Beware of the single rank x16 RAM kits sneaked in some laptop models! The 1Rx16 modules have significantly lower bandwidth compared to the 1Rx8 variants
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Thanks to the thorough reviews posted on Youtube by Jarrod’s Tech for the Lenovo Legion 5 Pro and the Asus ROG Strix G15 Advantage Edition, we were made aware that laptop OEMs could sometimes limit the laptop performance by sneaking some sub-par default RAM kits. Now, when asked about the reason behind these limitations, Asus blamed the ongoing shortages, which essentially forces them to supply the best RAM kits only for the more expensive models. Unfortunately, laptop OEMs do not want you to know this and do not mention any characteristics for the RAM kits to easily spot the slower modules, so end users need to rely on review channels in order to make an informed purchase. Cannot really find the review for the model you are set on buying? Just ask the OEM if the RAM modules are single rank or dual rank. You do not need to worry if the kits are dual rank. However, if the kits are single rank, you need to make sure they are x8 and not x16. Here is why.
It might sound counterintuitive at first, but the x8 modules have a better internal configuration made up of four bank groups, whereas the x16 chips only have two bank groups. Because of how modern day memory controllers work, the x8 configuration can yield considerably higher bandwidths compared to the x16 configuration. This becomes apparent when we inspect the secondary timings that are not usually mentioned by memory producers. Rule of thumb here is that memory commands take longer to execute in the same bank group than if spread through different bank groups, hence it is really beneficial to have more bank groups like the x8 configuration. The time difference between the same group commands and the different group commands varies, but it is usually at least 33% lower for different group commands (up to around 60% in some cases). Apparently, the Ryzen-based laptops are very susceptible to this sort of timing fluctuations, and Jarrod’s reviews, which were more recently complemented by a Linus Tech investigation, show that single rank x16 RAM kits could reduce FPS counts by 25% in some games. Still, content creation performance will only take a 5-10% hit most of the time.
The only real advantage for the x16 configuration is OEMs can save some PCB space (50% fewer memory chips), but that only applies to embedded RAM solutions (a.k.a. soldered RAM), so not particularly helpful in the case of laptops that allow users to replace the RAM modules. If the OEMs cannot reveal any details about the RAM kits, users should at least make sure the RAM is not soldered so they can eventually supply faster modules themselves.