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jluschen



Joined: 19 May 2020
Posts: 5
Location: San Diego
jluschen
Gentlemen-

I've come here with my question because this board seems to be bursting with bona fide computer brainiacs.

I have two Dell Optiplex 9010 computers that are virtually identical. But one behaves badly, and I cannot figure out why, or how to fix it. I run Windows on both. They have the same revision of BIOS. The problem is the memory sticks. One computer works great, the other will not use more than two sticks of memory (up to four can be installed on this motherboard).

If 4 sticks are installed, the computer boots and runs with only 2 sticks active -- BIOS reports two of the four slots as empty even though they are filled. At first I thought the slots were damaged (I knew the sticks were all good, from swapping them around and from using them in the other computer). First I tried using 4 sticks of 4GB, then I tried using 4 sticks of 8GB. Both times I saw just half the actual memory.

Now for the STRANGE part. If I mix the sticks together and use two 4GB sticks and two 8GB sticks, BIOS will find and use the two 8GB sticks and report the other slots as empty. It makes no difference which slots get the 8GB sticks, BIOS finds them and runs with only them. If I use one 8GB stick and three 4GB sticks, BIOS finds the 8GB stick and then reports 12GB total, with two of the slots reported as empty. So it appears BIOS figures out how to get the most total memory using just two slots, and then proceeds to do just that.

So to summarize the problem:

1- My computer uses 1 or 2 sticks of memory just as it's supposed to; it doesn't matter which particular slots are populated, both are seen and used.

2- If more than 2 sticks are inserted, it will find and use only the two highest capacity sticks. Slot selection never affects this behavior.

3- BIOS shows the two "found" slots as correctly filled and the other two slots as empty (even though they aren't empty).

4- Windows boots but uses only those 2 sticks of memory. This could be 8GB, 12GB, or 16GB, depending on how I shuffle the eight sticks and deal them out to the slots.

5- Lastly, HWiNFO64 (a diagnostic program running under Windows) always sees all 4 (or fewer) sticks and reports them correctly, including S/N and date code.

I've since learned that the memory stick's manufacturing information and timing parameters are stored in on-board EEPROM that can be read using an I2C bus. I suppose the HWiNFO64 diagnostic tool must get the information it reports without asking BIOS what is there, and without actually exercising the memory bus. This I2C circuitry is alive for all four slots since the tool always sees 4 sticks correctly.

Does this make sense to anyone? What is BIOS doing? How might I fix it?

jluschen
Post 19 May 2020, 20:32
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17270
Location: In your JS exploiting you and your system
revolution
Your motherboard could be faulty. Send it back for a replacement.
Post 19 May 2020, 22:55
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jluschen



Joined: 19 May 2020
Posts: 5
Location: San Diego
jluschen
Mr. revolution, thank you for your suggestion.

I cannot rule out a faulty motherboard, but I also cannot envision a fault that does what this board does. Do you have a suggested mechanism for the observed behavior?

All I can think of is a weak power supply that cannot keep 4 sticks running, so BIOS decides to do the best that it can. But would BIOS be designed to overcome such a rare motherboard fault? In fact, would BIOS be designed to overcome ANY motherboard fault? And how and why would BIOS be able to find the big sticks, and then use them only?

Remember that every memory stick slot on the board works fine by itself, and also when one other slot is populated.

As for returning it, the warranty is expired. It was purchased second-hand anyway, so Dell cannot help me. Dell's discussion board also could not help me. I came here because I sensed some BIOS-knowledge in other posts, and a higher level of computer expertise in general. This board is not a collection of your basic Joe Blows (your crazy-difficult "what's the biggest number using nine ascii characters?" challenge is evidence enough of that, I never heard of half that stuff before).

If I could, I have a second request: do you know any other web sites where this inquiry might find traction? (What I'd really like is a commented copy of the source code for my BIOS).

