Question Laptop 2400MHz RAM downclocking to 1333MHz?


Dec 28, 2009
I recently purchased a Dell Inspiron 7586 to replace a poorly functioning notebook. The Dell came with 1 stick of DDR4-2666 RAM, so I thought I'd move the dual channel 2400MHz I had in my old laptop. I thought the bus speed would drop 266Mhz, but I'd gain dual channel operation. Instead, when I look in HWINFO64 I see that my RAM's theoretical speed is 1200MHz, but the actual speed is 665 Mhz (1333MHz effective, I guess.)
Computer:      DELL Inspiron 7586
CPU:           Intel Core i7-8565U (Whiskey Lake-U, W0)
               2000 MHz (20.00x100.0) @ 4089 MHz (41.00x99.8)
Motherboard:   DELL 032K59
BIOS:          1.6.0, 07/19/2019
Chipset:       Intel Cannon Lake-U PCH-LP Premium
Memory:        16384 MBytes @ 665 MHz, 10-10-10-28
               - 8192 MB PC19200 DDR4 SDRAM - SK Hynix HMA81GS6AFR8N-UH
               - 8192 MB PC19200 DDR4 SDRAM - SK Hynix HMA81GS6AFR8N-UH
Graphics:      Intel UHD Graphics 620 (Whiskey Lake-U GT2) [DELL]
               Intel UHD Graphics 620, 1024 MB
Graphics:      NVIDIA GeForce MX150 (GP108) [DELL]
               NVIDIA GeForce MX150, 2048 MB GDDR5 SDRAM
Drive:         KBG20ZMS512G NVMe TOSHIBA 512GB, 500.1 GB, NVMe
Sound:         Intel Cannon Lake-LP - cAVS (Audio, Voice, Speech) [D0]
Network:       Intel Wireless-AC 9560
OS:            Microsoft Windows 10 Home (x64) Build 17763.973 (1809/RS5)
At first, I thought it might be because I was undervolting with Throttlestop, but the problem persisted after I disabled Throttlestop and rebooted. Anybody know why the laptop is underclocking the RAM modules?