Its me again, after awhile i decide to upgrade 16GB Kingston DDR4 2400 which is currently world fastest notebook DDR4. Do you guys think worth it compare to stock RAM with 2133? what can i expect after the upgrade? targeting to swap out stock 16GB 2133 and replace with 16GB kingston hyperx impact 2400. Worth it or no?
Frequency is more important than latency, DDR4 manufacturers have always bumped raw frequencies up and up with little regard for timing penalties.
The GL752VY uses an i7-6700HQ or i7-6820HK - the iMCs in both of these processors are rated to sustain 34.1GB/s on two channels of DDR4-2133, LPDDR3-1866, or DDR3L-1600.
Faster memory (DDR4-2400/-2666/etc) can be installed in any Skylake system, although it will default to JEDEC DDR4-2133 settings. The DDR4 itself will report any XMP profile(s) stored on its SPD firmware, but they will only work if supported across all system firmware and software - so basically if your BIOS allows the user to change memory voltages/timings then it can support faster DDR4, but if it doesn't allow any user changes then it'll only run the JEDEC defaults native to your processor.
These particular Skylake parts are Intel's lower/mid bins. It may turn out that actual memory bandwidth gains are minimal (or capped around 34.1GB/s) even if do manage to install and configure fully stable DDR4-2400/2666/etc with tight timings and no thermal throttling (because, yeah, any laptop including your mighty ROG laptop has very constrained thermal limits). Opinions differ, but I personally think DDR4-2133 is the right fit for your system and any increased performance from higher-frequency DDR4 will be noticeable only in benchmark brag and swag, not in any real-world actual usage, games, and applications. A dual-channel DDR4-2133 kit with the lowest possible timings would probably work out better, more efficient use of the Skylake's memory bandwidth, no XMP (ie: memory overclocking) instabilities or complications.
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I had a totally different experience with my G751. There are no settings in the BIOS to change anything memory related. I pulled all of the stock sticks PC3-12800(1600Mhz) and replaced them with DDR3L PC3-1600 (2133Mhz) and the BIOS reflected the change and the SPD was read and applied without doing a thing it went to 2133Mhz.