https://us.community.samsung.com/t5/Monitors-and-Memory/Samsung-990-PRO-2TB-Performance-Degradation-After-7B2QJXD7/m-p/3404469#M17545 <P>I'll be honest...I've kind of enjoyed benchmarking and beginning to understand how the variable size SLC cache affects results, but I've come to the conclusion that what I was seeing (except for the different Power On Hours between the 2TB and 4TB Pro's -- that's a puzzler!) is due to the design of the 2TB HW &amp; FW and the size of the SLC cache with ~57% utilization.<BR /><BR />If the M2_1 slot really was an issue, I would expect to see throttling under high-load scenarios, both poor burst and sustained performance, lower sequential write speeds, more system errors or drive disconnects (although I did suffer ~25 system crashes since the February build, but the&nbsp; 7B2QJXD7 firmware is supposed to directly address that issue), and, maybe thermal throttling alerts.&nbsp; So, yeah, I'm not going to swap the 2TB and 4TB drives -- my new NVMe Gen5 system drive should be arriving shortly, and that's enough swapping for me.<BR /><BR />Interesting to note, though:&nbsp; the M2_1 slot of the AsRock X870E Taichi is the only slot to support PCIe 5.0 and the only slot that is direct-to-CPU.&nbsp; Unfortunately, the motherboard design routes some heat through the slot and its heatsink, explaining why my 990 Pro 2TB consistently shows higher idle temps than the 4TB (typically 40-50C vs 30-40C):&nbsp;&nbsp;<A href="https://www.reddit.com/r/ASRock/comments/1ha3c9j/comment/mva0zow/" target="_blank">https://www.reddit.com/r/ASRock/comments/1ha3c9j/comment/mva0zow/</A>&nbsp; But, even so, I've never measured temperatures beyond ~68C on the 990 Pro 2TB during benchmarking, and smartctl shows no critical temp events.<BR /><BR />Thanks for helping me better understand the issues here; again, apologies for raising a fuss over something that is likely by design.<BR /><BR /></P><P>&nbsp;</P><P>&nbsp;</P> Tue, 11 Nov 2025 23:11:54 GMT SFdrifter 2025-11-11T23:11:54Z