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October 13th, 2025 13:37
What speed will 64 gig 2933 lrdimms operate in an r740?
I have an r740 with a pair of second gen Xeon scalable CPUs - M sku. I am looking at getting 8-12 dimms and the documentation seems to indicate that while 64 gig 2933 rdimm modules will run at 2933, lrdimm modules seem limited to 2666. Has anyone tested this and can confirm? 2933 rdimms are a bit more expensive than 2933 lrdimms so I’d just as soon go lrdimm, but if the speed is limited then I can save more by getting the 2666 sticks. The documentation doesn’t specifically note 64 gig 4r lrdimms on second gen however, just 8r 128 gig
Thanks for any info!
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Xavier Martinez
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October 13th, 2025 16:57
On the r7920 ( should be the same MB as the r740), you get full speed if :
- The CPU supports it 62xx, 82xx
- 1Dimm per channel (1DPC). you have (6 channels per CPU, 2 dimm slots per channel)
If you install 2DPC, then it clocks down to 2666MT/s.
Having "M" Xeon's only let's you increase the total amount of RAM.
https://www.delltechnologies.com/asset/en-us/products/workstations/technical-support/dell-precision-7920-rack-technical-guidebook.pdf
user_05615a
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October 13th, 2025 17:42
That makes sense - so up to 12 dimms (6 per cpu) 2933 lrdimms should function at the expected 2933 speed with an 82xx Xeon instead of dropping to 2666. This is despite the doc noting 2933 speeds for rdimm specifically- lrdimms should be the same as far as the system is concerned, provided the other factors are met correctly?
Sounds good, thank you!
(edited)