Why can I not run my memory in dual channel?

[SeanM]

System specifications:

Motherboard: ASUS P4P800 SE
Processor: P4 3.0 E E0 S478 @ 3.6 GHZ (240 FSB * 15)
Cooling: Zalman CNPS7000B-AlCu P4 Cooler
Memory: 2 X Crucial 512 MB PC3200 DDR 2.5 3 3 6 (5:4 setting)
Graphics: Sapphire 9800 Pro 128 MB
Sound: Sound Blaster Audigy 2
Power: Antec True Power 480 Watt PS


Why can I not run my memory in dual channel?

I have had 2 identical P4P800 SE rigs running a Celeron D and a P4 3.0E. I have never been able to get my memory running in dual channel mode. When I search this forum I don’t see many people having this issue. My sticks are in the proper slots for dual channel (1 and 3). The MB support dual channel. What am I missing here?

When I check CPUZ and look and the SPD of each stick of memory there are differences in the descriptions of the sticks but the SPD timings are the same. I have tried everything I can think of the get these working, you advice is much appreciated.

-Sean

[kimochii72]

I had this very wierd issue myself with my new opteron. After installing systool, I ran each stick separately, just one at a time and tested its max overclock. Did a stability test on each near it's max overclock. Then I added each one and did the same thing, then added the 3rd, did max overclock on the ram again, ran stablity test, next thing I knew, by the 4 stick was in everything was finally running 128bit instead of 64bit single channel. My computer now kicks-butt.

[batboy]

You have two identical P4P800 systems and neither will run in dual channel? What RAM is/was in the other system? The sticks should be matched, meaning same brand, speed, and capacity. They should be installed in either slots 1&3 or 2&4 (slots that are the same color). I had an Abit mobo once that was working in dual channel, then went to single channel after I was trying some high end overclocking. I finally got it working in dual channel again by clearing the CMOS. Might also try updating the BIOS. If all that fails, then maybe those two RAM modules just plain don't play well together or maybe one is defective. Might try running Memtest on them individually and together. Do you or a buddy have another pair of RAM that could be tried? How are you determining that dual channel is not working?

[SeanM]

Hi batboy,

Thanks for your reply, let me try to address your questions:

The exact same 2 sticks of RAM will not run dual channel in my P4 system and in my old (decommisioned ) celeron system. Because I have attempted this on 2 P4P800 motherborads I assume the MB is not at fault.

the memory is 2 X Crucial 512 MB PC3200 DDR installed in slots 1 and 3. They are not matched pairs but were purchased at the same time and have the same SPD timings in CPUZ. The vendor information is different though. One stick is labled micron the other is generic. Does the MB determin if 2 sticks can run in dual channel by reading this vendor information in the SPD?

I know the memory is not in dual channel because CPUZ states the mode is single channel.

The memory has been MEM tested separately and checks out. They are actually 2 really solid sticks of memory and run at tight setting or a high overclock. They just don't run in duial channel.

Perhaps I need to bite the bullit and get a "guaranteed matched pair". How much performance am I loosing by running in sigle mode?

-Sean

[batboy]

You are losing nearly half your potential memory bandwidth. Run the Sandra memory bandwidth benchmark and see what you're getting. Double that and you have what it would of been if you were running dual channel.

The motherboard does read the SPD. Most times you can get two sticks to run if they are close to the same. In other words a perfect match is recommended, but is not always required. I think you have the bad luck of two sticks that don't like to play well together in dual channel. Since you have tried the same two sticks in two motherboards, that appears to be the case. They would probably work perfectly fine in a socket A AMD system.

Have you tried clearing the BIOS yet? Do you have an updated BIOS? Have you tried running a different pair of RAM in the mobo? Have you tried using slots 2 & 4? What score do you get in Sandra memory bandwidth benchmark?

[FlailBoy]

...The vendor information is different though. One stick is labled micron the other is generic.

FYI-Probably Samsung.

[SeanM]

I benchmarked my memory and got some confusing results:

I am wondering if the memory in each chip is organized differently. The reason I think this is that the computer seems to see 3 banks of memory 1 of 512 and 2 of 256. Can anyone comment on these test results. Do I have 2 different and incompatible sticks of memory?


SiSoftware Sandra

Benchmark Results
RAM Bandwidth Int Buff'd iSSE2 : 2843 MB/s
RAM Bandwidth Float Buff'd iSSE2 : 2842 MB/s
Results Interpretation : Higher index values are better.

