the other, with the possibility of upgrading to 3GB by returning to a 2 pair layout.

The accompanying diagrams show a fully paired 512 / 512 and a 256 + 256 / 512 configuration under "symmetric".

Old thread, but question for you. I plan to do exactly what you describe in your 1st example. I have an Abit IC7-G with 2 512MB sticks of Geil Ultra 3200 in dual channel in slot 1 & 3. I'd like to add a 3rd 1GB stick to slot 2 and continue with dual channel config symmetric. The chipset is Intel 875P / ICH5R. The Abit documentation would lead one to believe that both slots must be occupied for dual channel functionality, but if I leave the 2 sticks of 512 Geil and get a gig of Corsair PC3200 willl dual channel stay in tact?

Thanks in advance!

**temeteus82** · Sep 14, 2008, 11:38 AM

Quote:

Originally Posted by hakujin

The Abit documentation would lead one to believe that both slots must be occupied for dual channel functionality, but if I leave the 2 sticks of 512 Geil and get a gig of Corsair PC3200 willl dual channel stay in tact?

As the documentation says you will lose it. The bus width is 64-bit for single slot. When it Dual-Channel mode the bus width is 128-bit (64-bit + 64+bit) and to remain in Dual-Channel mode you would need to ad two sticks. But if I were you I would get 2x2gig kit and sell the 512MB sticks ...

hakujin · Sep 14, 2008, 11:42 AM

Quote:

Originally Posted by temeteus82

As the documentation says you will lose it. The bus width is 64-bit for single slot. When it Dual-Channel mode the bus width is 128-bit (64-bit + 64+bit) and to remain in Dual-Channel mode you would need to ad two sticks. But if I were you I would get 2x2gig kit and sell the 512MB sticks ...

So the intel chipset info about symmetric mode with equally sized channels (but one stick on one channel) is wrong? should that not supersede the more arbitrary abit info I scooped off a mainboard review website.

I would most definitely not want to do 2 2GB sticks... that's just a waste in a 32bit XP environment for me. I have a hard enough time rationalizing 2GB on my older system... it does fine with 1GB really, it's just with Firefox 3.01 it can get to around 90% memory utilization when running my regular stuff plus it and media center, on MCE 2005. Gaming is not an issue as my system isn't going to run Crysis any time soon, but does well @ 1280x720 for Bioshock, all Half Lifes, Spore, Fear, C&C Tiberium Kane Ed., Portal etc. with a Nvidia 6800 Oced and I'm not really look for much more in terms of PC games as I have a 360 and Wii.

I'm also wondering if the performance increase from dual channel is negligible, though the thing that concerns me are the SPD timings of my Geil causing a problem with a differing stick... would that be problematic?

My Geil advertises CL2-3-3, but in actuality only runs stable at 2.5-4-4 (even SPD is not 2-3-3, they're crooks).

Thanks for your reply.

cozumel · Sep 14, 2008, 12:29 PM

Hi hakujin and welcome to DriverHeaven.

I think temeteus meant to say better getting 2x1GB and sell the 2x 512MB. The memory controller on your board will prefer this, plus it keeps everything dual channel which increases your transfer speed.

As far as noticeable difference is concerned, why don't you set up your current 2x512MB modules so they no longer run in dual channel and do a direct performance comparison in the real world?

**temeteus82** · Sep 14, 2008, 03:04 PM

Quote:

Originally Posted by hakujin

So the intel chipset info about symmetric mode with equally sized channels (but one stick on one channel) is wrong? should that not supersede the more arbitrary abit info I scooped off a mainboard review website.

Well the equally sized channels needs paired sticks of RAM as far as I know it. So odd number of sticks won't work in dual channel mode.

Quote:

Originally Posted by cozumel

I think temeteus meant to say better getting 2x1GB and sell the 2x 512MB. The memory controller on your board will prefer this, plus it keeps everything dual channel which increases your transfer speed.

Correct I meant 2x1GB sticks.

**kris23** · Sep 14, 2008, 03:09 PM

the only way the above statement would work is in newer boards that support ASYMMETRIC DUal-Channel..... and that only works in P35 chipsets and newer as far as i know....

**Mousey** · Sep 14, 2008, 04:00 PM

Quote:

Originally Posted by kris23

the only way the above statement would work is in newer boards that support ASYMMETRIC DUal-Channel..... and that only works in P35 chipsets and newer as far as i know....

