Precision 5820: 3200MHz Memory Started Running at 2666MHz After BIOS Update

Question

My Precision 5820 has 4x32GB Crucial 36ASF4G72PZ-3G2R1 3200MHz DIMMs - all purchased directly from Crucial/Micron and guaranteed to work with this model. These were running at 3200MHz, but after a recent BIOS upgrade the BIOS reports the system running at 2666MHz. Worse, even after downgrading the BIOS back to the prior version it still runs only at 2666MHz. I don't see anywhere in the BIOS to configure this, or to get a reason why the speed downgrade happened. I've checked the memory specs with dmidecode and all 4 DIMMs correctly report the speed as 3200, but "configured memory speed" as 2666. I've copied one of the reports below. The DIMMs are in the 1-4 positions, so it shouldn't be related to install order.

Does anyone have any ideas? Appreciate any and all help.

Array Handle: 0x0009
Error Information Handle: Not Provided
Total Data Size: 32 GB
Form Factor: DIMM
Set: None
Locator: DIMM3
Bank Locator: Not Specified
Type: DDR4
Type Detail: Synchronous
Speed: 3200 MT/s
Manufacturer: Micron
Part Number: 36ASF4G72PZ-3G2R1
Rank: 2
Configured Memory Speed: 2666 MT/s
Minimum Voltage: 1.2 V
Maximum Voltage: 1.2 V
Configured Voltage: 1.2 V
Memory Technology: DRAM
Memory Operating Mode Capability: Volatile memory
Firmware Version: NA
Module Manufacturer ID: Bank 1, Hex 0x2C
Module Product ID: Unknown
Memory Subsystem Controller Manufacturer ID: Unknown
Memory Subsystem Controller Product ID: Unknown
Non-Volatile Size: None
Volatile Size: 32 GB
Cache Size: None
Logical Size: None

ejn63 · Answer

What CPU does the system have (Intel W-2223, W-2133, etc.)?

mazzinia_ · Answer

After the bios downgrade , try doing a bios reset to factory settings (save down your settings first)

WhatDellsCrave · Answer

@ejn63​ Processor is Intel W-2195

Chino de Oro · Answer

With a Xeon Skylake processor, memory will operate at 2666 MHz. See memory specifications for more details. https://www.dell.com/support/manuals/en-us/oth-xlt5820/precision_5820_om_pub/memory-specifications?guid=guid-5ee14007-db24-4d37-aecb-34dea3370abb&lang=en-us

WhatDellsCrave · Answer

@Chino de Oro​ Thanks for the link. I saw that official support note, but the odd thing is that it was running at 3200 successfully before the BIOS update.

WhatDellsCrave · Answer

@mazzinia_​ Good idea. Tried it, but unfortunately it is still running at 2666 even after a factory setting reset.

ejn63 · Answer

This CPU is not capable of running RAM at 3200 MHz -- as noted.

WhatDellsCrave · Answer

@ejn63​ I get that it's not officially supported, but it did run at 3200 earlier.

ejn63 · Answer

It actually wasn't, since that's impossible. It's very possible an older BIOS/firmware mis-identified the RAM speed, and the detection of speed was corrected in the newer version, but no -- the RAM was not running at 3200 MHz before. It cannot with this CPU. If you were using a utility to see the memory speed, it's equally possible whatever utility that was mis-identified the speed of the memory.

The CPU controls the memory speed -- and the one you have cannot run RAM at 3200 MHz.

WhatDellsCrave · Answer

@ejn63​ Appreciate your attempt at help.

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Precision 5820: 3200MHz Memory Started Running at 2666MHz After BIOS Update

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