X670E M.2_1 vs M.2_2 speed difference for SA builders

Quick Answer

On X670E boards, M.2_1 (CPU-direct) runs at PCIe 4.0 x4 (up to 7,000 MB/s) while M.2_2 typically routes through the X670E chipset at PCIe 4.0 x4 as well — but shared with other chipset bandwidth. In practice, M.2_1 delivers 3–8% better sustained sequential performance due to lower latency, while random read/write performance is nearly identical. Install your OS and primary game drive in M.2_1; secondary storage can go in M.2_2.

X670E M.2 Lane Architecture

X670E uses a dual-die chipset (two X670 silicon dies connected internally). The lane architecture for M.2 slots varies by board:

M.2_1 (all X670E boards): CPU-direct PCIe 4.0 x4 — fastest and most consistent; 3–5 ms lower latency than chipset-connected slots.

M.2_2 (most X670E boards): Chipset-connected PCIe 4.0 x4 — shares bandwidth with SATA, USB 3.2, and other chipset peripherals during heavy multi-device activity. Throughput may drop 200–400 MB/s under heavy concurrent I/O.

M.2_3 and M.2_4 (high-end X670E boards only): Chipset-connected PCIe 4.0 x4 — same as M.2_2, with potential for additional bandwidth sharing.

When the Slot Choice Matters in Practice

For gaming (game loading, texture streaming): slot difference is imperceptible — games load 0.1–0.5 seconds faster in M.2_1 vs M.2_2 in controlled tests. For content creation (sustained video capture, render output): M.2_1's dedicated CPU bandwidth provides 500–800 MB/s better sustained write performance during heavy multi-device workloads. For typical SA gaming builds: install Windows + games in M.2_1 and use M.2_2 for secondary storage or game overflow.

FAQ

Does installing a Gen 4 NVMe in M.2_2 on X670E hurt gaming performance?

Minimally — the slot difference translates to 0.1–0.5 seconds in game load times and is imperceptible during gameplay. M.2_2 on X670E is perfectly adequate for game storage. The performance gap matters more in creator workloads than gaming.

Can I install a Gen 5 NVMe in the M.2_1 slot on X670E and get Gen 5 speeds?

Only if your X670E board's M.2_1 slot is wired for PCIe 5.0 x4 (check board spec sheet). Most X670E M.2_1 slots are PCIe 4.0 x4 — a Gen 5 drive installed there runs at Gen 4 speeds (7,000 MB/s). Boards with native Gen 5 M.2 include the ASUS ROG Crosshair X670E Hero.

What NVMe drives are best for M.2_2 secondary storage on an X670E SA build?

A Samsung 980 Pro or WD Blue SN580 1–4 TB in M.2_2 is ideal for secondary game storage. Both cost R700–R4,500 depending on capacity at Evetech, and run at 3,500–7,000 MB/s in the chipset-connected slot — more than sufficient for game streaming.