Int Buff'd iSSE2 (Integer STREAM) Results Breakdown
Assignment : 2843MB/s
Scaling : 2845MB/s
Addition : 2843MB/s
Triad : 2841MB/s
Data Item Size : 16 byte(s)
Buffering Used : Yes
Offset Displacement Used : Yes
Bandwidth Efficiency : 89% (estimated)

Float Buff'd iSSE2 (Float STREAM) Results Breakdown
Assignment : 2843MB/s
Scaling : 2845MB/s
Addition : 2843MB/s
Triad : 2838MB/s
Data Item Size : 16 byte(s)
Buffering Used : Yes
Offset Displacement Used : Yes
Bandwidth Efficiency : 89% (estimated)

Performance Test Status
Run ID : SPARTACUS on November 29, 2005 at 10:26:51 PM
Memory Used by Test : 512MB
NUMA Support : No
SMP Test : No
Total Test Threads : 1
Multi-Core Test : No
SMT Test : Yes
Dynamic MP/MT Load Balance : No
Processor Affinity : P0C0T0
Page Size : 4kB
Use Large Memory Pages : No

Chipset 1
Model : ASUSTeK Computer Inc 82865G/PE/P, 82848P DRAM Controller / Host-Hub Interface
Front Side Bus Speed : 4x 240MHz (960MHz data rate)
Width : 64-bit
Maximum Bus Bandwidth : 7680MB/s (estimated)

Logical/Chipset 1 Memory Banks
Bank 0 : 512MB DDR-SDRAM 2.5-3-3-6 1CMD
Bank 4 : 256MB DDR-SDRAM 2.5-3-3-6 1CMD
Bank 5 : 256MB DDR-SDRAM 2.5-3-3-6 1CMD
Channels : 1Speed : 2x 200MHz (400MHz data rate)
Width : 64-bit
Performance Acceleration Technology : No
Maximum Memory Bus Bandwidth : 3200MB/s (estimated)

Features
(W)MMX Technology : Yes
SSE Technology : Yes
SSE2 Technology : Yes
HTT - Hyper-Threading Technology : Yes

Performance Tips
Notice 5406 : System bandwidth appears memory limited. Attempt to use higher-performance memory.Notice 5008 : To change benchmarks, click Options.
Notice 5004 : Synthetic benchmark. May not tally with 'real-life' performance.
Notice 5006 : Only compare the results with ones obtained using the same version!

[SeanM]

I ran some additional diagnostics and got the following information. What does this mean?

SiSoftware Sandra

Number of Memory Slots : 4
Maximum Installable Memory : 4GB
BANK0 - DIMM0 : Manufacturer0 PartNum0 SerNum0 AssetTagNum0 DIMM Synchronous DDR-SDRAM 512MB/64
BANK1 - DIMM1 : Empty
BANK2 - DIMM2 : Manufacturer2 PartNum2 SerNum2 AssetTagNum2 DIMM Synchronous DDR-SDRAM 512MB/64
BANK3 - DIMM3 : Empty

Logical/Chipset 1 Memory Banks
Bank 0 : 512MB DDR-SDRAM 2.5-3-3-6 1CMD
Bank 4 : 256MB DDR-SDRAM 2.5-3-3-6 1CMD
Bank 5 : 256MB DDR-SDRAM 2.5-3-3-6 1CMD
Channels : 1
Speed : 2x 200MHz (400MHz data rate)
Multiplier : 5/6x
Width : 64-bit
Refresh Rate : 7.80µs
Performance Acceleration Technology : No
Power Save Mode : No
Fixed Hole Present : No

Memory Module 1
Manufacturer : Micron
Model : 8VDDT6464AG-40BDB
Serial Number : 23187262
Type : 512MB DDR-SDRAM
Technology : 8x(64Mx8)
Speed : PC3200U 3.0-3-3-8
Version : 1.1
Date of Manufacture : August 12, 2004
Set Timing @ 200MHz : 3.0-3-3-8
Set Timing @ 167MHz : 2.5-3-3-7
Set Timing @ 133MHz : 2.0-2-2-5

Memory Module 2
Type : 512MB DDR-SDRAM
Technology : 16x(32Mx8)
Speed : PC3200U 3.0-3-3-8
Version : 1.1
Date of Manufacture : January 6, 2005
Set Timing @ 200MHz : 3.0-3-3-8
Set Timing @ 167MHz : 2.5-3-3-7
Set Timing @ 133MHz : 2.0-2-2-5

[batboy]

Well... you are definitely only running single channel with that bandwidth score. Frankly, I don't know what to make of the "Logical/Chipset 1 Memory Banks" showing 512, 256, and 256. Doesn't look like the memory plays well together.

[MisterEd]

Is "8x(64Mx8)" single-sided RAM and "16x(32Mx8) double-sided RAM?

If that is true then would that be the problem since you would be mixing RAM types?

[SeanM]

Would double sided ram have chips mounted on both sides of the stick? I can't belive I did not notice that. (and that the store sold the pair to me like that). I will take a look when I get home tonight. Looks like I need a match pair of new memory.

-Sean