Not exactly sure what you have tried, but if you have two memory DIMM's, they must be in slots 1A and 1B:

Review the documentation for specifics:

<ADMIN NOTE: Broken link has been removed from this post by Dell>

<ADMIN NOTE: Broken link has been removed from this post by Dell>

Thank you theflash1932!

I have four x 2GB RAM DIMM's all are same model and all work fine.

If I use only DIMM_1A and DIMM_1B I've no problem, if I use DIMM_2A and DIMM_2B also, T100 doesn't boot and start with several beeps. I tried to invert RAM DIMM's but only configuration in DIMM_1A and DIMM_1B works!

If all the DIMM's work when in slots 1A and 1B, then I'd say you have an issue with either slot 2A or 2B.  Try clearing the NVRAM using the jumpers on the motherboard.  If that doesn't work, then you are likely looking at replacing the board to address the slot issue.

Did the memory come from Dell?  What is the exact model number/specs of the memory?

I have the same exact problem.  Did you find a solution?

So there is no confusion I tried using 4 crucial identical memory sticks and it beeped.  When I use just two it works fine. I tried to use two crucial and two kingston and it beeped but when i used two kingston it worked fine.

What have you tried?  Have you tried any of the steps laid out in this thread?

Yes I have. It seems that I can only get 2X2GB to work.  I tried using different brands and it has the same result.  It works with two kingston 2gb pc2 6400 or 2 crucial 2gb pc2 6400 but will not work with four with any combination of memory sticks.

You've tried clearing the NVRAM?  Have you updated BIOS?  What version are you running?

Describe your problem in detail ... problems aren't often exactly the same.  System model?  RAM module size, speed, layout, model number, etc.

Any answer to this?  I am having the exact same problem.  Thanks!

I am actually having the exact same problem.  This is on a Poweredge T100.  It came from the factory with 4GB Ram (2 x  2GB DDR2 - 800).  We are attempting to add 4GB more additional to get it to its max of 8GB Ram.  So we purchased 2 more 2GB DDR2 - 800 sticks.  We attempted to install the sticks on Friday putting them in Dimm2A and Dimm2B and upon restarting up the box we would get the 1-3-2 beep, no memory installed.  We can remove the two additional sticks and it boots up just fine.  We took out the original RAM from Dimm1a and 1b, and swapped in the new sticks of RAM to see what would happen.  Worked just fine with 2 new sticks of RAM in Dimm1a and 1b.  So its definitely not the sticks.  

We are running 1.3.4 for the BIOS, 1 below the current 1.4.1, but I just looked up to see if there was anything addressing this issue in the new BIOS release and there was not, so I am not seeing any reason for having to upgrade to 1.4.1.

Am I missing some configuration issue here?  It seems funny others are running into an issue like this.  Any help would be appreciated.

Thanks

The specs for the T100 memory are pretty basic ...

• 2GB max per slot, 8GB total
• 667 or 800 MHz
• must be unbuffered (UDIMM), not registered (RDIMM)
• must be ECC
• may be single rank or dual rank (may be limitations when mixed)

One thing that stands out to me is this:

NOTICE: If you remove your original memory modules from the system during a
memory upgrade, keep them separate from any new memory modules that you may
have, even if you purchased the new memory modules from Dell. Use only
unbuffered ECC DDR II memory modules.

This suggests that the ORIGINAL memory may somehow be different from standard memory.  How do the labels compare, as far as their descriptions ... do the layouts/geometry/specs match?

The RAM we have is 2GB, 800 mhz, UDIMM, ECC DDR2.  Matches up spec for spec to the OEM memory.  I actually gave the part number of the original DELL RAM to the memory vendor, and he looked it up and grabbed these two sticks for me for it.  The memory modules themselves look very similar from my new ones to the OEM ones.  I can swap them in to Dimm 1a and 1b no problems.  

After thinking more about your ranking and admittedly I was not sure on this I did a little research and I am not seeing anything relating to this server, but on another page about the ranks I am seeing this maybe the issue: en.community.dell.com/.../17447271.aspx

"The system supports both single-ranked and dual-ranked memory modules.

If you install both single-ranked and dual-ranked memory modules, the dual-ranked memory modules must be installed in bank 1.

Dual-ranked memory modules are not supported in bank 3.

If dual-ranked memory modules are installed in bank 2, you cannot install memory modules in bank 3."

I am wondering if that is what we might be running into here...Hmmm.