Dell/Alienware - Precision Workstation T5500

Kingston offers "K3" kit part numbers for Triple Channel mode.
DDR3 1333MHz speed requires Intel Xeon X5550 or higher processors. 1066MHz requires Xeon E5520 or higher, Xeon E5506 or lower support 800MHz only. Memory speed will be reduced as the number of modules installed increases. 1333MHz is supported with one DIMM per channel only using Xeon X55xx series.
Faster memory will clock down to run at optimal speed and voltage depending on processor model and number of modules installed
This system supports either Registered ECC or Unbuffered ECC memory. Mixing Registered ECC and Unbuffered ECC modules is NOT supported within this system.
Due to chipset limitations, Unbuffered ECC DIMMs are limited to TWO Triple Channel banks per processor on Intel Xeon 55xx series systems.
Per Dell documentation, DIMMs within a memory channel need to be populated starting with the DIMM sockets farther from the processor first. DIMM slots 1, 2 and 3 must be populated before DIMM slots 4, 5 and 6. When installing quad-rank DIMMs with a single or dual-rank DIMM in the same channel, the quad-rank DIMMs must be populated farthest from the processor.
To maximize available memory bandwidth, DIMMs should generally be spread across as many channels as possible before populating multiple DIMMs per channel.
Single-CPU memory configurations (6 DIMM slots on MB):

1. For configurations containing DIMMs of all the same capacity, populate in the following order:
DIMM1, DIMM2, DIMM3 then DIMM4, DIMM5 and DIMM6
2. For configurations containing DIMMs of mixed capacities, populate the larger DIMMs first.
Dual-CPU memory configurations (6 DIMM slots on MB plus 3 DIMM slots on Riser Card):
1. For configurations containing DIMMs of all the same capacity, populate in the following order:
MB_DIMM1, Riser_DIMM1, MB_DIMM2, Riser_DIMM2, MB_DIMM3, Riser_DIMM3, MB_DIMM4, MB_DIMM5 & MB_DIMM6.
2. For configurations containing DIMMs of mixed capacities, populate the larger DIMMs on the Riser card.
4GB DDR3-1333 Reg ECC modules come in two versions: 313/4G using x4 and 3138/4G using x8 DRAM. The two parts may be installed in the same system but not within the same memory bank. Use like modules for dual and triple channel operation.