I wouldn't be so sure of that, i got Asymmetric dual channel on my old Abit IL9Pro which was the 945p chipset

**kris23** · Sep 14, 2008, 04:46 PM

9 series intel chips too? sounds right

but theres definitely no assymetric dual channel in the old 8 series chips

Matth · Sep 15, 2008, 05:50 PM

http://download.intel.com/design/chi...s/25273001.pdf
Definitely, no asymmetric dual - use this link Intel® 875P Chipset Memory Configuration Guide White Paper if it refuses to go directly to the PDF.

The 8 series offers single channel, "virtual single channel" (both channels loaded, not with a dual combination), dual channel (normal mode) and dual channel (dynamic mode).

Dynamic mode is a bank switching performance optimization possible only when all modules are identically banked (same capacity, sides, page size).

Dynamic mode will never be possible for two differently sized pairs, and depending on the architectures, might be possible for two same sized but non-identical pairs.

It will be possible for matched pairs and quads, with a quad apparently giving the best performance under dynamic bank switching

hakujin · Sep 24, 2008, 09:46 PM

Pardon my delay. Thanks for all the info, it is appreciated, and noted. I decided to sell the Geil Ultra Dragon 3200; sold 2 512MB sticks for $22 on Craigslist, and purchased 2 1GB PC3200 Corsair Value Select sticks for $25 after rebate. Now I feel ike I have more than I know what to do with. Unlike my wife's Vista laptop which gobbled up the extra gig, it seems in MCE that I'm not fully utiizing it, but at least no more 90%+ RAM usage, and it's dual channel symmetric... who said DDR, HT, and Netburst is dead.

Jan 17, 2008, 03:31 PM	#1
thenewguy001 DriverHeaven Junior Member Join Date: Dec 2004 Location: Canadian West Coast Posts: 76 Rep Power: 0 System Specs	question regarding ddr dual channel mode Can a system run in dual channel mode if you are using an odd number of memory modules? or do you need to have matching (capacity/speed/timing) modules on both slots of each memory bank that is occupied on your mobo? Does this vary from mobo to mobo? Specifically, I'm wondering if a system can run in dual channel mode if you have two sticks of 512mb and one stick of 1gb. Thanks in advance!

Jan 17, 2008, 03:40 PM	#3
IEMC Neighborhood screw up. Join Date: Dec 2005 Location: MI, US Posts: 710 Rep Power: 35 System Specs	You need to use 2 EXACTLY the same sticks of memory. Same timings, capacity, company, etc. Dual channel isn't necessarily great, either. Simply having 2 gigs is enough for a performance change. __________________

Jan 17, 2008, 03:52 PM	#4
mike2h DriverHeaven Extreme Member Join Date: Nov 2002 Location: norcal Posts: 6,489 Rep Power: 74 System Specs	dual channel sticks should be purchased in kits. & im not convinced that performance of 1 gb dual channel(meaning i would go with i gig dual but it is debatable depending on your setup & usage) vs 2gb single channel is effective either. especially if they have different chips on the modules. __________________

Jan 17, 2008, 04:12 PM	#5
thenewguy001 DriverHeaven Junior Member Join Date: Dec 2004 Location: Canadian West Coast Posts: 76 Rep Power: 0 System Specs	That's what I thought. Someone mentioned to me that one set of memory banks (512+512) can be set to run in dual channel, while the other memory bank (1gb+empty) can simultaneously run single channel on the same system. My understanding is that to achieve dual data rate you need to have both slots occupied, and if not, the memory controller will operate at the slowest module data rate, which is the single channel bank. Correct me if I'm wrong? Thanks for the quick replies Last edited by thenewguy001; Jan 17, 2008 at 04:23 PM.

Jan 17, 2008, 04:24 PM	#6
CDsDontBurn 127.0.0.1 Join Date: May 2003 Location: Southern California Posts: 21,849 Rep Power: 133 System Specs	actually, you can run dual channel mode with mixed sticks. but they have to be of the same capacity still. for optomized performance, you need to buy a memory kit. __________________ CD's Corner // Her first day // A year later // RX-8 Club 3Dmark06 - 4176 // 3Dmark05 - 7459 // 3Dmark03 - 14289 // PCmark05 - 4453 // PCmark04 - 6297

