Asus Z490-E issues with M2 and SATA ports causing confusion
Asus Z490-E issues with M2 and SATA ports causing confusion
The reference image shows the setup described. On most systems, the video card uses x16, while placing the M2 in the second slot provides an extra x4 bandwidth but removes two SATA ports, leaving four functional ports. If you swap the M2 from the second to the first slot, the manual states only one SATA port is disabled when running in SATA mode. This would likely force the card to operate at x4 instead of its intended x16. The first M2 slot can only be used in SATA or x4 mode; it doesn’t automatically switch to x8. To keep the card at 16x, you’d want to avoid using the first slot for M2 if possible.
The primary PCIe connections are using CPU lanes, while M.2 and SATA are handling chipset lanes separately. They don't interfere with each other. In M.2_2, two lanes overlap with SATA ports, and M.2_1's built-in SATA port connects to SATA_2. This setup is described in the manual as allowing one SATA port to be disabled when M.2 operates in SATA mode. If you need full x4 performance, it’s feasible. Running at x4 on the first slot can indeed force the graphics card to revert to 8x. Four lanes on either M.2 don’t impact PCIe1. The first M2 slot is restricted to either SATA or x4 mode only; it cannot support both simultaneously and would limit the graphics card. Using it in SATA mode is preferable to avoid conflicts.
The manual indicates flexibility in mixing the 1/2 columns. This means you could have a video card at x16, the second M2 slot at 4x (with two SATA ports disabled), and the first M2 slot also at 4x (without disabling anything). Alternatively, both M2 slots could be at 4x but lose one SATA port at 4x, keeping one M2 at 2x while using all SATA ports on the other. If you choose the first option, all SATA ports remain active. Bandwidth should still be shared with any connected SATA devices, so avoid disabling ports unless necessary for performance.
Oh hey, didn't realize it was the same OP! Yep, if I understand correctly, all 3 combinations draw from separate resource pools, so you can mix and match as you please within those restrictions.
I remain uncertain since the original image left out some details at the bottom. The text indicates that the SATA ports become disabled specifically when the second slot operates at 4x speed, not merely because it is filled. It seems these lanes might be combined rather than separate. Would you like me to clarify this further?
Reviewing other manuals, the 1/2 configuration can be combined. This implies the first slot doesn't share bandwidth and won't remove SATA2, provided it uses PCI Express X4. Both slots can operate at X4, but disable two SATA ports. All M2 slots and all six SATA ports are feasible, though the second M2 only supports 2x and shares bandwidth with two SATA ports. There are reports of issues such as slower PCI Express performance when SATA ports are disabled or M2 slots getting stuck at 2x. The practical implementation may have limitations beyond what is described.