funkkube,
Click the link below and download the Dell Precision™ T5500 Service Manual. The memory configurations will be listed in the service manual.
Dell Precision T5500 Drivers, Downloads and Manuals

You cant mix density and rank and speed and vendor and ecc vs non ecc.

No such specification as 888 or 222.

https://downloads.dell.com/manuals/common/precision-t5500_setup%20guide_en-us.pdf

Specs: DDR3 PC3-12800 • CL=11 • Dual Ranked • x8 based • Registered • ECC • DDR3-1600 • 1.35V • 1024Meg x 72 •

 Slots:6 (2 banks of 3)

Single Dual and Quad Rank ram cannot be mixed.

Quad Rank Ram is NOT SUPPORTED

HIGH Density Ram is NOT Supported.

speedstep,

You said there is "No such specification as 888 or 222."

I think he may have a riser card with the slots filled with 8,8,8,2,2,2,2,2,2 GB sticks in the first machine. This would indeed add up to his specified 36GB RAM. (At least that's how I read his post)

I would suggest moving the RAM from Machine #1 into the corresponding slots in Machine #2 to see how it goes. Speedstep is indeed correct that you can't mix different types of RAM, so please verify what sort of sticks are installed in each T5500. The OP may have Unbuffered ECC installed in one machine and Registered ECC in the other.

Randy

I have dell T5500 workstation the problem is DIMM 2 is not working but DIMM1 and DIMM3 is perfectly working I need 16GB RAM can I use 8GB + 8GB in DIMM1 and DIMM3 please reply me

I had a similar problem, after cleaning the T5500 for dust.  Tiny fragments of dustbunnies got into the DIMM slots causing DIMM slot errors.  Used an electronics solvent to wash them out, now working fine.

Does the dell t5500 support a 16 gig memory ram configuration 

@Eliahenley

Thank you for reaching out to us. Precision T5500 system model supports 1GB - 8GB DIMM sizes. Maximum Memory: Single CPU: 48GB and Dual CPU: 72GB.

Here is the link https://dell.to/2SnCksl which has more information. 

@speedstep​ |

Thank you sir.