Dell Precision T5500 - adding 2nd cpu causes memory error

[imrazor]

When I attempt to add a riser card with a 2nd X5670 to my T5500, I get diagnostic lights 3 & 4 flashing when I try to boot. According to the manual this is a memory configuration error. Thing is, I have a pretty good selection of 2GB and 4GB ECC DDR3-1066 and DDR3-1333 DIMMs that work fine on the motherboard, but all get memory errors when used with the riser card. I've tried symmetrical configs (3x2GB on the motherboard and 3x2GB on the riser card, as well as 3x4GB on both boards.)

Anything else I can try to get this working?

 

[william p]

I wonder if it's looking for RDIMMs with a separate controller on each module for the 2 CPU setup to work.

 

[william p]

Also check to be sure that you have the 875W Dell PSU and the correct 2 CPU wiring harness 0R166H. The harness is a separate part, and the PSU was used in dual GPU Alienware and XPS gaming systems. You need the extra 8 PIN EPS (CPU) connector hooked up to the riser card.

 

[imrazor]

Also check to be sure that you have the 875W Dell PSU and the correct 2 CPU wiring harness 0R166H. The harness is a separate part, and the PSU was used in dual GPU Alienware and XPS gaming systems. You need the extra 8 PIN EPS (CPU) connector hooked up to the riser card.

No, the 8-pin connector coming from the power supply is plugged into the 2nd cpu riser card.

I'm truly stumped. All I can do is guess that the the motherboard's riser card connector is damaged somehow, preventing the memory from being accessed. I've tried two different riser cards and two different CPUs, and a whole slew of different DIMMs. All of the DIMMs work fine in the main board's DIMM slots, just not in either riser card.

 

[william p]

Did you try Registered DIMMS? The single CPU XEONs and single CPU workstations support the normal UDIMM memory. But the 2 CPU XEONs and 2 CPU workstations all support RDIMM (Registered) RAM. The 2 CPU XEON CPUs can run UDIMMs in single CPU applications. It may be that the riser only supports RDIMM memory since that's what a system configured with 2 CPUs would have had.

 

[imrazor]

I'm about 90% sure they're RDIMMs. I'll double check once I get back home. Any other suggestions?

 

[william p]

2xCPU and RDIMMs should work. Nothing other than that.