Jan 17, 2008, 09:32 PM	#8
CDsDontBurn 127.0.0.1 Join Date: May 2003 Location: Southern California Posts: 21,849 Rep Power: 133 System Specs	@ mike: sorry for the lack of details in my previous post. i was at work whe i made the post . now i'm at school posting from my smartphone __________________ CD's Corner // Her first day // A year later // RX-8 Club 3Dmark06 - 4176 // 3Dmark05 - 7459 // 3Dmark03 - 14289 // PCmark05 - 4453 // PCmark04 - 6297

Jan 17, 2008, 11:14 PM	#9
mike2h DriverHeaven Extreme Member Join Date: Nov 2002 Location: norcal Posts: 6,489 Rep Power: 74 System Specs	lol, no worries we are all just trying to help. you are doing a better job than i would under those circumstances. __________________

Sep 14, 2008, 12:29 PM	#15
cozumel I'm dangerous but cute... Join Date: Apr 2006 Location: Under the waves... Posts: 3,619 Rep Power: 42 System Specs	Hi hakujin and welcome to DriverHeaven. I think temeteus meant to say better getting 2x1GB and sell the 2x 512MB. The memory controller on your board will prefer this, plus it keeps everything dual channel which increases your transfer speed. As far as noticeable difference is concerned, why don't you set up your current 2x512MB modules so they no longer run in dual channel and do a direct performance comparison in the real world? __________________ Don't worry about money - Be a beach bum! Scuba Rocks Last edited by cozumel; Sep 14, 2008 at 12:39 PM.

Sep 14, 2008, 03:09 PM	#17
kris23 Going Insane..... Join Date: Dec 2006 Location: Los Angeles Posts: 5,312 Rep Power: 64 System Specs	the only way the above statement would work is in newer boards that support ASYMMETRIC DUal-Channel..... and that only works in P35 chipsets and newer as far as i know.... __________________ Driverheaven Super-Moderator Building a new computer system and not sure where to start? Click Here! last updated (9/4/09) New i5 systems with more to come! Building a PC: Step by Step Guide Written by Kristopher Pedemonte and Nathan Marks-Forder Edited by Allan Campbell Questions or Comments? feel free to post them in the forums!

Sep 14, 2008, 04:46 PM	#19
kris23 Going Insane..... Join Date: Dec 2006 Location: Los Angeles Posts: 5,312 Rep Power: 64 System Specs	9 series intel chips too? sounds right but theres definitely no assymetric dual channel in the old 8 series chips __________________ Driverheaven Super-Moderator Building a new computer system and not sure where to start? Click Here! last updated (9/4/09) New i5 systems with more to come! Building a PC: Step by Step Guide Written by Kristopher Pedemonte and Nathan Marks-Forder Edited by Allan Campbell Questions or Comments? feel free to post them in the forums!

Sep 15, 2008, 05:50 PM	#20
Matth Flash Banner Hater Join Date: Jun 2002 Location: UK Posts: 3,203 Rep Power: 57 System Specs	http://download.intel.com/design/chi...s/25273001.pdf Definitely, no asymmetric dual - use this link Intel® 875P Chipset Memory Configuration Guide White Paper if it refuses to go directly to the PDF. The 8 series offers single channel, "virtual single channel" (both channels loaded, not with a dual combination), dual channel (normal mode) and dual channel (dynamic mode). Dynamic mode is a bank switching performance optimization possible only when all modules are identically banked (same capacity, sides, page size). Dynamic mode will never be possible for two differently sized pairs, and depending on the architectures, might be possible for two same sized but non-identical pairs. It will be possible for matched pairs and quads, with a quad apparently giving the best performance under dynamic bank switching __________________ Mary had a little lamb, Her father shot it dead Now Mary takes her lamb to school, Between two crusts of bread

Sep 24, 2008, 09:46 PM	#21
hakujin DriverHeaven Newbie Join Date: Sep 2008 Posts: 3 Rep Power: 0	Pardon my delay. Thanks for all the info, it is appreciated, and noted. I decided to sell the Geil Ultra Dragon 3200; sold 2 512MB sticks for $22 on Craigslist, and purchased 2 1GB PC3200 Corsair Value Select sticks for $25 after rebate. Now I feel ike I have more than I know what to do with. Unlike my wife's Vista laptop which gobbled up the extra gig, it seems in MCE that I'm not fully utiizing it, but at least no more 90%+ RAM usage, and it's dual channel symmetric... who said DDR, HT, and Netburst is dead. Last edited by hakujin; Sep 24, 2008 at 11:05 PM.