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21145
May 8th, 2009 21:00
DDR2-800 memory incompatibility ?
I just bought a Dell T3400 Workstation. It has 4 DIMMs slots. It was ordered with 2x 1 GB DDR2-800 memory. DIMMS are installed in the right slots to provide dual channel operation. No problem until here. I bought 2x 1GB DDR2-800 Kingston memory. I add DIMMs to the system. Problems start here. The memory frequency drop to 667 MHz. I remove the memory shipped with the PC (Promos brand) and let installed the Kingston memory. The memory frequency resume to 800 MHz. So I guess there is a memory incompatibility between module but cannot find what it is and why it doesn't run to 800 MHz when the 4 DIMMs are installed..
Here is the memory specification.
Promos memory : DDR2-800, 1.8V, CL6-6-6, 8 IC on each side of the module, unbuffered, non-ecc
Kingston memory : DDR2-800, 1.8V, CL5-5-5, 8 IC on 1 side of the module, unbuffered, non-ecc
Do I have other memory spec that I must look for?
Davet50
4 Operator
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14.4K Posts
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May 9th, 2009 06:00
Your bios cannot handle the different timing specs of the modules. Since you have no tweaking ability this will confuse the bios as to what timings to run therefore the bios will drop the memory controller to the slower 667 speed to run the memory.This is a protection setting of the memory controller.
Since you have CPU-z installed you need to go to the SPD tab with the memory and look at the different SPD settings that are programed into each stick.
It only takes a slight difference in memory SPD's to cause the memory to not run at full specs when all four slots are populated. And There can be a difference between the same memory brands with just a few months difference in manufactor dates.
Therefore you need to get all the exact same memory to run the system at 800mhz.
NEX_SASIN
2 Posts
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May 8th, 2009 22:00
Yes as you can see the CL-6-6-6 and Kingston is 5-5-5.. thier latency timing is different therefore need to drop to the same rate in order for them to work together. And mind you, the lower latency timing = better performance. Obviously Kingston is the winner here. The promo memory must be Samsung.
PH3N0M
650 Posts
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May 8th, 2009 23:00
No, it's not a compatibility issue. The DDR2-800 memory can only run at 800mhz if the other modules are also rated at 800mhz. If you install DDR2-667 modules next to the 800, they will slow down to match the DDR2-667 speed. If you want to run 4gb of ram, you need to purchase another 2x1gb of DDR2-800 memory.
dcomeau25
3 Posts
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May 9th, 2009 06:00
When all 4 DIMMs are installed, my system shows 4 GB of ram. As I can see in CPUz, the SPD tab shows a 400 MHz frequency in timing table for each of 4 modules. So all my memory is DDR2-800 (I know that CPUz shows the real clock). The only difference is the timings.
Furthermore, when I only installed the promos memory, it runs to 800 MHz and when I only installed the Kingston memory, it runs to 800 MHz. The problem is when I installed 2x promos + 2x Kingston.
I was expecting to get a memory frequency of 800 and use the timings of the slowest module, in this case CL6-6-6. Instead, I get a memory frequency of 667 with memory timings of CL5-5-5. Do anyone know why the system choose this setup?
dcomeau25
3 Posts
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May 9th, 2009 09:00
Thank you for the explanation. I'll try to change my memory and get same spec for all 4.