Memory appears to be running really slow

[imrazor]

I recently purchased a 'new' laptop, an open box Dell Inspiron 7586. It came with a single stick of DDR4-2666 RAM, so I decided to pull the dual channel set from my old, semi-functional laptop and put it in the new notebook. The old laptop had a pair of 8GB DDR4-2400 RAM, so I thought the memory controller would just downclock to 2400/1200 MHz, but I'd still get a much higher effective speed with a dual channel set up. That doesn't appear to have happened.

Instead the memory is showing up as a speed of 665MHz, or about 1333MHz when double data rate is accounted for. Can this possibly be right? See attached log.

Memory --------------------------------------------------------------------

[General information]
  Total Memory Size:                      16 GBytes
  Total Memory Size [MB]:                 16384
[Current Performance Settings]
  Maximum Supported Memory Clock:         1200.0 MHz
  Current Memory Clock:                   665.2 MHz
  Current Timing (tCAS-tRCD-tRP-tRAS):    10-10-10-28
  Memory Channels Supported:              2
  Memory Channels Active:                 2
  Command Rate:                           1T
  Read to Read Delay (tRD_RD) Same Rank:  4T
  Read to Read Delay (tRD_RD) Different Rank: 4T
  Read to Read Delay (tRD_RD) Different DIMM: 7T
  Write to Write Delay (tWR_WR) Same Rank: 4T
  Write to Write Delay (tWR_WR) Different Rank: 4T
  Write to Write Delay (tWR_WR) Different DIMM: 7T
  Read to Write Delay (tRD_WR) Same Rank: 8T
  Read to Write Delay (tRD_WR) Different Rank: 8T
  Read to Write Delay (tRD_WR) Different DIMM: 10T
  Write to Read Delay (tWR_RD) Same Rank (tWTR): 19T
  Write to Read Delay (tWR_RD) Different Rank: 16T
  Write to Read Delay (tWR_RD) Different DIMM: 6T
  RAS# to RAS# Delay (tRRD):              4T
  Refresh Cycle Time (tRFC):              234T
  Four Activate Window (tFAW):            16T

 

[Martin]

That information should be correct, you might double-check with some other tool like CPU-Z.

 

[imrazor]

Instead of looking at the static configuration tree, I took a look at the real time data. I found that the memory speed is constantly switching between 666mhz and 1200mhz. It might be a power saving measure, but even when the system is under full load (video export, etc.) the speed is constantly fluctuating. I really don’t know what to make of it.

 

[Martin]

Oh yes, memory controllers in latest CPUs feature such power management modes and can dynamically switch memory clock/timings, it's normal.