Thanks again-
jluschen
Post 19 May 2020, 23:24
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17270
Location: In your JS exploiting you and your system
revolution
There are many faults that can be caused by the mobo, or the components on it. The memory interface is very complex. Trying to determine precisely which part could cause such behaviour would be very difficult, especially since the internal details are not published.

It is not the job of the BIOS to correct any faults. Things are supposed to be working.

Please don't assume I am Mr.
Post 19 May 2020, 23:38
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jluschen



Joined: 19 May 2020
Posts: 5
Location: San Diego
jluschen
I'm sure you are right that the circuits are very complex.

I wonder what your opinion of this is:
https://vinafix.com/threads/dell-lainikai-mt-dt-dell-optiplex-7010.19197/

This page makes available a schematic for a Dell 7010 motherboard, which may be the same as mine. I need to pay for a registered account before I can download the file. A one-day registration is not much, just $3. Do you think it is authentic?
Post 19 May 2020, 23:55
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17270
Location: In your JS exploiting you and your system
revolution
The mobo schematics won't show the IC internals. If, say, the Northbridge controller has a weak transistor causing memory issues then you would have a very troubling time trying to debug that. And obtaining a replacement IC might also be a big ask. And physically replacing it needs some expensive kit if you want to not damage other parts of the board.

I personally don't see any way forward to diagnosing things short of getting a replacement and see if it fixes it.
Post 20 May 2020, 00:06
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bitRAKE



Joined: 21 Jul 2003
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bitRAKE
There are lots of different types of memory stick configurations. I don't think it'd be beyond DELL to support only a very specific configuration. Even finding DDR3 1600Mhz on a search doesn't tell the whole story. Mixing ram types can force the motherboard to choose even if it supports both types - as it doesn't need to support both types concurrently.

If all memory modules are the same type then it's most certainly a hardware failure.

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Post 20 May 2020, 00:43
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jluschen



Joined: 19 May 2020
Posts: 5
Location: San Diego
jluschen
Yes, even if all the memory is the same (i.e. 4 identical 4GB sticks) the machine only "sees" two of them. But you can mix two sticks of different memory voltage and size without a problem.

It just never acknowledges more than two sticks.

One other note: The seller listed it as 16GB (four 4GB sticks). When I checked memory before paying him we saw Windows reported only 8GB. This surprised him, but he adjusted his price downward so I paid him and left. At home I opened it to add memory and found four 4GB sticks were in there, and the boot log file said that sometime in the recent past the amount of memory had been changed. I guess that would seem to point to a hardware failure, since I don't believe the BIOS was updated -- it was still the version that shipped from Dell. I have since updated the BIOS but that didn't help.

But what kind of hardware failure has these symptoms?
Post 20 May 2020, 01:31
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sleepsleep



Joined: 05 Oct 2006
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sleepsleep
how about swapping the bad Dell Optiplex 9010 motherboard into the good Dell Optiplex 9010?
then you have exact condition to test if the issue caused by power supply

i noticed you mentioned both bios are same version, but are they under same configuration?

maybe a default reset on both is another step to test,


Last edited by sleepsleep on 20 May 2020, 01:42; edited 1 time in total
Post 20 May 2020, 01:39
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bitRAKE



Joined: 21 Jul 2003
Posts: 2913
Location: [RSP+8*5]
bitRAKE
I'd check the obvious stuff like bloated caps, or using your sniffer to detect anomalous smells (not likely if it's been stored a long time). Don't really expect such things in something 6-7 years old. Could be anything from a resister knocked off the board or a scratch across some traces.

It might be better to just run with two sticks and call it a day, or get your money back.

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Post 20 May 2020, 01:40
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jluschen



Joined: 19 May 2020
Posts: 5
Location: San Diego
jluschen
Thank you sleepsleep, thank you bitRAKE, I can try more swapping between computers when I finish my current project (can't live without this computer right now).
Post 20 May 2020, 01:59
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