Exact same RAM, with and without heatspreaders, works differently?

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XistenZ

XistenZ

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Jan 19, 2014
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I got a hold of an Dell Optiplex 780 (Small Form Factor), but without HDD and RAM. I tried with my RAM from my regular desktop just to see if it worked, which it did, so I ordered the same RAM but so called "low profile", or "LP" so that they can fit.
But the SFF-computer won't work with the LP-RAM, it gives me the beep-code 1-3-2 (RAM not detected). The LP-RAM works on my other desktop, so it's not that they're faulty. I tried swapping RAM again and put my originals in the SFF again, and it boots up fine.

CML8GX3M2A1600C9 - the Low Profile that only works on the desktop
CMZ8GX3M2A1600C9 - bigger heatspreaders, works on both computers

Specification-wise, these are identical. The only difference is the heatspreaders. How is this possible?

And to minimize unhelpful posts: yes, I inserted the RAM correctly. Yes, I checked for debris. Yes, I cleared CMOS. Yes, I removed the battery and made sure no power was left. Yes, everything has been done correctly. No, I will not use the non-LP on the SFF, because it doesn't fit when you add the HDD and reader. Yes, I want both computers to work, at the same time.
 
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neieus

neieus

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Looking at the provided specs for these two memory modules with the information provided by Corsair I can tell while they may have the same specs they are not exactly the same. The CML supports voltages of 1.5V and 1.35V only while CMZ supports 1.65, 1.5V and 1.35V. Since the CML doesn't work in the Dell that leads me to believe it's possibly a voltage problem. I've tried reviewing more detailed information about this computer but unable to find the boards voltage requirements just yet but right now it's the only thing that stands out.
 
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XistenZ

XistenZ

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Where did you find the information that says they support X voltage? I couldn't find it myself on Corsairs site.
And you're right in it's tricky to find information about the motherboard, and there's no S/N or model-nr on it either (hooray for computerbrands!). But, according to Crucial (http://www.crucial.com/usa/en/compatible-memory-for/Dell/optiplex-780-small-form-factor), their memories that's compatible with this "Dell Optiplex 780 SFF", is all 1.5v. Which would mean that even if a memory supports 1.65 (which was the only difference you could spot, right?), it doesn't matter since the board SHOULD only require 1.5v.

Ugh, I've never had problems with voltages like this. Things have always just worked unless they're bad/broken.
 
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neieus

neieus

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Correct that was the only difference I could find was the voltage. I was able to find it by using the model number you provided and searching through google http://www.corsair.com/en-us/vengeance-8gb-dual-channel-ddr3-memory-kit-cmz8gx3m2a1600c9 and http://www.corsair.com/en-us/vengeance-low-profile-8gb-dual-channel-ddr3-memory-kit-cml8gx3m2a1600c9. I also agree that it shouldn't matter since the board should only require 1.5v and I also checked the crucial website and noticed the same thing. The only additional thing I can think of is that from the beginning of this computer line to the end of it the system board could have had multiple revisions and multiple makers. Makes me wonder if say for example in the early revision the system board required 1.65v but by the end 1.5v however all that was speculation.

If I'm able to find any hard information I'll let you know.
 
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XistenZ

XistenZ

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I really appreciate your findings about the voltages anyway, I'm now installing Windows using the CMZ-modules, to see if I can grab the voltages using some sofware. Dell's BIOS wouldn't tell me, of course.

BTW, I looked at your link to Corsair, and that's the same I could find. The only thing that says anything about the different voltages is that they come in variations of 1.65, 1.5, and 1.35, not all at once. Or is it just that they can all use those voltages, but come preconfigured with a set voltage? As in all three variations is the exact same model, but clocked differently.
 
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XistenZ

XistenZ

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I found out the only software that can see memory voltage is CPU-Z (http://www.cpuid.com/softwares/cpu-z.html), and it says the memories run at 1.5v.
So it's still a mystery why modules without extra large heatspreaders won't work...
 
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