The Steam Deck specifications have changed and no one has noticed until now

Anyone who purchased one of the consoles Steam Deck from Valve at launch, got a very special model of solid state drive installed in their device. Anyone who recently purchased a console received a different type of disc, potentially slower 

As reported by Hardwareluxx, everyone Steam Deck, which originally came with 256 or 512 GB SSDs, were connected using four "lanes". Now, some devices come with drives that only connect via two "lanes", a change that could theoretically result in performance degradation since you're effectively halving the drive's bandwidth. 

This change was not publicly announced in a press release or statement, and Steam Deck, which came with these new discs, were not distinguished by new model numbers. Indeed, the only public mention of this change came when Valve quietly edited the PDA's spec page in late May. 

So the only way to know if you have the original faster SSD installed in Steam Deck or not, is to check its characteristics in the system menu. 

It should be clarified that there are no tests that would confirm a decrease in performance with "dual-strip" drives, so we don't know for sure whether it really affects performance in any way. 

Source: Kotaku